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User talk:Twisp

It's never too late for a Welcome message
Welcome, Twisp!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally. Webaware talk 10:31, 7 April 2008 (UTC)

Your account will be renamed
Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called Twisp. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Twisp~enwikibooks that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.

Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.

Sorry for the inconvenience.

Yours, Keegan Peterzell Community Liaison, Wikimedia Foundation 23:49, 17 March 2015 (UTC)

title: User talk:Twisp


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Talk:Old English/Verbs

Untitled
hı ı have questıon why there ıs deferent between verbs for example why teh form of do change to does why escan you answer

The present participle
Everything said under the paragraph regarding "The present participle", should be instead referred to as "Gerund", ffs.

Lufast
In Wiktionary the 2s indicative is lufast not lufiast. (See the Wiktionary lufian conjugation here.) Which is correct? Lufast would be consistent with the simple forms (without doubled consonant, without i) occurring in 2s & 3s indicative, 2s imperative, and all of the past tense. Wodorabe (discuss • contribs) 14:00, 13 February 2016 (UTC)

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

title: Talk:Old English/Verbs


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A-level Physics (Advancing Physics)/Young's Slits/Worked Solutions

'''1. A 2-slit experiment is set up in which the slits are 0.03 m apart. A bright fringe is observed at an angle 10° from the normal. What sort of electromagnetic radiation was being used?'''

$$\lambda = d\sin{\theta} = 0.03 \times \sin{10} \approx 5.21 \times 10^{-3}\mbox{ m}$$

So, microwaves were being used.

'''2. Light, with a wavelength of 500 nm, is shone through 2 slits, which are 0.05 m apart. What are the angles to the normal of the first three dark fringes?'''

$$n\lambda = 2d \sin{\theta}\,$$

$$n \times 500 \times 10^{-9} = 2 \times 0.05 \times \sin{\theta}$$, where n is an odd integer.

$$\theta = \arcsin{\frac{n \times 500 \times 10^{-9}}{0.05 \times 2}} = \arcsin{(n \times 500 \times 10^{-8})}$$

Then, substitute in n = 1,3 and 5 to gain corresponding values of θ:

'''3. Some X-rays, with wavelength 1 nm, are shone through a diffraction grating in which the slits are 50 μm apart. A screen is placed 1.5 m from the grating. How far are the first three light fringes from the point at which the normal intercepts the screen?'''

$$n \times 10^{-9} = \frac{50 \times 10^{-6} \times x}{1.5} \approx 33.3 \times 10^{-6} \times x$$, where n is an integer.

$$x = \frac{n \times 10^{-9}}{33.3 \times 10^{-6}} = 30 \times 10^{-6} \times n$$

Then, substitute in n = 1,2 and 3 to gain corresponding values of x:


text: User talk:68.174.27.152

title: User talk:68.174.27.152


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A-level Physics (Advancing Physics)/Forces and Power

Forces
Forces are vectors. When solving problems involving forces, it is best to think of them as lots of people pulling ropes attached to an object. The forces are all pulling in different directions, with different magnitudes, but the effect is in only one direction, with only one magnitude. So, you have to add the forces up as vectors.

Forces cause things to happen. They cause an object to accelerate in the same direction as the force. In other words, forces cause objects to move in a direction closer to the direction they are pulling in. If the object is already moving, then they will not cause it to move in the direction of the force, as forces do not create velocities: they create accelerations.

If a force is acting on an object, it seems logical that the object will not accelerate as much as a result of the force if it has a lower mass. This gives rise to the equation:

$$F = ma\,$$,

where F = force applied (in Newtons, denoted N), m = mass (in kg) and a = acceleration (in ms−2). If we rearrange the equation, it makes more sense:

$$a = \frac{F}{m}$$

In other words, the acceleration in a given direction as the result of a force is equal to the force applied per. unit mass in that direction.

Work Done
You should already know how to calculate some types of energy, for example:

$$\mbox{Kinetic Energy } = \frac{mv^2}{2}$$

$$\mbox{Gravitational Potential Energy } = mgh\,$$

The amount of energy converted by a force is equal to the work done, which is equal (as you already know) to the force multiplied by the distance the object it is acting on moves:

$$\mbox{Work Done } = \Delta E = F\Delta s\,$$

When answering questions about work done, you may be given a force acting in a direction other than that of the displacement. In this case, you will have to find the displacement in the direction of the force, as shown in the section on Vectors.

