text:
NES Programming

This book is an open work designed for people interested in learning to program for the NES (Nintendo Entertainment System).

Hardware specifications

 * CPU - Ricoh 2A03 CPU which is a MOS 6502 without a decimal mode.
 * Clocked 1.789773Mhz for NTSC (System 21.47727Mhz / 12) and 1.773447Mhz for PAL (System 26.601171Mhz / 15)
 * Memory - 2 KB
 * Video
 * Ricoh 2C02 PPU (Picture Processing Unit)
 * Resolution - 256 x 240 pixels (Only 256 x 224 pixels are visible on NTSC)
 * Colors - Fixed 52 (44 colors, 5 grays and 3 duplicated)
 * Palette
 * Background: 4 Palettes x 3 Colors + 1 Back Color
 * Sprites: 4 Palettes x 3 Colors
 * Tiles - 8 x 8 pixels tiled background
 * Sprites - Up to 64 8x8-pixel or 8x16 pixel sprites but only 8 can be displayed per scan-line
 * Sound
 * 2 Pulse wave channels
 * 1 Triangle wave channel
 * 1 Noise channel
 * 1 DPCM channel

Tutorials

 * Introduction: A few words on assembly
 * /Initializing the NES/

Appendices

 * The NES memory map

Hardware I/O ports
The NES has I/O ports located at addresses $2000-$2007 (hexadecimal) and $4000-$4017.

PPU

 * $2000 - write only - PPU Control Register 1
 * $2001 - write only - PPU Control Register 2
 * $2002 - read only - PPU Status Register

Video control

 * Sprites
 * $2003 - write only - Sprite Memory Address
 * $2004 - read / write - Sprite Memory Data
 * $2005 - write only - Background Scroll

PPU (continued)

 * $2006 - write only - PPU Memory Address - indexing into PPU memory location
 * $2007 - read / write - PPU Memory Data - data to read from a PPU memory location or write to a PPU memory location

Sound

 * Square wave 1
 * $4000 - Register 1 - Bits:
 * 0-3: volume / envelope decay rate
 * 4: envelope decay disable
 * 5: length counter clock disable / envelope decay looping enable
 * 6-7: duty cycle type (unused on noise channel)
 * $4001 - Register 2 - Bits:
 * 0-2: right shift amount
 * 3: decrease / increase (1/0) wavelength
 * 4-6: sweep update rate
 * 7: sweep enable
 * $4002 - Register 3 - Bits:
 * 0-7     Eight LSB of wavelength
 * $4003 - Register 4 - Bits:
 * 0-2: 3 MSB of wavelength (unused on noise channel)
 * 3-7: length counter load register
 * Square wave 2
 * $4004 - Register 1 - Same as Square wave 1
 * $4005 - Register 2 - Same as Square wave 1
 * $4006 - Register 3 - Same as Square wave 1
 * $4007 - Register 4 - Same as Square wave 1
 * Triangle
 * $4008 - Register 1 - Bits:
 * 0-6 	linear counter load register
 * 7	       length counter clock disable / linear counter start
 * $4009 - Unused Register
 * $400A - Register 3 - Same as Square wave 1
 * $400B - Register 4 - Same as Square wave 1
 * Noise
 * $400C - Register 1 - Same as Square wave 1
 * $400D - Unused Register
 * $400E - Register 3 - Bits:
 * 0-3	 playback sample rate
 * 4-6	 unused
 * 7	random number type generation
 * $400F - Register 4 - Same as Square wave 1

DMC

 * $4010 - Register 1 - Bits:
 * 0-3: sample rate
 * 4-7: unused?
 * $4011 - Register 2 - Bits:
 * 0-7: volume
 * $4012 - Register 3 - Bits:
 * 0-7: voice table start address(N*0x40+0xc000)
 * $4013 - Register 4 - Bits:
 * 0-7: voice table byte size(N*16+1)

Sprites (continued)

 * $4014 - write only - DMA Access to the Sprite Memory

Sound (continued)

 * $4015 - read / write - enable/disable individual sound channels

Joystick

 * $4016 - read / write - Joystick 1
 * $4017 - read / write - Joystick 2

title: NES Programming


text:
Talk:School Science

Wikipedia edit history

 * 03:37, 2005 Apr 20 Egil (vfd - should be moved to wikibooks)
 * 00:57, 2004 Dec 23 Michael Hardy m
 * 21:13, 2004 Mar 2 Theresa knott (revert otherwise you break the link)
 * 20:00, 2004 Mar 2 User:209.129.254.82 (Added the s inside the bracket to bell jar model lungs)
 * 19:12, 2004 Jan 6 Michael Hardy (Don't use gratuitous capitals.)
 * 19:12, 2004 Jan 6 Michael Hardy
 * 19:11, 2004 Jan 6 Michael Hardy
 * 19:11, 2004 Jan 6 Michael Hardy
 * 08:34, 2003 Aug 18 Theresa knott (added charles law tubes)
 * 10:42, 2003 Apr 25 Snowy
 * 21:42, 2003 Apr 14 Theresa knott m
 * 14:57, 2003 Mar 14 User:194.74.199.58
 * 14:55, 2003 Mar 14 User:194.74.199.58
 * 14:13, 2003 Feb 26 Theresa knott m (Decapitalising links)
 * 21:33, 2003 Feb 24 Theresa knott m
 * 18:44, 2003 Feb 18 Theresa knott m
 * 15:02, 2003 Feb 17 Snowy
 * 14:18, 2003 Feb 14 Snowy

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:School Science


text:
School Science

This book provides experiments and demonstrations, as well as academic background, on science suitable for schools. Do not assume that everything is safe! Most will have some sort of safety advice on the page but the absence of written precautions does not mean that you can just go and play ahead. If you are an adult, you should use your own judgement and common sense. If you are a minor (child), it is highly recommended that you should ask for more advice and help from your teachers and parents.

Introduction to science

 * Electricity
 * /Types of Electric Circuit/

School physics experiments and demonstrations

 * /How to make a transformer/
 * /Westminster motor kits/
 * /Atmospheric pressure demonstration/
 * /Hydraulics demonstration/
 * /The Indian rope trick (magnetism)/
 * /Demonstrating properties of waves with a ripple tank/
 * /Demonstrating the properties of waves on an Oscilloscope/
 * /Rotational Inertia Experiment/

School biology experiments and demonstrations

 * /How to prepare an onion cell slide/
 * /Staining onion cells without methylene blue/
 * /Nail varnish impressions of stomata/
 * /Paper chromatography of amino acids/
 * /Screaming jelly babies/
 * /Testing leaves for starch/
 * /Using water snails and pond weed to investigate the carbon cycle/
 * /Winkler test for dissolved oxygen/
 * /Osmosis demonstration/
 * /Apparatus for demonstrating osmosis/ using visking tubing
 * /Bell jar model lung/s
 * Showing CO2 is produced by respiration using Huff'n'Puff
 * Measuring transpiration with a Potometer
 * /Demonstrating the effects of amylases on starch/
 * /Oyster cultivation in seawater ponds/
 * /Frog dissection/

School chemistry experiments and demonstrations

 * /Flour bomb/ demonstration
 * /Flour fire ball/
 * /Screaming jelly babies/
 * /Cannon fire/
 * /Lemon Battery/
 * /Creating chemical solutions/

Constructing school science lab equipment

 * /Microscope slide/
 * /Agar plate/
 * /Cell holder/
 * /Gram staining/
 * /Bulb holder/
 * /Simple switches/
 * /Conductivity test/
 * /OHP coil/
 * /Friction blocks/
 * /Hydraulics demonstration/
 * /Angular momentum apparatus/
 * /Demo periscope/
 * /Graticule slides/
 * /Bell jar model lung/s
 * /Model of the plough/
 * /Apparatus for demonstrating osmosis/
 * /Torque demonstration/
 * /Making Charles' law tubes/
 * /Mercury cleanup/

School science technician
In schools, the science technician is the person who prepares the practical equipment and makes up the solutions used in school science labs. The role also includes instructing and assisting teachers with practical skills, including class demonstrations, for advanced techniques across all disciplines. Many are very well qualified and have degrees, such as a Bachelor's degree (B.A. or B.Sc.) or Master's degree (M.Sc.) and/or other professional qualifications such as the HNC, HND and NVQ.

Their main duties include:
 * /Care of living organisms/
 * Making up solutions
 * School science experiments and demonstrations
 * Inventory
 * Stock control
 * Budget and Accounts
 * Repairing and constructing lab equipment

title: School Science


text:
Cookbook:Homemade Tempeh

| Fermented food recipes

Tempeh is a traditional Indonesian food made from soybeans. It is a fermented food, utilising a special type of mould that forms a cake. When fresh, tempeh has a nice mushroom-like smell and flavour.

Ingredients

 * 400 grams (14 ounces) dried soybeans
 * Water
 * 2 tablespoons cider vinegar
 * 1 teaspoon tempeh starter (or ragi tempe)

Equipment

 * Pressure cooker or saucepan, at least 3 litres (3 quarts)
 * Large tray (or trays) for spreading cooked beans on to dry
 * Banana leaves, zip-lock bags or shallow dishes for incubating the fermenting tempeh
 * Somewhere warm to incubate the tempeh at about 30–35°C / 86–95°F (e.g. your oven, with the light on)
 * Thermometer (optional) for keeping a watch on the temperature of the incubator

Procedure

 * 1) Cover soybeans with water, and soak overnight or at least 12 hours.
 * 2) Remove the hulls (i.e. skins) from the beans by rubbing between both hands (see notes).
 * 3) Skim off most of the hulls either by washing them away or by using a skimmer or strainer. Some hulls may be left behind without affecting tempeh quality.
 * 4) Cook beans until just tender, not mushy; undercooked is best for tempeh (see notes).
 * 5) Drain beans, and spread to dry somewhere with airflow (see notes).
 * 6) Collect beans into a bowl, and mix in the cider vinegar. This acidifies the beans slightly, inhibiting unwanted spoilage organisms during fermentation.
 * 7) Sprinkle the tempeh starter over the beans and mix in well (see notes).
 * 8) Pack the beans loosely into banana leaves, zip-lock bags, or shallow dishes for incubating. Zip-lock bags must be punctured at roughly 1 cm (½ inch) intervals to keep oxygen up to the fermenting beans.
 * 9) Load the soon-to-be tempeh into your incubator, preferably on racks that will allow air circulation. An electric oven with a light on makes a pretty good incubator, because the light provides just enough heat to keep the beans warm while the fermentation starts happening.
 * 10) Incubate for 12 hours or so at around 30–35°C (86–95°F) with a heat source (unless it's already that hot where you are).
 * 11) After 12 hours, remove or turn off the heat source - the fermenting beans will be making their own heat, and may overheat if you keep them too warm.
 * 12) Monitor periodically from then on, and remove when the beans are totally consumed by fluffy white tempeh with no gaps.
 * 13) After fermentation is complete, serve straight away in your favourite tempeh recipe, refrigerate for two to three days, or freeze for up to two months.