Power
Power is the rate of change of energy. It is the amount of energy converted per. unit time, and is measured in Js−1:

$$P = \frac{\Delta E}{t}$$,

where E = energy (in J) and t = time (in s). Since ΔE = work done, power is the rate at which work is done. Since:

$$\Delta E = F\Delta s\,$$

$$\frac{\Delta E}{t} = F\frac{\Delta s}{t}$$

$$P = Fv\,$$,

where P = power (in Watts, denoted W), F = force and v = velocity.

Gravity
Gravity is something of a special case. The acceleration due to gravity is denoted g, and is equal to 9.81359ms−2. It is uniform over small distances from the Earth. The force due to gravity is equal to mg, since F = ma. Therefore:

$$a = \frac{F}{m} = \frac{mg}{m} = g$$

Therefore, when things are dropped, they all fall at the same acceleration, regardless of mass. Also, the acceleration due to gravity (in ms−2) is equal to the gravitational field strength (in Nkg−1).

Questions
1. I hit a ball of mass 5g with a cue on a billiards table with a force of 20N. If friction opposes me with a force of 14.2N, what is the resultant acceleration of the ball away from the cue?

2. A 10g ball rolls down a 1.2m high slope, and leaves it with a velocity of 4ms−1. How much work is done by friction?

3. An electric train is powered on a 30kV power supply, where the current is 100A. The train is travelling at 90 kmh−1. What is the net force exerted on it in a forwards direction?

/Worked Solutions/


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Talk:Fundamentals of Information Systems Security/Telecommunications and Network Security

There has been a suggestion Telecommunications Theory should be merged with Telecommunications and Networking pages. By Telecommunications here it is meant in the academic sense, i.e. the study of the effects of mass media on culture and communication. This is not what the telecommunications and networking area is. —Preceding unsigned comment added by Typewriter (discuss • contribs) 2008-04-07T22:18:05

 * OK, I'll remove the merge tags. Webaware talk 03:04, 9 April 2008 (UTC)


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A-level Physics (Advancing Physics)/Forces and Power/Worked Solutions

'''1. I hit a ball of mass 5g with a cue on a billiards table with a force of 20N. If friction opposes me with a force of 14.2N, what is the resultant acceleration of the ball away from the cue?'''

Resultant force = 20 - 14.2 = 5.8N

F = ma

5.8 = (5 x 10−3)a = 1160ms−2

'''2. A 10g ball rolls down a 1.2m slope, and leaves it with a velocity of 4ms−1. How much work is done by friction?'''

g.p.e. at top of slope = mgh = 10 x 10−3 x 9.81 x 1.2 = 0.117J

k.e. at bottom of slope = ½mv2 = 0.5 x 10 x 10−3 x 42 = 0.08J

Assuming the remainder of the g.p.e. becomes heat / sound due to friction:

work done by friction = 0.117 - 0.08 = 0.037J.

'''3. An electric train is powered on a 30kV power supply, where the current is 100A. The train is travelling at 90 kmh−1. What is the net force exerted on it in a forwards direction?'''

P = IV = Fv

90 kmh−1 = 0.025 km−1 = 25 ms−1

100 x 30 x 103 = 25F

F = 120000N


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Backpack Camping and Woodland Survival/Skills/Fire/Fire Starting/Bow Drill

The bow drill is an ancient tool. While it was usually used to make fire, it was also used for primitive woodworking and dentistry. It consists of a bearing block or handhold, a spindle or drill, a hearth or fireboard, and a simple bow. Related drills include the pump drill and the hand drill.

The spindle, carved to reduce friction at one end and maximize it at the other, is held at one end by the bearing block, and at the other by the hearth. The string of the bow is wrapped once around it, so that it is taut enough not to slip during operation. A variation on this called the Egyptian Bow Drill attaches the string in a slightly different way.

The usual position that a person assumes whilst operating the bow drill is as follows: the right knee is placed on the ground (assuming a right-handed operator) and the arch of the left foot is on the board, pinning it in place. The left wrist, holding the handhold, is hooked around the left shin so it can generate enough downward pressure and speed; achieved by pushing down with the handhold and spinning the drill. The heat of the friction between the hearth and the spindle both creates charred, fuzzy dust and causes it to ignite - forming a coal or ember. The handhold is lubricated and the spindle is carved to about thumb thickness, usually six to eight inches long.