Notes, tips, and variations

 * Tempeh can be made from almost any legume (beans, chickpeas, split peas), most grains, and some nuts. Soybeans are probably one of the cheapest beans to use, but more flavoursome beans make more flavoursome tempeh!
 * Tempeh can also be made from okara, the presscake left over from making soy milk and tofu. In Indonesia, this is called tempe gembus.
 * There are many ways to remove the hulls or skins from the beans, including:
 * cracking dried beans in a grain mill and winnowing to remove hulls
 * grinding soaked beans in hands
 * rubbing soaked beans between both hands
 * rubbing cooked beans between both hands (but don't get burnt!)
 * buy them pre-hulled - e.g. chana dal, split fava beans, split peas
 * Soybeans can be cooked easily in a pressure cooker at 15psi for 10 minutes with slow-release method, or on a rolling boil for 30 minutes in a saucepan. Soft, ready-to-eat soybeans are not the target here, so don't cook too long.
 * It can be difficult to distribute the teaspoonful of tempeh starter through the beans evenly. To make the job a little easier, mix the tempeh starter into a couple of tablespoons of rice flour first, then sprinkle and stir this mixture into the beans a little at a time.

id:Resep:Tempe

title: Cookbook:Homemade Tempeh


text:
Talk:School Science/Cell holder

Wikipedia edit history

 * 19:14, 2004 Jan 6 Michael Hardy
 * 05:36, 2003 Nov 17 Jerzy m (relink to battery (electricity) per disamb rename)
 * 17:18, 2003 Nov 14 Reddi m
 * 17:11, 2003 Nov 14 Reddi m
 * 16:54, 2003 Nov 14 Reddi m
 * 16:52, 2003 Nov 14 Reddi m (-border:1px; border-style:solid;)
 * 16:51, 2003 Nov 14 Reddi m (mv imgs)
 * 16:51, 2003 Nov 14 Reddi m (img frmts)
 * 15:55, 2003 Oct 3 User:80.0.18.185
 * 14:38, 2003 Apr 8 Snowy
 * 14:30, 2003 Mar 17 User:217.168.172.214 (laboritories -> laboratories)
 * 14:17, 2003 Mar 17 Theresa knott m (formatting and wikifying)
 * 13:55, 2003 Mar 17 Snowy
 * 13:52, 2003 Mar 17 Snowy
 * 09:38, 2003 Mar 14 User:194.74.199.51
 * 09:37, 2003 Mar 14 User:194.74.199.51
 * 09:20, 2003 Mar 14 User:194.74.199.51
 * 09:18, 2003 Mar 14 User:194.74.199.51
 * 15:39, 2003 Mar 12 User:194.74.199.59

title: Talk:School Science/Cell holder


text:
School Science/Cell holder

A cell holder is a simple device for holding 1.5V cells {batteries} for use in school laboratories. A cost-effective way of making simple cell units to use with 4mm leads, follows.

See also: ../Bulb holder, ../Simple switches.

Equipment Required (to Make 60 Cell Holders)

 * 60 pieces of wood at least 120mm x 36mm and 20mm thick
 * 'D' cell plastic holder (available from most Design & Technology suppliers)
 * 4mm terminals, 60 black and 60 red (available from most electrical component retailers)
 * small screws to fit through the base of the cell holders
 * Extra flexible lead wire, black and red
 * Solder + soldering iron
 * Pliers
 * Screwdriver
 * Drills 7.5mm, 5mm & 3mm
 * Countersink drill bit
 * Solder Flux

Fig. 1 Cell Holder Diagram Fig. 2 Cell Holder Complete with Cell

Method for making the cell holders

 * 1) Get the wood cut the wood to the correct size and sanded if need be.
 * 2) Drill 2 x 7.5mm holes at either end as show in fig 1.
 * 3) Drill 2 x 5 mm holes near those.
 * 4) Countersink the larger holes to about half way, so that you can attach the nut of the 4mm terminals.
 * 5) Insert the 4mm terminals in the larger holes, one of each colour in either end, and secure with nut.
 * 6) Attach the plastic cell holder with the 2 screws (diagonally opposite), first drilling holes, and making sure that the end with the spring goes near the black terminal.
 * 7) Cut a 5cm piece of each wire, strip the ends and solder onto the tags on the plastic cell holder, making sure you do not take to long or the tags will melt off. Ensure you have got red wire to the red terminal and black wire going to the black terminal. Then push the wire through the 5mm hole and out the other side so you can then solder it onto the 4mm terminal.
 * 8) It should look something like fig 2. these are usually very durable and can be used in conjuction with bulb holders etc.

title: School Science/Cell holder


text:
Talk:School Science/Bulb holder

Wikipedia edit history

 * 17:02, 2003 Nov 14 Reddi m (See also)
 * 17:01, 2003 Nov 14 Reddi m (img frmt)
 * 15:58, 2003 Oct 3 User:80.0.18.185
 * 10:39, 2003 Apr 25 Snowy
 * 19:40, 2003 Apr 13 User:195.92.198.72 (fixed link to drill wikified MES bulb)
 * 12:43, 2003 Apr 11 User:217.37.214.121 (3.5V light bulbs)
 * 12:35, 2003 Apr 11 Snowy
 * 14:37, 2003 Apr 10 Snowy

title: Talk:School Science/Bulb holder


text:
School Science/Bulb holder

A bulb holder is a simple device for holding 3.5V bulbs for use in school laboratories. A cost-effective way of making bulb units to use with 4mm leads, follows.

See also: ../Cell holder

Equipment Required (to Make 60 Bulb Holders)

 * 60 pieces of wood at least 120mm x 36mm and 20mm thick
 * plastic bulb holders to hold MES bulbs (available from most Design & Technology suppliers)
 * 4mm terminals, 60 black and 60 red (available from most electrical component retailers)
 * small screws to fit through the bulb holders
 * Extra flexible lead wire, black and red
 * Solder + soldering iron
 * Pliers
 * Screwdriver
 * Drills 7.5mm, 5mm & 3mm
 * Countersink drill bit
 * Solder Flux

Fig. 1 Bulb Holder Diagram Fig. 2 Bulb Holder complete with Bulb

Method for making the bulb holders

 * 1) Get the wood cut the wood to the correct size and sanded if need be.
 * 2) Drill 2 x 7.5mm holes at either end as show in fig 1.
 * 3) Drill 2 x 5 mm holes near those.
 * 4) Countersink the larger holes to about half way, so that you can attach the nut of the 4mm terminals.
 * 5) Insert the 4mm terminals in the larger holes, one of each colour in either end, and secure with nut.
 * 6) Attach the plastic bulb holder with the 2 screws, first drilling holes.
 * 7) Cut a 6cm piece of each wire, strip the ends and solder onto the tags on the plastic bulb holder. Ensure you have got red wire to the red terminal and black wire going to the black terminal. Then push the wire through the 5mm hole and out the other side so you can then solder it onto the 4mm terminal.
 * 8) It should look something like this. see fig 2. these are usually very durable and can be used in conjuction with cell holders etc.

title: School Science/Bulb holder


text:
Talk:School Science/Simple switches

Wikipedia edit history

 * 13:44, 2004 Feb 23 Nilmerg m (fix link)
 * 17:17, 2003 Nov 14 Reddi m
 * 17:15, 2003 Nov 14 Reddi m
 * 14:46, 2003 Oct 1 User:194.74.199.42
 * 13:43, 2003 Apr 25 Snowy

title: Talk:School Science/Simple switches


text:
School Science/Simple switches

A single switch is a simple device for showing single pole single throw (SPST) switches for use in school laboratories. A cost-effective way of making simple switch units to use with 4mm leads, follows.

See also: ../Cell holder

Equipment Required (to Make 30 Single Switches)

 * 30 pieces of wood at least 150mm x 40mm and 7mm thick
 * 60 pieces of 0.1mm copper foil (available from most Chemical suppliers) cut into 10mm x 70mm strips and 10mm x 25mm strips.
 * 4mm terminals, 60 black and 60 red (available from most electrical component retailers)
 * 120 drawing pins
 * Extra flexible lead wire, black and red
 * Solder + soldering iron
 * Pliers
 * Screwdriver
 * Drills 7.5mm & 5mm
 * Solder Flux
 * 60 pieces of wood for feet (optional)

Fig. 1 Simple Switch Diagram  Fig. 2 Simple Switch

Method for making the switches

 * 1) Get the wood cut the wood to the correct size and sanded if need be.
 * 2) Drill 2 x 7.5mm holes at either end as show in fig 1.
 * 3) Drill 2 x 5 mm holes near the larger holes as in fig 1.
 * 4) attach the larger piece of foil to the wood using the drawing pins, as shown in fig 1. Then bend it over slightly where the drawing pins are.
 * 5) attach the smaller piece of foil to the wood using the drawing pins. as shown in fig 1.
 * 6) Insert the 4mm terminals in the larger holes, one of each colour in either end, and secure with nut.
 * 7) Cut a 50mm piece of each wire, strip the ends and solder onto the 2 pieces of copper foil. as in fig 2. Ensure you have got red wire to the red terminal and black wire going to the black terminal. Then push the wire through the 5mm hole and out the other side so you can then solder it onto the 4mm terminal.
 * 8) It should look something like this. see fig 2. these are usually very durable and can be used in conjuction with cell holders and bulb holders etc.

title: School Science/Simple switches


text:
School Science/Hydraulics demonstration

This article explains how to demonstrate the principles of hydraulics.

A good way of demonstrating the basic principles of hydraulics is to join two syringes together with rubber tubing to make an watertight seal [see figure 1]. The syringes can be filled with water, oil, or just air. Pushing plunger A causes plunger B to move out and pushing plunger B in causes plunger A to move out. This works even if the syringes are not in the same plane. i.e. if the tubing is bent by 90° as long as there is no kink in the tube that prevents the free flow of fluid.