An indentation and a "v" notch into the center of the dent is made into the fireboard and the spindle is placed on it. The notch allows a place for the dust collect while it is being abraded off the spindle and the hearth. Eventually, the friction generates heat to ignite the dust, which can be used to light tinder.

Whilst a "v" is most common, other methods to create a cavity to contain the dust whilst it is being ignited can be used. For example: drilling part-way into a hearth made by lashing two sticks together from one side, and then drilling from the other side to meet this hole; or using the area where two branches separate. This is to keep the coal off wet or snow covered ground.

This is by far the easiest method of producing a coal by primitive means and anyone can do it by using good materials and maintaining a calm mentality, concentrating only on working everything slowly and smoothly.


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Backpack Camping and Woodland Survival/Skills

Survival skills are skills that may help everyone to survive dangerous situations (such as storms or earthquakes), or in dangerous places (such as the desert, the mountains, and the jungle). Useful skills include lighting a fire, finding shelter, making water safe to drink, finding and identifying food, treating injuries, and climbing, swimming, and using specific or makeshift tools.

Each type of wilderness challenges a person with a different range of dangers (see hazards of outdoor activities). An environment may be dry, wet, hot, cold, high altitude, low altitude, desert, rural, urban, wilderness, subterranean, or an island. There are four basic necessities of life which apply in all of these cases: shelter, water, fire, and food. A fifth is oxygen for high altitudes and subterranean environments, and also specific survival situations such as drowning and landslide/avalanche.

Survival skills used on a more permanent basis, or as a component of daily life are referred to as bushcraft.

Developments in outdoor equipment and survival techniques have skewed the scale towards man- if one is prepared, but there is nothing to replace experience in a survival situation. Those who are most prepared physically and mentally stand the greatest chance of survival.

 * Water purification

Crafts

 * Tanning
 * Simple woodworking
 * Clothing
 * Weaving
 * Furniture
 * Packframes
 * Primitive knives
 * Bows and arrows
 * Staff making
 * Dreamcatchers

Clay Pottery

 * Pinch pots
 * Coil pots

Hunting and gathering

 * Primitive fishing
 * Hunting
 * Tracking
 * Traps and snares
 * Seasons
 * Safety and laws
 * Gutting
 * Skinning
 * Butchering
 * Cleaning
 * Field dressing
 * Gathering
 * Plants
 * Medicine

Fire

 * Safety
 * Prevention

Fire Starting

 * Bow drill
 * Hand drill
 * Pump drill
 * Bamboo saw
 * Flint and steel
 * Other methods

Cooking

 * Natural and harvested
 * Prepared food
 * Hallowing logs
 * Steam pits
 * Stone ovens
 * Cooking utensils
 * Cast iron
 * Sanitation and storage
 * Best practices


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IB Computer Science/Science Systems Life Cycle and Software Development

Return to IB Computer Science

Systems Life Cycle and Software Development

 * Topic 1.1 - Systems Life Cycle
 * Topic 1.2 - System Analysis
 * Topic 1.3 - Systems Design
 * Topic 1.4 - Social Significance and Implications of Computer Systems
 * Topic 1.5 - Software Life Cycle
 * Topic 1.6 - Software Design
 * Topic 1.7 - Documentation


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Backpack Camping and Woodland Survival/Skills/Fire/Fire Starting/Other methods

 * fire plow
 * potassium laminate and nitroglycerin
 * battery and finishing grade steel wool
 * magnifying glass
 * magnesium match
 * flares
 * Philippines sole pop fire starter
 * Swedish fire steel


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IB Computer Science/Computing System Fundamentals

OCR
Optical character recognition, usually abbreviated to OCR, its is used for translation of images of handwritten, typewritten or printed text. this is a field of a research in pattern recognition, artificial intelligence and machine vision. It is mainly based on the handwritten scripts.

Touchscreen
is a display which can detect the location of touches within the display area.They have many features as follows Resistive, Surface acoustic wave,Capacitive,Infrared,Optical imaging.Example of a touch screen application software will be Nintendo DS.