With syringes of different sizes it is possible to demonstrate how to multiply force [see figure 2]. A small mass on a small syringe can lift a much larger mass if it is resting on a bigger syringe. This is because the pressure in the two syringes is equal, but the surface areas of the two pistons are different, and force = pressure × area.

title: School Science/Hydraulics demonstration


text:
Talk:School Science/Hydraulics demonstration

Wikipedia edit history

 * 20:13, 2004 Nov 18 Tosta Dojen m (typo)
 * 08:14, 2004 Aug 26 Costyn m (→See Also - format)
 * 14:28, 2004 Jun 10 User:68.229.240.25 ("adjusting the size of the syringes" -- not possible, deleted)
 * 19:09, 2004 Jan 6 Michael Hardy
 * 17:21, 2003 Nov 14 Reddi m
 * 17:08, 2003 Nov 11 Reddi m
 * 14:56, 2003 Jun 9 Theresa knott m
 * 14:36, 2003 Feb 26 Heron (completed the sentence)
 * 12:34, 2003 Feb 26 Theresa knott m (Tiny format)
 * 11:42, 2003 Feb 26 Snowy
 * 16:13, 2003 Feb 22 Theresa knott m (aligning the diagrams with the text)
 * 14:46, 2003 Feb 19 Theresa knott (Adding diagrams. The word dont wrap around as I would like. The page needs to be formatted as a table but I don't know how to do it.)
 * 14:37, 2003 Feb 19 Theresa knott


text:
Talk:School Science/Graticule slides

Wikipedia edit history

 * 16:34, 2004 Nov 15 Matthew Stannard m (Please help out by clicking here to fix someone else's Wiki syntax)
 * 16:32, 2004 Nov 15 Matthew Stannard m
 * 16:32, 2004 Nov 15 Matthew Stannard m (Please help out by clicking here to fix someone else's Wiki syntax)
 * 00:39, 2003 Nov 15 Theresa knott m (typo)
 * 17:44, 2003 Nov 14 Reddi m
 * 17:42, 2003 Nov 14 Reddi m
 * 17:41, 2003 Nov 14 Reddi m
 * 17:40, 2003 Nov 14 Reddi m
 * 17:40, 2003 Nov 14 Reddi m
 * 17:37, 2003 Nov 14 Reddi m
 * 17:37, 2003 Nov 14 Reddi m
 * 11:53, 2003 Apr 28 Theresa knott m (Microsoft word -->Microsoft Word)
 * 12:51, 2003 Mar 19 Theresa knott m
 * 12:47, 2003 Mar 19 Theresa knott (Added a small graphic and tidied up a bit)
 * 19:34, 2003 Feb 18 Theresa knott

title: Talk:School Science/Graticule slides


text:
School Science/Graticule slides

A graticule slide is a microscope slide that contains a mm grid of lines. They allow the size of objects seen under magnification to be measured. A simple version of a graticule slide can be made by anyone with access to a drawing program. Something as simple as the drawing tools that come with Microsoft Word will do (see instructions below).

Fig. 1 vector rasterized grid (low quality)

Once there is a suitable grid on the computer [you could download the one to the side; see figure 1], a test print should be produced. The size of the printed square should be measured and the grid should be resized until a cm2 grid is printed. This grid can now be printed on photocopiable OHP sheets.

The OHP sheets can be glued to a glass slide with clear nail varnish.

Instructions to create a grid
Use of Word drawing tools (in italics)

 * 1) In Word, go to view, toolbars. and make sure that 'Drawing' is ticked. Then select a line from the drawing tool pallet. [it is a picture of a line next to 'AutoShapes']
 * 2) Draw a single straight, vertical line. Copy and paste the line 9 times.
 * 3) Use the arrow keys on the keyboard to line up the lines so that you have 10 evenly spaced lines.
 * 4) Select all ten lines at once by holding down the shift key and left clicking on each line in turn.
 * 5) Go to Draw then Group, to group all ten lines into a single object.
 * 6) Copy then paste the lines then go to 'Draw' then 'Rotate or flip' and rotate by 90°
 * 7) Line up the vertical and horizontal lines and by using the corner tabs resize them until there is a perfect grid without any overhangs. Then select both sets of lines and group them together into one object.You should now have a square grid.

title: School Science/Graticule slides


text:
Talk:School Science/Apparatus for demonstrating osmosis

Wikipedia edit history

 * 14:19, 2005 Feb 27 SimonP m (Category:Science experiments)
 * 23:18, 2004 Mar 3 Naddy m (typo)
 * 17:56, 2003 Nov 14 Reddi m (intro)
 * 17:53, 2003 Nov 14 Reddi m (img; See Also)
 * 13:14, 2003 Jul 6 MyRedDice m (osmosis demonstration)
 * 16:28, 2003 Jun 28 User:62.254.128.6
 * 16:25, 2003 Jun 28 User:62.254.128.6
 * 16:22, 2003 Jun 28 User:62.254.128.6
 * 23:06, 2003 Apr 16 Theresa knott m (Adding links to osomis with eggs and potatos)
 * 22:59, 2003 Apr 16 Theresa knott (Diagram plus instructions on how this simple apparatus is assembled and used )

The opening paragraphs are simply wrong. Although Visking is a partially permeable membrane the molecular weight cut-off of Visking tubing is generally rated at 12-14kD. Sucrose or most other sugars would easily pass through this membrane which is why it is used as a model of the gut. That is starch is broken down by enzymes in the tube and sugars are allowed to pass through the membrane wall.

The osmosis experiment relates to something slightly different. It is the movement of water from a high water concentration to a low one, aiming ultimately to equilibrium. Should there be a higher concentration of sugar solution inside of the membrane then the tendency would be for the water molecules to come into the membrane and a rise in the level of liquid in the capillary tube, in plant cells this would result in turgidity. Although the osmotic potential (into the membrane rather than out) may stop the sugars escaping they are small enough to come out and the dyes may well be seen in the outside bath. Similarly if the tubing contains a smaller concentration of sugars on the inside than the outside one would expect water to come out of the membrane leading to flaccidity but the concentration on the outside needs to be substantially higher and the sugars may still go through.


text:
School Science/Apparatus for demonstrating osmosis

This apparatus for demonstrating osmosis through visking tubing (otherwise known as dialysis tubing) and is widely used in school. Visking tubing is a semipermeable membrane that allows small molecules likewater to pass through but does not allow larger molecules like sugar. If solutions of different concentration are on either side of the visking membrane, water molecules will pass through and tend to dilute the more concentrated solution.

The assembled equipment is inserted into hypotonic, hypertonic, and isotonic solutions and the level on the capillary rises, falls, or stays level accordingly. This apparatus is easy for school children to use, but is fiddly to set up. It can be set up by a technician in advance.

Apparatus

 * 0.5m length of capillary tube
 * 10cm of medium width visking tubing
 * Bung with hole. The bung and visking tubing should be selected so that the tubing just fits over the bung.
 * Rubber tubing (small and large bore)
 * 0.5M sucrose solution
 * Food dye e.g. cochineal.
 * Pipette

Apparatus for demonstrating osmosis (assembled) Notes: a) capillary tube b) rubber band c) bung d) rubber band e) sucrose solution with food dye f) knotted visking tubing

Setting up the Apparatus

 * 1) The visking tubing is softened under a running tap until it opens up. A knot should be tied at one end to make a bag.
 * 2) A bung that is just small enough to fit snugly inside the visking tubing is inserted into the unknotted end. Then a ring of a suitable bore rubber tubing is cut to make a band.This band is then slipped over the visking tubing so that it grips the tubing to the bung.
 * 3) The reason that food dye is added to the sucrose solution is to make the level in the capillary tube easy to see.
 * 4) The bag is filled completely to the brim with the coloured sucrose solution by squirting a pipette full at a time through the hole in the rubber bung. No air bubbles can remain. At this stage the knot and the attachment to the bung is checked for leaks.
 * 5) The capillary tubing is then carefully inserted into the bung. The fit needs to be tight and the sucrose should come up about half way (see diagram). If the level is too high the visking bag can be gently squeezed to force a little solution out of the top of the capillary. If the level is too low, a dialysis clip is attached just above the knot to reduce the volume of the bag.
 * 6) A ring from some narrow bore rubber tubing is cut and slippedover the capillary tube to act as a marker for the level.

Method of Use
A) Clamp the apparatus in a retort stand, then place into a large beaker of 0.5M sucrose (isotonic). Make sure the visking bag is hanging freely in the solution. I.e. not touching the sides or bottom. This stops it from being squashed and distorting the results.

B) Slide the rubber band to the top of the capillary level in order to mark the start position.Put the apparatus into 2.0M sucrose solution (hypertonic). The level in the capillary tube will fall as the water inside passes through the visking tubing in order to dilute the stronger solution outside.

C) Put the apparatus into distilled water (hypotonic). The level in the capillary tube will rise as the water passes into the visking bag to dilute the stronger solution inside.

Storage of the Apparatus
The apparatus cannot be stored for more than a few days with the sugar solution inside, because it will go mouldy. The capillary tube should be removed and thoroughly rinsed as any sugar left inside will harden and block the tube. The visking bags can be left attached to the bungs but should be rinsed and stored in water or a mixture of water and ethanol to keep the bag soft. If the visking dries out it may become brittle and crack.


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Talk:School Science/Making Charles' law tubes

Wikipedia edit history

 * 07:24, 2005 Apr 6 PeregrineAY m (wikied)
 * 05:29, 2005 Feb 2 User:12.221.162.10
 * 18:20, 2005 Jan 5 User:65.37.109.242
 * 00:52, 2004 Dec 23 Michael Hardy
 * 17:57, 2003 Nov 14 Reddi m (See also)
 * 09:50, 2003 Feb 22 Enchanter m (Fix link to mercury)
 * 20:56, 2003 Feb 13 Adrian Kirkup m
 * 12:12, 2003 Feb 12 User:213.253.40.129 (Charles' law)
 * 11:18, 2003 Feb 12 User:217.204.254.210
 * 11:09, 2003 Feb 12 User:217.204.254.210
 * 09:31, 2003 Feb 12 User:217.204.254.210 (minor edit addind degree sign)
 * 09:25, 2003 Feb 12 User:62.232.9.130


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School Science/Making Charles' law tubes

Charles' law tubes allow the demonstration of Charles' law in a school lab.

Heat the tube in boiling water, drying oven or with a hot air gun and place open end in clean mercury. Allow tube and the air in it to cool, drawing a thread of mercury about 5mm long up into the tube. Allow all to cool to room temperature. To move the thread of mercury further down the tube, to ensure it is not expelled when the tube is heated to 100°C during the experiment, pass a short length of nylon fishing line (approx 0.5mm diameter) down the tube and through the mercury. This allows the air below the mercury to leak out around the line and when the mercury has fallen to the required position, remove the nylon line. This should ONLY be done if one has proper safety training regarding the hazards of mercury and the school is equipped with proper mercury spill kits for containing and cleaning any potential spills.


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QBasic/Subroutines and Functions

Purpose
Subroutines and functions are ways to break up your code into reusable 'lumps'. They allow the programmer reuse a large set of common instructions just by calling the appropriate procedure or function.

For example, lets say you need to PRINT multiple Tables of values. One way to do this is to just enter all the Table PRINT commands directly into where you need them. However this not only makes the program very large but also makes it harder to debug or change the 'style' of the table. A simpler way is to create a single 'Print Table' procedure and enter all of the PRINT commands there. Then, each time you need to print a Table, you would simply 'call' the 'Print Table' procedure with a list of the values to be printed.

Procedure vs. Function
A procedure does something and does not return anything for the programmer. For example, a procedure might be used to set the screen mode and palette.

A function does something and RETURNS a value. For example, if you need to find the average of two values, you might write a function that takes in two numbers and returns the average.

GOTO and GOSUB
The GOTO and GOSUB statements were the original methods by which subroutines were created. They were most common on older basic implementations and are kept around for compatibility reasons; however, their use is not recommended in other programming languages or in large scale projects, both because GOTO's make it harder to 'follow' the program flow and because GOSUB's do not 'isolate' the changes made to any variables.

These two commands depend on Labels, which come in one of two forms. The first and older form involves writing line numbers at the beginning of each line (usually in increments of 10). The newer method looks similar to other programming languages, which is a single word followed by a colon.

The GOTO statement is simple; it just moves the execution point to a given Label:

The GOSUB statement transfers control to a given Label, however when a RETURN statement is encountered, execution returns to the line following the GOSUB statement. Any changes made within the GOSUB will be to actual variables used within the 'main' code.

ON ERROR
The ON ERROR allows you to define an error handler for your program; when an error occurs, it immediately jumps to the given label. The control returns once the program reaches a RESUME statement, which can either return control to the same point, the next statement, or any other desired label.

Within Qbasic, the error handler cannot be located within any subroutines. As such, any error checking or flags will have to be handled through the use of variables that are shared with the main module.

NOTE: If your error handling routine does not have a "resume" statement in it (IOW you try to do it all with gotos) error handling will only work once - the next "on error" will be ignored and the program ends as if you had no "on error" statement at all. This problem does not seem to be mentioned in any of the documentation. It took me three hours to figure out why two nearly identical program portions acted so differently.

Declaring a subprocedure
A superior method of declaring a subprocedure is using the SUB statement block, because (by default) any new variables used within the subprocedure are discarded on exit.

Under the QBasic IDE, doing so moves the SUB block to its own window to prevent accidental deletion of the module, and allows the easier organization of the program code.

Calling a subprocedure is as simple as writing the name of the subprocedure (passing any required parameters). If you want, you can use the CALL statement to indicate to other programmers that it is a subprocedure.

Whilst the Parameters passed into subprocedures are passed by 'reference' (i.e. they take on a new name within the SUB), any changes that are made to the values are 'reflected back' into the originals. By default, all other variables used within the SUB are discarded when the END SUB is reached (or an EXIT SUB is executed), except as below :-

To 'preserve' the values of variables used within the SUB for re-use on the next CALL, use the STATIC keyword at the end.

If you need access to a variable (that has not been passed as a parameter), use the SHARED keyword to define each at the start of the subprocedure (a SHARED variable retains its name).

Declaring a function
A function is a form of subroutine that returns a value. Everything that applies in defining a subroutine also applies to a function. Within the function, the return value is created by using the function name as a variable - the return value is then passed to the calling expression when a valid exit or end call is reached. There are two ways to return from a function, one way is to reach the END FUNCTION statement, the other is to make a call to EXIT FUNCTION. The difference between END FUNCTION and EXIT FUNCTION is that there can only be a single END FUNCTION and it must appear after all other code for the function as it denotes the end of a code block. EXIT FUNCTION can occur multiple times and can be placed anywhere deemed appropriate.

Functions are declared in the same way as variables - it returns the variable type it's defined to return, in the same way variables are defined to contain their specified type. By default, it is a number, but appending a dollar sign indicates that it is returning a string.

Functions can only be called within an expression; unlike subroutines, they are not a standalone statement.

title: QBasic/Subroutines and Functions


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Instructional Technology/Instructional Design/ADDIE

--ADDIE is an instructional model for teaching the Instructional Design process. The acronym corresponds with the five stages of instructional development: analysis, design, development, implementation, and evaluation. Each step of the model has an outcome that feeds information to the following steps.

 * Assessment should occur at the beginning of a project. During this stage, the instructional designer should consider optimals and actuals.  According to Allison Rossett, an expert on training needs assessment, actuals are what the current performance is and optimals are what should be happening, the desired performance. Once these are determined, it should be determined whether or not instruction is needed to fill the gap.  If instruction is needed, the instructional designer should continue the process.  If instruction is not needed, a Human Performance Technologist should be consulted.

 * Design happens after the assessment phase. This is where the objectives, assessment approach, exercises and content is specified.

 * Development is the phase in which the work takes place. User manuals/materials are created as well as instructor materials. The actual course is developed, whether it is an instructor led course, web-based course, or computer based training.

 * Implementation is the actual rollout of what was designed and developed. Providing the actual instruction/course to the learners.

 * Evaluation should be conducted throughout the phases in the form of formative evaluation. As formative evaluation is conducted, revisions are made to the instruction/design. Summative evaluation occurs at the end. Summative evaluation looks at the actual outcomes of the instruction, did the learners learn what they needed to know.

Advantages of Using ADDIE
Cost effective Saves time Promotes effective learning Consistent Effective in training

Criticisms of ADDIE
There are drawbacks to any large system or model and ADDIE is not different. ADDIE has been criticized for being: Too systematic Too dogmatic Too linear Too constraining Too time-consuming to implement --Nackj

Introducing a Rapid Prototyping Phase in ADDIE
For best results, the development process for CD-ROM or Web-based training programs should use a modified ADDIE model, which borrows from the most valuable aspects of the systemic approach. Specifically, a rapid prototype phase is inserted after, or as an extension of, the design phase. A rapid prototype is simply a quickly assembled module that can be tested with the student audience early in the ISD process. The evaluation typically looks at things like how well the learners responded to the creative metaphor, how effective the learning activities are, and how well the program performs on the chosen technology platform. Based on the feedback, the design can be revised and another prototype developed. This iterative process continues until there is agreement and confidence in the prototype.

In this process, only after the prototype is completed is additional development work done. However, this work often moves more quickly after a rapid prototype than in the traditional ADDIE model. Instructional designers and writers are able to proceed more efficiently since they know exactly what the program will look like and what it will be capable of doing. Additionally, with all of the major technical issues resolved, final programming becomes a simple matter of assembly of media components.


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Cookbook talk:Peanut Curry Sauce

Fish sauce is made from fish, therefore not vegetarian. Does anyone have a veggie version of this?

 * Other than being a bit salty, fish sauce is good for you. Fish contain omega-3 fatty acids. This isn't like eating a blackened hot dog.
 * Other animal products are also good for you. The question, I think, still stands.
 * Mix vegetable broth with a touch of soy sauce. A vegetable broth/sake reduction would be good too.

 * Cookbook:Fish Sauce (Vegan). You could probably exchange it for soy sauce or some other savory sauce like that as well... wouldn't be the same, but it's a start. Kellen T 23:43, 14 December 2005 (UTC)

title: Cookbook talk:Peanut Curry Sauce


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Systems Theory/Systems Approach to Instruction

What is a System
A system, S, is viewed as a whole made up of many parts or subsystems which are interconnected. To be considered as a system, S MUST have one or more objectives. In turn, each subsystem may itself be viewed as a system, leading to a hierarchy of systems (or subsystems). The system's parts are working together as a whole to accomplish the system's objective(s) by performing certain tasks. Ex. a computer. A system can also be defined as separate bodies coming together to form a system.

Keywords: system, subsystem, interconnection, objective

Systems Approach
The systems approach developed out of the 1950s and 1960s focus on language laboratories, teaching machines, programmed instruction, multimedia presentations and the use of the computer in instruction. Most systems approaches are similar to computer flow charts with steps that the designer moves through during the development of instruction. Rooted in the military and business world, the systems approach involved setting goals and objectives, analyzing resources, devising a plan of action and continuous evaluation/modification of the program. (Saettler, 1990)


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User:Ilya K

w:User:Ilya K

title: User:Ilya K


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World Stamp Catalogue/Stamp Inclusion policy

In this catalogue, the term "stamp" should be interpreted as any government-issued label that are designed and issued for use in payment of postal, revenue, penalty or related charges.

Several present day postal administrations have outsource their stamp issuing activities to agencies who design, print and distribute stamps. For examples, many countries in African regions outsource/contracting their postal to Stamperija for their postage stamps needs. This is important to consider that this is not government issued stamps and it is left up to contributor's discretion whether to include on this catalogue or not.

Other stamps were issued by governments in exile, pressure groups, political parties and organizations. These stamps are often, but not always, propaganda labels that were never actually used to pay for postal charges.

Finally, there are a subset of stamps known as "Cinderella Stamp", which are basically decorative stickers that resembles postage stamps but did not have values.

Stamp Inclusion policy


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Chess/Notating The Game

Notating chess games is important to any chess student, since it allows them to review their strategy and that of their opponent, to read of classic chess encounters, and follow how the game developed. Further, chess puzzles are often set in magazines, newspapers and online, and their solutions are notated; for an example, see The Times Chess.

Algebraic notation
A very common nomenclature for chess games is algebraic notation. There are several older systems of notation, but these are less common.

In algebraic notation, we use
 * R for a Rook;
 * N for a Knight;
 * B for a Bishop;
 * K for a King;
 * Q for a Queen;
 * no letter for a Pawn.

Sometimes a pictorial language-independent notation is used, in which a picture of a horse might represent a Knight, and so on.

Each square on a chess board is given by a coordinate, much like a map or a planar graph. The ranks (rows) are indexed with Arabic numerals 1 through 8, and the files (columns) are indexed with Latin letters “a” through “h.” A square’s coordinate is denoted as its file index followed by its rank index. For example, in the board below, black’s King is on the square d5.

If black moves his King to, say, d6, the move is notated as Kd6, i.e. the King has moved to square d6.

If more than one piece of the same type could have moved to the square to which the piece was moved, then the file of the piece prior to its move should come in between the piece's symbol and the coordinates of its destination (i.e., Qee7.) If necessary, the rank it was on may also be added, (i.e., Qe6e4.)

Moves in which a piece is captured, a King put in check, or checkmate have special notations.

 * If a piece is captured, a cross (x) is inserted just before the destination square. Thus, if the capture is done by a Pawn, the cross is preceded by the column the Pawn occupied prior to the capture.
 * If the King is put in check, the move's notation is followed by a plus sign (+).
 * If the King is put in checkmate, the move's notation is followed by a hash or double plus signs (#",++',) or the word "mate" or "checkmate."