Keyboard
Keyboard is used for many function it helps us in different symbols; typically, this is because they are writing in different languages. There are many different types of keyboards, like wireless keyboards which increase the freedom of the user and it becomes more user friendly. Made up of any number of color or monochrome pixels arrayed in front of a light source or reflector The wireless keyboard signals are sent and received from both the keyboard and the unit attached to the computer.There many advantages of a keyboard as they have many special keys. There are lot of different types keyboard for example-Multimedia keyboards,Gaming keyboards,Virtual keyboards.

MICR
-Magnetic ink character recognition

Characters are printed in a special ink which contains tiny magnetic particles. A reading head is passed over the specially shaped characters and recognises the shape of each by its magnetic field. The computer can therefore capture the data printed in magnetic ink. MICR has the following advantages: It's both machine and human readable (unlike the magnetic strip on a credit card). The data can be read even if the paper on which it is printed is marked or folded. Due to the rarity of magnetic ink printers it is relatively hard to forge. It has the following disadvantages: A particular font has to be used so that it can be recognised, Exposure of the printing to a strong magnetic field can make the data unreadable (though it can still be keyed in).

Plotter
is a vector graphical printing device that connects to a computer. They can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pens. Plotters are not very efficient in their work as they cannot draw or create a solid region of color.

LCD
Liquid crystal display is a flat device and up of any number of color or monochrome pixels arrayed in front of a light source or reflection. There are many advantages of LCD Sharpness, Geometric Distortion, Brightness, Screen Shape, Physical. But there also some disadvantages of LCD Resolution, Interference, Black-Level, Contrast and Color Saturation, Motion Artifacts, Aspect Ratio.

Black-Level, Contrast and Color Saturation LCDs have difficulty producing black and very dark grays. As a result they generally have lower contrast than CRTs and the color saturation for low intensity colors is also reduced. Not suitable for use in dimly lit and dark environments.

Resolution
Each panel has a fixed pixel resolution format determined at the time of manufacture that can not be changed. All other image resolutions require rescaling, which generally results in significant image degradation, particularly for fine text and graphics.

Interference
LCDs using an analog input require careful adjustment of pixel tracking/phase in order to reduce or eliminate digital noise in the image. Automatic pixel tracking/phase controls seldom produce the optimum setting. Timing drift and jitter may require frequent readjustments during the day.

Black-Level
LCDs have difficulty producing black and very dark grays. As a result they generally have lower contrast than CRTs and the color saturation for low intensity colors is also reduced. Not suitable for use in dimly lit and dark environments.

Sensor
A sensor is a device which determines a physical quantity and transfers it into a signal which can be read by an onlooker or by an instrument. Sensors are used in our active life; for instance, infrared sensors are used in corridors to minimize the energy consumption. There are many different types of sensors as follows. Thermal, electronic, mechanical, chemical.

Optical radiation Light time-of-flight. Used in modern surveying equipment, a short pulse of light is emitted and returned by a retro reflector.

Advantages Smart sensor is an instrument which can transfer the information wirelessly to an Ethernet monitoring point.

Wireless sensor network is very friendlily instrument easy to install no wires are needed,it also allows an easy way for upgrading of existing unit.But there are some setbacks of wireless sensor it has a relatively slow speed of communication it also get sidetracked for example blue tooth.

=Graphic tablets = This is a computer input device which allows hand-draw images and graphics, similar to the way one draws images with a pencil and paper.It's a flat surface area on which you can draw, write, etc.

Mainly there are two types of graphic tablets: Passive tablet is electromagnetic induction .The tablet generates an electromagnetic signal, which is received by the LC circuit in the pen. The wires in the tablet then change to a receiving mode and read the signal generated by the pen.By the use of the electromagnetic signals the tablet is capable of using he stylus position without the stylus having to even touch the surface, and powering the pen with this signal means that devices used with the tablet never need batteries.

Active tablets This is little bit different from he stylus used contains self-powered electronics that generate and transmit a signal to the tablet.

Process architecture
is a process system which applies such as computer, hardware, software, networking. Process can be defined as having inputs, outputs and the energy required to transform inputs to outputs.

Architecture Besides a propensity to modeling dualistic real-world behavior, PNs also offer a way to manage complex process systems hierarchically. Using classical PN construction rules, Petri nets of Petri nets can be built and a hierarchical conception of a complex process system can be studied. This structure of hierarchical abstraction is the heart of process architecture.

A Hint from an ARKIS senior 2012 is also the processor architecture which is the single and multiple pipelines; the multiple pipeline works in parallel therefore increase the rate of intrruction bring processed.

Also guys don't forget the Primary Memory Architecture which is from an Known Examiner he told me that in May 2012 CS exam this will come ;) it's about the SRAM and DRAM. SRAM stands for Static RAM which is expensive however therefore used for Cache memory and the DRAM is usually used for main memory also don't forget the main development which is EPROM which allow users to write over ROM


text:
IB Computer Science/Computer Mathematics and Logic

Return to IB Computer Science

=Computer Maths and Logic=


text:
IB Computer Science/Abstract Data Structures and Algorithms

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=Abstract Data Structures and Algorithms=

Static data structures
You should be able to compile these examples in any Java editor, such as BlueJ or JCreator. All of the examples assume that the IBIO methods exist in the file.

An example class using these methods is found here. Make sure you can compile and run this source code if you want to implement any of the examples given in these pages.

Any code you want to try out should be placed in the Constructor:

/** public Adams {    // valid Java or JETS statements may be placed here... output("The answer is: " + d); }
 * Constructor for objects of class Adams

You may want to change the Class name, in which case, remember that:

the file name must be the same as the class name with the extension .java the constructor name must be the same as the class name. you ought to change the comments to reflect what your program does.

Stack in an array

An array is going to be used to hold a sequence of characters: [0] [1]  [2]  [3]  [4]  [5]  [6]  [7]  [8]  [9] [10] [11] stack

Initially, a pointer, size, is set to 0, so stack[size] is the next available element. To push an item onto the stack we can work one of two ways:

Allocate the item to stack[size] then move size up one in the array Allocate the item to stack[0] and increment size by 1

It should be apparent that the second option involves shuffling up elements whereas the first only requires the stack pointer to be moved.

Given:

private static final int SIZE = 12;     // a constant for the stack size private char[] stack = new char[SIZE]; // the array to hold the stack private int size = 0;                  // the number of items in the stack

A possible push operation is:

// method to push an item onto the stack public void push(char item) {          stack[size] = item; size = size + 1; }

Which works up to a point. Is there any check that needs to be done? Add it.

So far, the code might look like this:

/** public class Stack {  private static final int SIZE = 12;      // a constant for the stack size private char[] stack = new char[SIZE];  // the array to hold the stack private int size = 0;                   // the number of items in the stack
 * Class Stack
 * Implements a stack of Characters
 * Uses an array - is a static data structure

// Constructor public Stack {    size = 0; char c;    do     { c = inputChar("Input a character ('/' to end)"); push(c); display; } while (c != '/'); }  // method to push an item onto the stack public void push(char item) {    if (size < SIZE) {      stack[size] = item; size = size + 1; }    else {      output("Stack full"); }  }   public void display {    output("stack"); output("====="); for(int p = (size - 1); p >= 0; p--) {      output(p + ":> " + stack[p]); }    output("====="); }  // Main method for class stack public static void main(String[] args) {    new Stack; }  //============================================================   // Below are the IBIO simple input and output methods // to be included in the Class.

Exercises

Write the method pop, to remove an item from the stack - being sure to watch out for underflow (when there are not any items on the stack).

Write the algorithm which reverses a character String in place (a discussion of this is found on the previous page). To take an input String and split it into characters, you might need something like:

String s = input("Please input a String"); for (int p = 0; p < s.length; p++) {    char c = s.getChar(p); // process c

To concatenate characters into a String try something like:

String s;  char c;   s = s + c; // string s with char c added at the end (concatenated)

A useful method, top, returns the top element from the stack, if it exists, without popping it. Implement this.

Queue in an array

We have seen a possible way of implementing a queue using a linked list, but this section is concerned with static data structures. So let's see how we might go about using the same array as above, except that we will need two pointers into the array, front and rear.

Recall the items are added at the rear ( enqueued ) and removed from the front ( dequeued ). [0] [1]  [2]  [3]  [4]  [5]  [6]  [7]  [8]  [9] [10] [11] queue

It seems reasonable to have both front and rear point to element 0 initially. To enqueue an item, place it at rear then increment rear to point at the next free location.