Annotation shorthand
Annotation shorthand is not a notation system. Rather, it is a system of symbols for the player or annotator to add his descriptions or comments. A player or annotator notating a game might wish to highlight an excellent move, question a bad one, or indicate which player he thinks has the advantage.

 * If a move is followed by an exclamation mark (!), the player/annotator is surprised by the move's quality.
 * If a move is followed by a question mark (?), the player/annotator suspects the move may have been poor.
 * If a move is followed by an exclamation mark and then a question mark (!?), the move interests the player/annotator, though it may be sub-optimal.
 * If a move is followed by a question mark and then an exclamation mark (?!), the player/annotator fears that the move may be conclusive.

Repeating a symbol (e.g. !! or ??) adds emphasis.

Results are written as white's score followed by black's score. For example, 1–0 indicates that white won, and 0–1 indicates that black won. In the case of a draw, the result is ½–½.

There are some additional symbols for the player/annotator to note his thoughts on the game in general, rather than on any particular move.
 * An equals sign (=) indicates positional equality between the players.
 * A plus-minus sign (+/–) indicates that white is considered to have the advantage.
 * A minus-plus sign (–/+) indicates that black is considered to have the advantage.

Ambiguity
Sometimes algebraic notation can be ambiguous—that is, two pieces of the same designation can move to one square. For example, a player might be able to move either of his Rooks to the same square. In these cases, it is essential to specify which piece was moved.

The precise move is specified by designating the file (column) that the piece moved from, before the move's final co-ordinate. For example, Nd2 indicates that a Knight moved to d2, but Nbd2 indicates that the Knight that was in column b moved to d2. If a piece's file is not enough to precisely specify the move, then its rank is used instead. If neither is enough on its own, both are used.

Special moves
Some special moves are tricky to write in algebraic notation, and must have their own notation.

 * Castling King-side is written O-O.
 * Castling Queen-side is written O-O-O.
 * En Passant (or En Passe") (French for "In passing") capture is written as if the captured pawn only moved one square. The notation may be followed with e.p. or ep to clarify that the capture was done En Passant.
 * If a Pawn is promoted, the Pawn's initial move is written, followed by an equal sign and then the shorthand for the new piece; for instance, e8=Q. Any additional nomenclature or annotation is written after the shorthand for the new piece (such as c8=Q+ if a Pawn promoted to a Queen on c8 places the opposing King in check.)

Sample game in algebraic notation
If you have familiarized yourself with algebraic notation, consider this short sequence of moves. Try to follow the game by looking at the moves in algebraic notation, and the boards.

The game has begun, and is nearing the end. White is to move.

White decides to move his Bishop from d3 to c4, to check black's King. This is white's thirtieth move. So in algebraic notation, we write

 * 30. Bc4+

Since only one Bishop could move to c4, the Bishop's initial position was not specified. The + indicates the check.

White's Bishop is now, unfortunately, in the Queen's line of fire. Black decides to capture it. So for black's 30th move we write

 * 30... Qxc4

The x signifies that a piece has been captured. When black's move is written separately from white's, an ellipsis (...) is placed between the number and the move. The ellipsis indicates that white's move has been omitted.

The board now looks like this:

White is in trouble now, and decides to flee to f2. His move is

 * 31. Kf2

If black checks white's King, by moving his Queen to c2, his move is

 * 31... Qc2+

Descriptive Notation
An older form of notation you will run into quite frequently is Descriptive Notation. It is useful to know because older books use it.

In this form, instead of the files being a, b, c etc., they are Queen rook (QR), Queen Knight (QN), Queen Bishop (QB), Queen (Q), King (K), King Bishop (KB), King Knight (KN) and King Rook (KR). The ranks are labelled from your point of view so that the square e4 (in algebraic) is White's K4 and Black's K5.

To record the moving of a piece, you write the piece, then a dash, ("-") which means "moves", or "moves to" and to where it moves. 1. P-K4 means move a Pawn to the 4th rank in the King's file. N-Q-B3 means you move your Knight to the third rank in the Queen's Bishop file. For a capture, you specify the piece taking, and the piece to be taken. QRPxN means Pawn in the Queen Rook file takes Knight. Excessive notation is left out so that if there is only one way a Pawn could legally take a Knight, the move is recorded as PxN. Note that if a piece is specified to be on the King's or Queen's side of the board, that is the side it is on now, NOT the side it started out on. In rare occasions the move will still be ambiguous when, for example, both Knights can make a particular capture and both of them are on the same side. It would then be necessary to insert a "/" which means "on". For example: N/3XP (for the rank) or N/BXP (for the file).

In order to compare the two systems, we could look at the same game in both algebraic and descriptive notation in full (1, 3, 5) and abbreviated (2, 4, 6) notation.

 * 1.Note here that since only one Bishop can move to QN5, it is unnecessary to specify which Bishop moved to that square.
 * 2.Check is indicated by "ch", or "+", and "++" for the uncommon but not entirely rare double check, and "+mate" or "+++" for checkmate.

Coordinate Notation
A different type of notation uses only the squares that the pieces were on to denote movements; the dash "-" is inserted to denote "moves to". For example, to denote the earlier 7 moves, the following notes are shown:
 * 1) e2-e4 e7-e6
 * 2) d2-d4 d7-d5
 * 3) b1-c3 f8-b4
 * 4) f1-b5+ c8-d7
 * 5) b5xd7+ d8xd7
 * 6) g1-e2 d5xe4
 * 7) 0-0 or 0-0-0

ICCF numerical notation
A move is denoted by the file (1 to 8) and rank (1 to 8) of its starting square followed by its destination square (from 11 at the White Queen’s Rook square to 88 at the Black King’s Rook square). "1. e4" is denoted as "1. 5254" in ICCF notation. Unlike other notations, ICCF notation does not make apparent when castling, check, checkmate, and capture took place (castling King side is 5171 for white and 5878 for black). Pawn promotion necessitates a fifth number specifying the new piece (1=Queen, 2=Rook, 3=Bishop, 4=Knight). This notation is considered to be international in that there is no dependency on piece names or specific alphabets. However this notation still depends on Arabic numerals.

Manual de Ajedrez/Anotando un juego Scacchi/Annotazioni di gioco Catur/Mencatat permainan

title: Chess/Notating The Game


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Chess/Tactics

Guarding
When one of your pieces is placed so that it attacks a square occupied by another of your pieces, the former is said to be guarding the latter. When your opponent captures the guarded piece, you can recapture with the guarding piece. Note that if a guarding piece is pinned to your king (see below for a description of pins), it can only guard other pieces against capturing by the enemy king, but not from other enemy pieces, since it is unable to move or capture.

Batteries
Batteries are formed when two or more pieces work together. The most common kind of battery is the doubling of rooks on a file. Other batteries can be formed by rook-queen, bishop-queen, two knights or a bishop-pawn.

A triple battery can be constructed with the queen and both rooks. This is known as Alekhine's gun (diagram at right) and can be extremely dangerous. It is often advantageous to place the queen behind one or both rooks as it is a more valuable piece.

The Exchange
In almost any game, a player will have the opportunity to capture one of his opponent's pieces in exchange for sacrificing or losing one of his own pieces. This should however NOT be done for its own sake! Initiate an exchange only when it benefits you. Benefits can include, but are not limited to:

 * Material advantage - Exchanging one of your pieces for a more valuable opponent's piece (e.g. exchanging a bishop for your opponent's Queen).
 * Doubling pawns - Take when taking back means the doubling (or tripling) of your opponent's pawns on the same file.
 * Opening up the king's defenses - Take when taking back means moving a pawn that exposes the king.
 * Removing a defender - Take when the piece being taken is providing an essential service for the opponent.
 * Blunting an attack - When you are being attacked, often a well timed exchange will leave your opponent with too few pieces to keep up the attack.
 * Gaining space - In a cramped position, having more pieces can actually be a disadvantage because the pieces get in the way of each other. If your opponent has a space advantage, exchanging pieces can lessen the advantage and make the resultant position less confining.
 * Improving a material advantage - if you are ahead material, exchanging pieces will usually benefit you (note - pieces, NOT pawns). Similarly, if you have an extra pawn, trade pieces that may otherwise be used as a sacrifice to prevent pawn promotion.
 * Forcing checkmate - If you are able to force a checkmate by exchanging pieces, you should always take the exchange, even if the exchanges seem poor (e.g. sacrificing a Queen for a bishop). Note that a forced checkmate is one where there is no way for your opponent to prevent the checkmate.
 * Threatening checkmate - Sometimes, you can propose an exchange where you can force a checkmate if your opponent accepts the exchange. That is if your opponent captures your piece after you capture one of their pieces, you are then able to force a checkmate.
 * Preventing checkmate - If you are in a situation where the only way out of a checkmate is to exchange pieces, you must make the exchange.

Forks and Double Attacks
Sometimes a piece can be in position to attack two enemy pieces at once. This is called a fork or a double attack. All pieces can fork, even pawns, but knights have a reputation for making especially vicious forks because other pieces cannot block their way because the endangered pieces cannot defend by attacking it, unless they are another knight.

Forking with check
A knight fork that attacks the king from an unguarded square is very powerful. The opponent must then move his king to safety and the other piece in the fork has no chance of escape.

The Royal Fork
A royal fork is one involving both your opponent's king and queen. In the example shown here, white's knight on f7 has engaged black in a royal fork. Black will be down the exchange of a queen for a knight.

Forks do not always win material
If every time you saw a fork you played it, you would be making a mistake. You have to examine the different possibilities to escape the fork. In the queen fork on the right white has just played 1.Qd4+ forking the black king and rook. However black can play 1. ...Rg7 blocking the check and moving the rook to safety (although white could play 2.Qxg7, taking the rook, black could then play 2. ...Kxg7, taking the queen; white will then have lost the Exchange and will be unable to destroy Black's pawn majority, resulting in a forced win for Black, a queened pawn, and a king-queen checkmate.)

However 1.Qd4 is by no means a bad move. Perhaps White played 1.Qd4 in order to force black to play 1. ...Rg7 in which White can now play 2.Qd8+ (fork on king and pawn) Rg8 (forced) followed by 3.Qxa5 in which case White can push his a-pawn. Here White forked Black's king and rook not to win the rook but to later win a pawn by a fork, and pave the way for his a-pawn to become promoted to a queen. He might have also intended to play 3.Qf6+ Rg7 (forced) 4.Qxc6, eliminating Black's passed pawn.