Check to see if the end of the array has been reached:

public class Queue {  private static final int SIZE = 12;     // a constant for the queue size private char[] queue = new char[SIZE]; // the array to hold the queue private int front = 0;                 // the first item in the queue private int rear = 0;                  // the last item in the queue
 * Class Queue
 * Implements a stack of Characters
 * Uses an array - is a static data structure
 * Uses an array - is a static data structure

// Constructor public Queue {    front = 0; rear = 0; char c;    do     { c = inputChar("Input a character ('/' to end)"); enqueue(c); display; } while (c != '/'); }  public void enqueue(char item) {    if (rear < SIZE) {      queue[rear] = item; rear = rear + 1; }    else {      output("Queue full - cannot add item"); }  }   public void display {    output("front"); output("====="); for(int p = front; p < rear; p++) {      output(p + ":> " + queue[p]); }    output("====="); }  // Main method for class queue public static void main(String[] args) {    new Queue; } //============================================================ // Below are the IBIO simple input and output methods

Exercise

Implement the dequeue method, be sure to test if there is anything in the queue to remove.

You might want to change the Constructor to allow the dequeue to be called:

c = inputChar("Input a character ('/' to end, '#' to dequeue)");

You can either return a character from the dequeue method or output it within the method body.

Once you have got that working, there are a few problems here - try adding asnd removing enough items and we get to a point where the rear pointer has run up against the end of the array, yet there is still space at the front of the array: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] queue f s    s  a d	space which is unused/wasted front rear

So, what we need to do is wrap the front pointer around to the start again.

However, we have to be able to detect when the queue is full, when the rear pointer catches up with the front pointer.

There are several ways to deal with this problem, the simplest of which is probably to maintain a special flag qFull which we will set true when the front reaches the rear and unset whenever we dequeue an item.

It is also possible to use a qEmpty flag in a similar way.

/** public class Queue {  private static final int SIZE = 12;    // a constant for the queue size private char[] queue = new char[SIZE]; // the array to hold the queue private int front = 0;                 // the first item in the queue private int rear = 0;                  // the last item in the queue private boolean qFull = false;         // flag private boolean qEmpty = true;         // nothing in the queue initially // Constructor public Queue {    front = 0; rear = 0; qFull = false; qEmpty = true;
 * Class Queue
 * Implements a stack of Characters
 * Uses an array - is a static data structure

char c;    do     { c = inputChar("Input a character ('/' to end, '#' to dequeue)"); if ( (c != '/') && (c !='#')) {        enqueue(c); }      else if (c == '#') {        dequeue; }      display;

} while (c != '/'); }  public void enqueue(char item) {    if (qFull) {      output("Queue full - cannot add item"); }    else {      queue[rear] = item; rear = (rear + 1) % SIZE; qFull = (rear == front); qEmpty = false; }  }   public void dequeue {    if (qEmpty) {      output("Empty queue"); }    else {      char c = queue[front]; front = (front + 1) % SIZE; output("dequeued: " + c); qFull = false; qEmpty = (front == rear); }  }   public void display {    output("front"); output("====="); for(int p = front; p != rear; p = (p + 1) % SIZE) {      output(p + ":> " + queue[p]); }    output("====="); }  // Main method for class queue public static void main(String[] args) {    new Queue; } //============================================================ // Below are the IBIO simple input and output methods

Exercises

Write self-contained Queue Class that can enque and dequeue Strings or other Objects of your own choosing.

The Class should implement Exception handling so that EmptyQueue, FullQueue and other custom exceptions can be thrown.

Additional methods mught be getFront, getRear to examine, but not remove these items. A method to return the current size of the queue would also be useful.

Recursion
Example (Java):

This is a simple code to represent the value of factorial.

Efficiency of Algorithms
To optimize algorithms, one must first know whether a certain algorithm is better or worse than another one. In this case, better can mean that the algorithm processes data faster or that less RAM is used. To measure data processing speed, one can use Big O notation.

Big O notation is always in the form of O(expression). The expression inside the parentheses is different for different efficiencies. It almost always contains $$n$$, the number of items of data to be processed. The Big O notation of a linear search on an array (of size n) is O($$n$$). This means that doubling the array size will, on average, double the time for the linear search to complete.

Big O notation does not, however, indicate exactly how efficient an algorithm is. It only indicates how much the time spent increases when $$n$$ is very large and is increased. For instance, if a certain algorithm takes $$0.5n + 2$$ milliseconds for each item of data, it will still have a Big O notation of O($$n$$). This is because when n gets to, say, one trillion, the added 2 will have almost no effect, so it is discarded. In the same way, all coefficients of n are discarded.

Other examples of Big O notation include O($$n^2$$) for bubble and selection sort and O($$\log n$$) for binary search. Note that binary search’s Big O notation is $$\log n$$ instead of $$\log_2 n$$, because logarithms of different bases increase in approximately the same way when $$n$$ is large.


text:
IB Computer Science/Further System Fundamentals

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=Further System Fundamentals=

Instruction Register
An Instruction Register is the part of a CPUs control unit (as seen below) that stores an instruction. The bits of the instruction register are decoded by a microprogram that controls the computer.

Accumulator
An Accumulator is a register within the ALU (as seen below). It temporarily stores the data from an arithmetical or logical operation, and then writes it to main memory or to another, non-accumulator CPU register (depending on what it is told to do).

Program Counter
A Program Counter is a register located in the CPU (as seen below). It is used to hold the address of the next instruction to be fetched from the immediate access memory for execution by the computer.

Magnetic Disk Storage
The most common physical device for storing files is the magnetic disk. A magnetic disk has one or more platters in the form of disks, covered with magnetic media. Hard disk platters are made of rigid metal, while floppy disks are made of more flexible plastic. Each platter on the magnetic disk has two working surfaces. Older hard disk drives would sometimes not use the very top or bottom surface of a stack of platters because they were more likely to be damaged.

The surface of a platter is organized as a number of round rings, called tracks. The group of tracks immediately above one another (as seen in the diagram below) is called a cylinder.

Furthermore, each track is divided into sectors. The information held in one sector, a block, is the unit of transfer between the disk and primary memory (normally 4K bytes or so). The operating system determines where the blocks for each file are placed.

The data on a magnetic disk is read by read-write heads. The standard configuration (as seen below) uses one head per surface, each on a separate arm, and controlled by a common arm assembly which moves all heads simultaneously from one cylinder to another.

The rate at which data can be transferred from the disk to the computer is composed of 3 different steps:

All these times are of the order of tens of milliseconds. The seek time and latency time vary, depending on where the required block is relative to the current position of the heads. It's useful to put all the blocks of a file on one track, to minimize seek times and latencies in accessing the file. Likewise, for a larger file, it's a good idea to have it all on the same cylinder (a set of corresponding tracks on different platters). There are many other placement tricks (such as placing heavily used files on the middle tracks so that the average seek time is reduced). However, since files are of varying sizes, and can change size dynamically, it's not usually possible to place the blocks optimally.

Handshaking
The definition of handshaking is described as when one computer is establishing a connection between the other computer or any other device that wants to connect to the computer. The handshake can be brought down into steps such as it will verify the connection, the speed and the authorization of the computer that it is trying to connect to. Example: When a modem connects to another modem, the dialling is the handshake between them. Modem handshakes can be muted by going to the control panel.

Port
The port connection is commonly found behind the back of the computer it usually resembles a plug-in. Hardware ports allows it to access to external devices. Such as USB, printers, mouse.

When referring to the internet or the network, a network port is a location where the information is sent. A more commonly used port is the http which is port 80. Which is commonly known as the Virtual Port.

A common way to manage a transfer is to provide a status in bits, which will be sent to a secondary input port. An example would be, a one in a single bit can tell the CPU that the printer is ready to take in more data. If a zero appears it would tell the CPU that the printer is busy therefore the CPU should not send any new data just yet. Another example would be if one bit in a different port could tell the CPU that a keystroke is hit and it is available at the data port. If the zero is shown it means that there was no keyboard stroke.

An image of a printer port

Virtual Port
A virtual port is an emulation of the serial port. The port can be created by a software which will enable extra ports in the system. A virtual port can be given any name (COM1337, VSP11, etc). There can be an unlimited number of virtual ports in your PC. The more ports the less computer performance it has.