Pinned pieces
A pinned piece is a piece that cannot move because it would expose an attack on an important piece by one of the opposing pieces, such that the capture of said piece would result in material gain by the opponent. A great tactic is to pin the opponent's pieces to his king; this is known as an absolute pin. For example, take a look at the board on the right. Black just moved his dark-squared bishop to b4. The white knight is now pinned and cannot move, because moving the knight would put himself in check. White's only way to stop the pin is to move his king. The pawn on e4 is no longer guarded by the knight, since the knight could not move to exchange.

The position diagrammed to the right shows the theme of attacking the pinned piece. White can look at this position and immediately take the rook and win an exchange. However this wouldn't even be the best move. If white did this then the material would be dead even; however, white has more pawn islands and it would be a very close game. Instead, white can play Ng5! The rook cannot move, and black has no way of effectively defending the rook a second time, therefore Black will eventually lose a rook. So, if you have pinned a piece, try to see if you can attack the piece again, and if a piece of yours is pinned, try to see if your opponent can attack it again. The moral of the story: if you see a good move, stop and look around for a better one.

In contrast to the absolute pin, a relative pin occurs when one player's piece is pinned to one of lesser value than the king, such as a queen or rook. If the benefit of moving the pinned piece outweighs the loss of material occasioned by the capture of the exposed piece (for example, if a forced mate may be achieved), then the pin can be disregarded and the pinned piece moved.

Skewers
A skewer is similar to a pin, but it is in a sense more powerful. The difference between a pin and skewer is the location of the more important piece. In a pin the lesser piece blocks the attack on the more important one, in a skewer the more important piece is attacked first and when it moves it exposes the lesser piece behind it to be hit. Black has, in a blunderous moment, placed his king on d7 in front of his queen on d8. White may now triumphantly slide either rook to d1, skewering Black's king and queen. Since Black cannot block the check, the king has to move, exposing the black queen to the attack of the white rook.

Discoveries
A discovery is an attack on an enemy piece which is unveiled by moving one of your pieces. The power of discoveries is that two targets can be attacked simultaneously. If combined with a check they can be lethal.

Note that White's 1.Nd7+ was a double check, a type of discovered check where the piece moving also gives check. Such checks are very powerful, since the king is forced to move (both checks cannot be blocked at the same time). They are also often lethal, as in the above game.

A simpler example of a discovered checkmate is shown below.

Removing the defender
By first capturing, threatening, or pinning a piece that guards another, you should be able to capture the other piece for free. You can also remove the defender of a position. By using tactics you might be able to force a checkmate!

Sacrifices
A sacrifice is an exchange of a piece for a non material advantage:

In the first diagram, White just moved '''1. Kh1''' to get out of check.

Black sacrifices his queen with 1...Qg1+ for a winning positional advantage - White is in check and can not take with his king because the knight guards the queen.

2. Rxg1 - forced - this smothers the king - he cannot move because his own pieces are on every square he could go to - any check on an unguarded square now is mate.

2...Nf2# Checkmate. This queen's sacrifice was an example of a smothered mate (in which a knight delivers a checkmate that is caused by the king's inability to move anywhere). In fact, this is a special kind of smothered mate, called Philidor's Legacy.

Zwischenzugs
A Zwischenzug (pronounced "TSVISH-en-tsoog",) or "in-between move," is one that is made unexpectedly in the midst of a sequence of moves. But not just any series of moves, one in which the player falling for the Zwischenzug feels the sequence is forced, while his opponent demonstrates to him that it certainly isn't! Most commonly these fall in between trades where a recapture seems to be the only proper means of play.

Such in-between moves often have a surprising and pleasing effect of increasing the potency of a combination beyond the opponent's expectations.

In Borisenkov-Mezenev (shown in the diagram to the right), black played 1... f2, threatening to queen, which White countered with '''2. Rg8, intending 3. Rf8+, and 4. Rxf1'''. But White resigned after the Zwischenzug 2... Bb1! which allows Black to queen (3. Kxb1 f1=Q+ or 3. Rf8+ Bf5).

Scacchi/Tattica

title: Chess/Tactics


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Chess/Strategy

Strategy Basics
You may choose different strategies depending on what type of opponent you are playing, and what kind of player you are. Strategy starts with the opening, and continues through the middlegame, and on to the endgame.

Games are considered open if the exchange of pieces have opened up files or diagonals, and closed if they have not. These games are called open or closed because there is more mobility for one’s pieces in open games, and because this category usually determines the complexity of the game. Specifically, recognition of open versus closed games is important because closed games are more conducive to Knights, whereas open games see more involvement with longer range pieces such as Bishops, Queens, and Rooks.

Strategic Openings: If you choose to play a long-range, theoretical sort of game, you may want to choose a complex opening such as the Queen’s Gambit, the Ruy Lopez, or the English. In these types of games, especially when you are playing the closed variations, you are likely to venture into close positions where positional maneuvering predominates over tactical shots. From there, you can focus on strategic elements like controlling files, pawn structure, and other long range development considerations.

Tactical Openings: If you are more interested in sharpening your tactical play and focusing on combinations, you may choose a more tactical opening. Some of these openings include the Sicilian Defence (especially the Dragon and the old main line of the Najdorf), the Grünfeld Defence, and the older variations of the Two Knights' Defence.

By initiating exchanges you can always simplify the game, and it will become more computational. If you don’t want that to happen, you have to be very guarded and conservative.

You should always be thinking about how many squares a piece controls (i.e. can attack), and which squares are controlled. In the beginning you should aim to control the center of the board. As the game progresses you may want to attack one flank, especially if the King has castled onto that side.

Material advantage
Having more valuable pieces on the board than your opponent means you have a material advantage. If your position otherwise is equal, you will be more likely to win. Since not all pieces are equal, many people use the following point system to estimate which player has a greater material advantage:

 * Pawn = 1
 * Knight = 3
 * Bishop = 3
 * Rook = 5
 * Queen = 9
 * King = infinite (3.5 as an attack/defense strength during end game)

However, a slightly more accurate system is as follows:

 * Pawn = 1
 * Knight = 3½
 * Bishop = 3½
 * Rook = 5
 * Queen = 9
 * King = infinite

These values can only be used as guidelines for the relative value of the pieces; a piece's value in a particular chess position must be treated on a case-by-case basis.

Queenside vs Kingside
When calculating the value of a position, dividing the board in Queenside and Kingside, it will be seen that it matters that the king is considered to be worth 3.5 points. The calculation of forces on either side will determine the stronger side. This side usually can become the attacking one, all other things considered.

The pieces' relative value changes over time
The value of the pieces changes as the game progresses, because there is less material on the board to get in the way of some pieces. Rooks usually become more powerful because there are fewer pawns in the way, and a rook has the opportunity to control more squares. Bishops can travel great distances if unobstructed, while knights have a more local presence. So, knights shine when the board is cluttered in a closed game because they can "jump" over pieces whereas bishops are generally stronger in open games where they have the run of the board.

The value of the King
Assigning a point value to the King for the sake of deciding to trade the King for other pieces doesn’t make sense, since capturing the King is the object of the entire game! Therefore it is customary to either exclude the King from the point value scale, or assign it an infinite value. However, keep in mind that the King has an attacking and defense capability as any other piece.

The King attack and defense value changes dramatically as the game progresses. During the opening and middle game the King is a piece that needs to be protected against checkmate at all cost. Its usefulness as an attacking or defending piece is thus limited. However its strength as an attacking piece becomes greater in the endgame. In this phase of the game it is generally reckoned to be stronger than a knight or bishop but weaker than a rook. Therefore giving the King an attack or defense point value of 3.5 during the endgame makes sense.

Knight vs Bishop
Based on the point value scale above the value of the knight and bishop appears to be the same. Alternative scales have tried to assign the knight and the bishop slightly different values, usually preferring the bishop over the knight. But since the relative value of the knight and bishop is strongly related to the position, such minor differentiation provide little overall guidance.

Knights are more powerful if they have a safe outpost in enemy territory - a knight on the 6th rank that cannot be attacked by opposing pawns can be as powerful as a rook in the right circumstances. This type of knight, if guarded by a pawn, is called “a home away from home”.

A bishop never leaves its own color, so if one of the bishops is captured, half the board is now out of reach of a bishop. So trading one bishop for a knight tends to favor the person losing the knight, who is left with two bishops. However, trading the second bishop isn't quite so hurtful. So trading a bishop for a bishop where one side has only 1 bishop to begin with helps the side with fewer bishops.

Knights cannot cover both sides of the board at the same time, while a bishop can, so in an endgame where there are pawns on both sides of the board, the bishop is stronger.

Bishops cannot attack pawns that are on the opposite color, while a knight can. Furthermore, in a game where there is a short pawn chain, a knight can stand at the head of the chain and attack the pawn supporting it, so a knight is often more effective attacking pawns as long as they are limited to one side of the board.

Finally, it is possible to force checkmate with two bishops and king against a lone king, but not with two knights and king versus lone king.

It is important to keep in mind what sorts of positions will benefit the pieces that you have. For example if you have 2 knights and no bishops and your opponent has 2 bishops and no knights then it would be good for you to keep the center cluttered with pawns by avoiding pawn exchanges. If you do this then your opponent's bishops will have hampered mobility whereas your knights can hop over the pawns. Also if you have the bishops and your opponent has knights then you should play to keep the center clear so your bishops can have more mobility. Also, this idea can help you decide on whether or not to trade a bishop for a knight or vice versa.

More pieces are usually better
Usually having more pieces is more valuable when the point value is roughly equal for both players—two bishops beat a rook, two rooks beat a queen—but this is conditioned on proper co-ordination between the pieces. It may be worthwhile to sacrifice two pieces for a rook if this results in long-term damage to the enemy's piece co-ordination. Usually this means tying down the extra pieces to the defense of weak pawns, so that they cannot cooperate in attacking friendly pawns.

Compensation
Material values only matter in the context of position. Compensation is a term used in chess to describe the trade off between material and positional advantage. A strong position can make up for a material deficiency. For example if your opponent has all their pawns on white squares, a black bishop is worth more than a white bishop.

Typically having compensation for a piece means that an attack against the enemy's king or strong points cannot be repelled or may only be repelled by the enemy returning the material he is up. Often compensation can refer to having the initiative or in trapping the opponent's king in a vulnerable position. A pawn majority on one wing or a passed pawn can also sometimes be considered compensation for a minor piece. Generally the player who is down on material has to act quickly and avoid exchanging pieces to prevent the enemy from making his material advantage count.

Pawn Strategy and Pawn Chains
In the end game, pawns gain strength as they advance because they pose the threat of promotion, so a pawn on the 6th or 7th rank is worth significantly more than a pawn on the second rank - often as much as a piece. However, in the opening and middlegame, an advanced pawn is less likely to promote and more likely to be in need of being defended. It is also unable to defend the center and often leaves "holes" in your territory that can serve as outposts for your opponent's pieces. An overadvanced pawn is then often a liability.

In the opening and middle game, pawns in the center of the board block paths and support outposts. So they tend to be more valuable than end pawns. However, in the end game, a wing pawn is usually the hardest to get to and block or capture and is therefore more likely to queen. So in the endgame, the edge pawns are often more valuable than the middle pawns (Note: this is not necessarily true in some basic pawn and king endings, where a pawn on the edge leads to only drawing options).

A passed pawn has only pieces stopping it from queening, so it is considered more valuable - especially if it is protected by another pawn.

Tempo
Tempo is the effective number of moves required to reach the position on the board. Moving a piece twice to reach a position it could have reached in one results in a net loss of one tempo - moving a piece back to its starting place usually results in a loss of all its tempo - unless other pieces moved that could not have moved otherwise. Also the capture of a piece means all of the tempo it gained is lost as well.

Essentially, tempo is one way of showing how many effective moves you have made. So the gain of a tempo is basically like getting a move for free. Three tempi is usually considered equivalent to a pawn in terms of advantage.

Example:

In the position above there have been 2 tempi played on each side, play continues with:

'''3. cxd5 Nxd5 4. e4 Nf6'''

Now white still has 2 Tempi (one for d4 and 1 for e4) while black only has 1. The captured pieces lost the tempo they had gained in moving and the knight lost the tempo it had when it captured.

For argument's sake, lets assume play went as follows:

'''5. e5 Nd5 6. Bc4 Nb6 7. Qd3 Na4 8. Nc3 Nxc3 9. Qxc3 e6'''

Now black still has only 1 tempo (e6) while white has 6 (2 queen moves, 3 pawn moves and a bishop move). This has let white develop 2 pieces, control the center and give black a cramped position. Also, while both sides can castle kingside in the same number of moves, White can connect his rooks (position them so there is nothing between them on the back rank) 2 moves sooner than black. Chances are, white will complete development and launch an attack before black is able to. This means white will have an advantage when the middlegame is reached.

Active and passive pieces
An active piece is one that has the potential to make a threat. A passive one is usually relegated to defending a piece.

In this example, white's bishop on g5 is considered active, while black's bishop on e7 is considered passive.

Piece activity depends on whether it can move and attack. A piece can be rendered passive if it is stuck protecting another piece or if it is restricted from being able to get into play by its own pawns.

Good vs. Bad Bishops
As noted above, a bishop can only travel on squares of one color. This leads to a situation wherein one bishop may be effectively blocked out of the game by the pawn structure. In general it is better to have your pawns on the opposite colored squares to your bishop. For example, if you as black have pawns on e6 and d5, your queen's bishop is likely to be a "bad bishop." It is bad because it is hard to do anything constructive with it; developing it to g4 is impossible and "fianchettoing" it via b7 is ineffective since your pawn on d5 blocks any influence it may have over the centre. When one has a bad bishop there are two methods to improve the game: exchanging the offender and freeing up the game. In general it is profitable to try to exchange your bad bishop for an opponent's bishop or knight, as your bad bishop has little value. However, it is important to bear in mind that in the end game having two bishops is considerably stronger than have two knights or a bishop and a knight. Therefore you should always be wary of exchanging bishop for knight in situations where an endgame is likely. The other method to rid yourself of this weakness is by freeing up the game through making pawn moves.

Overloaded pieces
Overloaded pieces are pieces which defend too many other pieces and therefore cannot be considered to defend all of them at once. For example, a rook can defend up to 4 pieces, but if one is taken, and the rook takes the offending piece, 2 of the other pieces are undefended.

Initiative
The player with the initiative is the player who is making the threats to which the other person must respond. Having the initiative is advantageous because it forces your opponent to place his pieces in essentially defensive formations. A piece that is defending a square generally has less mobility (freedom of movement) than a piece attacking the same square.

Having the first move, it is generally white who has the initiative in the early part of the game. Therefore trying to maintain the initiative would be prudent strategy.

Zugzwang
A Zugzwang situation occurs when any move a player makes will weaken his/her position, but he/she is compelled to move in accordance with the rules. An example of zugzwang is as follows:

White moves and wins.

1. a4 : White moves the a-pawn, blocking the black a-pawn to move forward. Black has only one legal move; moving the black king out of the way of the d-pawn's path.

1. ... Ke7 : The black king is forced to move away from his current position where he blocks the d-pawn's path to promotion, because he now has no other legal move to make. Since this move is not desired by Black, as he would rather keep his king on the d8 square where it stands to continue blocking the white d-pawn, Black is "in zugzwang".

2. Kc7 : White's king continue to protect the pawn on d7 from capture, and blocks black's king to move back to it desired location of d8.

2. ... Ke6 : Black can make other legal moves with the black king, but they will yield the same result. Even if Black must move the king, this is not an example of zugzwang. Keeping the king at e7 would not yield a better result for Black, since the d8 promotion square is protected by the white king.

3. d8=Q : White gains a queen and wins the game easily.

Alternatively, white can force a win by moving the king first: 1. Kd6 a4 2. Kc6(Ke6) Ke7(Kc7) 3. Kc7(Ke7) with 4. d8=Q to follow

Exercise: From the same initial position but with black to move first, show that Black can force a draw by using zugzwang.

Solution: 1. ... a4 2. Kb5 Kxd7 (White's move is Zugzwang.) 3. Kxa4 Kc7 4. Kb5 Kb7 5. a4 Ka7 6. a5 Ka8 7. Kb6 Kb8 8. a6 Ka8 9. a7 	(Draw by stalemate.)

Combining attack with defense
A winning strategy in Chess often involves balancing several considerations against each other. Moves that maximize immediate material gain might expose a vulnerability or yield a difficult position as the game progresses. Similarly, material sacrifices for position may be disadvantageous if they cannot be parlayed into an effective attack. Thus, a key consideration should be balancing attack with defense. A profitable move would be one that both furthers your attack and solidifies your defense.

 * Yasser Seirawan in his Pro Mentor DVD.

Manual de Ajedrez/Estrategia Scacchi/Strategie Xadrez/Estratégia

title: Chess/Strategy


text:
Chess/Basic Openings

The following is an overview of the aims of an opening and some standard openings that you can try in your games. All of them are playable and should lead to reasonable games with best play.

Aims of an opening
Before looking at some of the more common openings played today it is important to consider what you are trying to achieve in the opening of a chess game.

In some cases, one player will sacrifice a pawn, or in some cases even more, to accomplish the goals listed below. Such an opening is called a gambit.

Development

You should attempt to move your pieces away from their starting positions to squares in which they can participate more fully in the game. Obviously a Knight at c3 is more effective both defensively and aggressively than a knight on b1. Avoid moving pieces more than once in the opening as this allows your opponent time to develop another piece while you are wasting time. Also avoid moving your queen in the opening, it can too easily be chased around the board by other pieces which aids your opponent's development while wasting moves for you.

Control the Centre

The squares in the centre of the board are critical for two reasons. The first is that pieces in the centre are able to move to more squares than pieces on the edges. (Note a knight on a3 can move to only 4 squares, whereas a knight on c3 can move to 8.) Secondly, if you control the centre it is easier to move pieces from Kingside to Queenside quickly.

One of the great truths in chess is that attacks along one wing are destined to fail if the centre is not sufficiently controlled. This is because the defender with a strong centre will generally be able to muster enough defence on that side and at the same time mount a counterattack in the centre and/or on the other wing. So if you plan on mounting an attack make sure you control the centre.

Traditionally it was thought that the ideal situation is one where you have a pawn majority in the centre, especially with pawns on d4 and e4 (for white). However it has been shown that an equally valid strategy is to control the centre with pieces and make minimal pawn moves. The thinking is that central pawn moves often lead to permanent positions and can block attacks. "Fianchettoing" a bishop by moving it to b2 or g2 after b3 or g3 allows the bishop to keep a watchful eye on the centre without fixing a pawn in the centre.

Castle

A King in the centre of the board is open to attack. It is generally a good idea to castle your king so as to be able to defend it more easily. Some players will sacrifice material in order to prevent the enemy king from castling and to attack it ferociously due to its vulnerability. Castling also has the added benefit of bringing the rooks together on the first rank so that they are able to combine in defence and attack. Once your pieces are developed, king is safely castled, and your rooks are combined, the opening is over.

Protect the King

It is not always necessary although highly advisable to protect the king through castling. That being said, there are other ways to go about protecting the king than castling although they are less efficient and will often result in pins.

Ruy Lopez (aka Spanish Opening)
1.e4 e5 2.Nf3 Nc6 3.Bb5 the main line continues 3...a6 4.Ba4 Nf6 5.0-0

The move 3...a6 works because if white plays 4.Bxc6 dxc6 5.Nxe5, Black can regain the pawn with 5...Qd4 forking the e4 pawn and the knight.

Italian Game
1.e4 e5 2.Nf3 Nc6 3.Bc4

There are two key replies: 3...Bc5, known as the Giuoco Piano (Italian for Quiet Game), and 3...Nf6 headed to a much more involved opening called the Two Knights Defence.

School children in local clubs often drift into weaker variants of the Giuoco Piano, mostly out of insufficient knowledge. A few scholastic trainers have even suggested avoiding the opening, as there are fewer crisp strategic concepts compared to many other openings.

Russian Game (aka Petrov Defence)
1.e4 e5 2.Nf3 Nf6

The Petrov Defence may look like a counter-attack, and very early on this was supposed to be the idea. However, it soon became apparent that the symmetrical nature of the opening produced defensive positions. If White takes the pawn, Black should avoid taking it back because of 4. Qe2 Nd6?? 5.Nc6+ which wins the black queen. The main line goes 3. Nxe5 d6 4. Nf3 Nxe4. It is considered quite solid, and is a key defensive opening against the dangerous first move 1. e4. There are a few gambits which White can try to shift the style of the opening. The Cochrane gambit is perhaps the most dangerous. It involves a Knight sacrifice on f7. Currently not considered objectively sound, its use is psychological: White dares the opponent to spend twenty moves defending against an attack, and this pressure may cause the Black player to finally fall victim to a tactical shot.

Philidor Defence
1.e4 e5 2.Nf3 d6

If Black wants to defend the threatened pawn with a pawn, this is the way to do it (playing 2...f6? is plain bad, as 3. Nxe5 fxe5 4. Qh5+ is winning for White). It gives Black a solid but somewhat cramped position. The f8 bishop is hemmed in and will be relegated to a defensive role. The Black knight retains the option of going to d7 leaving the c-pawn mobile, but it is not without reason that 2...Nc6 is much more common than 2...d6.

Danish Gambit
1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2

This gambit gives White quick development and control of the center at the cost of two pawns initially. However, current opinion reports that to properly fend off the attacking waves, at least one and sometimes both pawns must be returned. This involves the liberating pawn push ...d5 by Black. Even so, inventive attacking players can still use the resulting open lines to play a complex game.

Sicilian Defence
1.e4 c5

Play can continue

2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 (2...d6 and 2...e6 are also common, and usually also met by 3.d4)

The Sicilian is the most common and best-scoring response to 1.e4, as it balances the white advantage with flank play. It discourages White from occupying the centre with 2.d4. After 2...cxd4 White must either take the pawn back with the queen (and move it again after 3.Qxd4 Nc6) or sacrifice the pawn, usually with 3.c3.

One problem with the Sicilian is that there is a vast amount of theory written on it, and in a sharp opening like this, you can wind up in trouble if you don't know it.

French Defence
1.e4 e6 2.d4 d5

White has three essential continuations: 3.Nc3 "Winawer Variation" 3.Nd2 "Tarrasch Variation" 3.e5 "Advance Variation".

A fourth alternative, the "Exchange Variation" is 3. exd5, but this actually frees Black's game from all of the traditional cramping problems of the French Defence. It is mainly used by White players who forgo all attempts at a theoretical battle, hoping to play on "general principles".

The French Defence is considered one of the strongest black responses to the White opening move 1.e4. Among world class grandmasters, it currently trails the Sicilian 1. e4 c5 and the symmetrical 1.e4 e5 in popularity.

Pirc Defence
1.e4 d6, usually followed by 2.d4 Nf6 3.Nc3 g6

This opening bears considerable similarities to another one called the King's Indian, which begins 1.(e4 d6) d4 Nf6 2. c4 g6 3. Nc3 Bg7. However, subtle but long range strategic differences exist between the two. In the Pirc, White's c-file pawn is still at home, and not committed to the c4 square. This means that overall, White has better control of the d4 square. The pawn move c2-c4 has been replaced by a developing piece move N-c3, and this "faster" development tends to encourage White towards central or kingside attacks compared with the queenside play classically associated with the King's Indian defence.

Modern Defence
1.e4 g6, usually followed by 2.d4 Bg7

This move order is often used to "back into" a Pirc defence, while avoiding specific move order issues. However, an entirely different range of strategy is possible based upon ...c6 and ...d5.

Alekhine's Defence
1.e4 Nf6, usually followed by 2.e5 Nd5 3.d4 d6

This looks like a rather alarming opening for Black to play. Black lets White chase the knight around the board and use that time to build up the pawn centre. Black's plan is to show that White has expanded too quickly, and will find the pawn centre vulnerable. The disadvantage to this opening is that if White succeeds in maintaining it, White will have a serious and suffocating advantage in space.

Scandinavian Defence
1.e4 d5, usually followed by  2.exd5 Qxd5 3.Nc3 Qa5

Playing d7-d5 is the main idea behind most of the semi-open games for black. Here it is played immediately for the price of an extra move with the queen after 3.Nc3.

Long disparaged as the epitome of weak play "because moving the queen early wastes time", it was resurrected in the 1990s with a pawn move c7-c6, allowing the queen to retreat from a5 to c7 when necessary. Now it is considered an attempt to reduce White's central pressure, and is popular among club players because White suddenly has to demonstrate some sophistication.

1.e4 d5 2.exd5 Qxd5 3.Nc3 Qa5 4.d4 Nf6 5.Nf3 Bg4 6.h3 - possible continuation...

This is a general continuation of the Scandinavian Defense. White developing its pieces towards the center by 4.d4 and 5.Nf3 placing the Knight on the natural f3 square. Meantime black develops also in a simple way 4...Nf6 and 5...Bg4 creating a pin for the white Knight. There is another pin for c3 Knight - created by the d4 pawn push. Now white has to eliminate the pins - in order to make the Knights free to move. White can do it by 6.h3 move or 6.Be2 - simple relieve for the Bishop pin. After 6.h3 black Bishop can retreat by 6...Bh5 - maintaining the pin or can capture the white Knight 6... Bxf3.

1.e4 d5 2.exd5 Qxd5 3.Nc3 Qa5 4.d4 Nf6 5.Nf3 Bg4 6.Be2 ?! - thematic continuation...not the best one...

Most of the club players - or "players in the parks" or casual internet players without any deep opening knowledge are taking this 6.Be2?! move as a smooth continuation to relieve from the Bishop pin.

The normal development of the pieces continues 6...Nc6 7.0-0 0-0-0 8.Be3 ...

Queen's Gambit
'''1.d4 d5 2. c4'''

2...e6 3.Nc3 Nf6 4.Bg5 Be7 leads to Queen's Gambit Declined variations. A special characteristic among the declined games has the Tarrasch-Defence 3... c5, mostly followed by 4.Nf3 Nc6 5.cxd5 exd5.

2...c6 (usually followed by 3.Nf3 Nf6 4.Nc3 dxc4) leads to the "Slav Defence".

This is one of the opening "families" with interchangeable moves. It is quite possible to play both ...e6 and ...c6 (known as the Semi-Slav), and there are large numbers of interchangeable points called transpositions.

2...dxc4 is the "Queen's Gambit Accepted".

Black has gained a pawn but Black cannot keep it. If White wants it back White can play e2-e3 at some point, threatening the pawn with the bishop and if Black tries to defend it with ...b5 Black will find the queenside severely weakened (and the pawn should fall anyway). Nonetheless, this is playable for Black as well, instead of trying to keep the pawn, it is best to develop quickly and strike back at the White centre.

King's Indian Defence
'''1.d4 Nf6 2. c4 g6'''

'''3.Nc3 Bg7 4. e4 d6'''

Popularised after World War II, the King's Indian Defence involves opposite sides strategies in a race between Black's mating attack vs. White's methodical attempts to unravel Black's Queenside.

At World Class level, there is some concern that Black's concept is very committal, leading Former Champion Garry Kasparov to discontinue his use of the opening shortly before he retired from the game. At any level below that, it is still very popular due to the deep developmental work by Fischer and Kasparov.

Grünfeld Defence
1.d4 Nf6 2.c4 g6

3.Nc3 d5

Looks a bit like a cross between the Queen's Gambit and the King's Indian Defence, but this opening is played differently from both of them. Black gives White an early opportunity to grab control of the centre with 4.cxd5 Nxd5 5.e4. Black will need to launch a counterattack against that centre, perhaps with ...c5 to stop White from getting the upper hand. If Black succeeds, the White centre may indeed be very vulnerable, if Black fails, the centre will be very dominating.

Nimzo-Indian Defence
1.d4 Nf6 2.c4 e6

3.Nc3 Bb4

After 3.Nc3, White threatens to take control over the centre by playing 4.e4. The Nimzo-Indian, named after the hypermodern player Aron Nimzowitch, is one of the two main ways of preventing this (the other way is the direct 3...d5 which leads to the Queen's Gambit Declined). Black puts a bishop where it pins the White knight, and often intends to trade it off, surrendering the bishop pair but inflicting White with doubled pawns if needed to recapture with the b-pawn. White can avoid these doubled pawns by playing the queen to c2, but this costs time. On the other hand, Black has not staked out a big claim of the centre yet, and White can get a real space advantage if Black is careless.

Queen's Indian Defence
1.d4 Nf6 2.c4 e6

3.Nf3 b6

Strategically, this opening is similar to the Nimzo-Indian. White has played 3.Nf3 rather than 3.Nc3 so he is not threatening to grab the center with 4.e4 just yet. Playing the Nimzo-like 3...Bb4+ anyway is possible (and called the Bogo-Indian) and tends to lead to rather quiet play. More usual is 3...b6 which opens up for the bishop to go to b7 where it will continue the clamp-down on the e4-square, or to a6 where it will put pressure on White's pawn on c4.

Modern Benoni
1.d4 Nf6 2.c4 c5

3.d5 e6

Benko Gambit
1.d4 Nf6 2.c4 c5

3.d5 b5

English Opening
1.c4

Black's most common responses are:

1...e5, a reversed Sicilian Defence

1...c5

1...Nf6

1...e6 (preparing 2...d5)

and 1...c6 (preparing 2...d5)

Réti Opening
1.Nf3 d5 2.c4

Benko Opening
This opening threatens to fianchetto the bishop on f1 to g2, threatening a rook capture, or h3, threatening a bishop exchange, either of which would also threaten a Black pawn center. However, this opening is rather passive and is relatively easy to parry.

King's Indian Attack
1.Nf3 d5 2.g3

Barnes Opening
This can end almost as quickly as it begins, with an extremely fast checkmate by Black (called fool's mate.)

The Barnes Opening goes like this: 1.f3 e5.

It can be continued as the Fool's Mate: '''2.g4?? Qh4#'''. Fortunately for White, the fool's mate is extremely rare, even among novices, because the Barnes Opening is passive and has no advantage over 1.f4, and because it is very easy for even a novice to see that the continuation of the Barnes Opening gives Black an immediate mate opportunity.

Scacchi/Aperture di base Shakkiaapinen/Avausteorian alkeet

title: Chess/Basic Openings


text:
Chess/The Endgame

The Endgame is the last stage of chess, and arguably the most important. Even if you succeed in the opening and middle stages of the game, not knowing the skills to turn the resulting endgame into a checkmate can cost you many wins, turning many otherwise easily won positions into draws or even losses. For this reason, we recommend devoting a good portion of your study to endgames.

If you're still beginning your chess studies, the Basic Checkmates section should be enough to cover the simplest scenarios appropriate for your level. More complex situations are covered in the second part of this manual, suitable for those who already have a decent grasp of the easy checkmates.

Basic Checkmates
These include positions that have no pawns. When one side is ahead in material and has pawns, the easiest winning plan is typically to queen one or more pawns and use them to checkmate.

The situations where one has a king and queen, king and two rooks, or king and rook versus a lone king occur very often and it is essential to know how checkmate is achieved in such cases. The other cases, with minor pieces (bishops and knights) are more rare and more difficult to perform, but nonetheless are covered here for completeness.

 * King and Queen vs. King
 * King and Two Major Pieces vs. King
 * King and Rook vs. King
 * Minor Pieces
 * Pawn Endings

More Advanced Endgames
These are situations that occur less commonly in games, but are still very important. Most intermediate to advanced players are expected to have at least a basic understanding of how these endings work.
 * Endings with Multiple Major Pieces
 * Rook and Minor Piece Endings
 * Rook and Pawn Endings
 * Endings with 3+ Minor Pieces
 * Other Endgames

 * Endgame Studies and Puzzles

title: Chess/The Endgame