Virtual ports copy all hardware serial port functionality, including Baud rate, Data bits, Parity bits, Stop bits, etc. They control the data flow, copying all signal lines (DTR/DSR/CTS/RTS/DCD/RI) and customizing pinout. A common virtual port is Bluetooth. A virtual port can be useful if there are less physical ports on the computer. Another use of a virtual port is to communicate with other serial devices via the internet or LAN and act as if they were connected together. Such examples can be found in applications such as Hamachi and Garena. Links: [www.garena.com], [www.hamachi.com]

Buffer
A buffer is a part of the memory used to hold temporarily data while it is moved from one place to another. The data is stored in a buffer which will then be received from an input device such as a keyboard to an output device such as a printer. When a data is moving between processes in a computer a buffer is also used. This can be related to buffers in telecommunication. Buffers can be found in a hardware or software but it is mostly implemented in software. If the data that is being transferred has a different rate at which it is received and processed, then the buffers are typically used in a scenario such as this. Buffers are in a combination with the I/O to hardware, such examples are the disk drives, sending and receiving data from one place to another, or playing sound on a speaker.

Buffer and the Cache
Some cache acts like a buffer. But it is not exactly the same, a cache operates on the premise that the same datum (plural for data) will be read from multiple times. The purpose of a cache is to reduce accesses to slower storage. A Cache is an abstraction layer meaning that it is a way of hiding the details of a particular set of functionality. Such as the OSI 7 Layer Model.  A OSI 7 Layer Model

Data Transfer
Computers always need to transfer data with other external devices (Input/Output devices). There are two different ways for transferring the data between computer memory and external devices:

PIO
PIO (Programmed I/O) is a method in which processor keeps on reading or writing on a memory unit (8-bits, 16-bits or 32-bits, depending on the device interface) until the data transferring is completed. Obviously this method consumes a large amount of processor cycles. There are several different speeds of PIO, knows as programmed I/O modes, or more commonly, PIO modes. Table below shows five different PIO modes:

PIO was the only method for transferring the data between devices and IDE/ATA hard disks through the mid 90s. Three lower-speed modes (Mode 1, Mode 2, Mode 3) were defined as part of the original ATA standards document; two more (Mode 4, Mode 5) were added as part of ATA-2 (as well as part of several unofficial standards.)

Direct Access Memory
DAM (Direct Access Memory) is a capability that allows the data on an external attached device (such as a Disk Drive) to be sent directly to the computer's memory on the motherboard. In DMA method the system issues an I/O command to the device, initiate a DMA transaction and then place the process in a waiting queue and the processor will be free afterwards to do other transmissions or execute codes. The DMA controller will inform the system when its current operation has been completed by issuing an interrupt signal. Although the data is still transferred 1 memory unit at a time from the device, the transfer to main memory now circumvents the CPU because the DMA controller can directly access the memory unit.

 Let's go more in depth!

As it was mentioned in DMA method the processor is not involved during the whole transmission; but it only initiates the transmission and after that the data can be transferred directly from or to the main memory. But how do the CPU do that? To initiate a transmission the processor should load three different values into three different registers in the DMA controller. These values are: 1- identity of the source device 2- the location in memory where the data transfer begins 3- the number of bytes to be transferred The DMA controller then collaborates with the IO unit using the control lines on the bus to perform the handshaking protocol for managing the data transfer. When the transfer is complete, the DMA notifies the CPU via an interrupt. With the DMA, data does not pass through the CPU registers, but directly along the bus from source to destination.

Direct Access Memory
Direct memory access also known as DMA is a feature of modern computers. Within certain computers the hardware subsystems has its access system memory which is used for reading and/or writing independently of the central processing unit(CPU). Many systems use DMA, such example could include disk drive controllers, graphics cards, network cards, and sound cards. Computers that have DMA can transfer data from devices with less CPU overhead than computers without a DMA channel.

Without the DMA the CPU would be fully occupied for the entire duration of the read and write operation and it would not be able to do any other work. The DMA can start transfer, operate programs, and receive and interrupt from the DMA controller. Which can be useful to real-time computing.

 Vote! Can you please vote and tell us which definition for "Direct Access Memory" is more clear to you? You can respond in the discussion section.

Polling and Interrupts
One of the duties of the processor in the computers is to manage the devices and programs and since there are many devices connected to the processor and also so many programs (those are running on the OS) the processor needs to be able to figure out what should it do in each moment. Two different ways of doing this are Polling and using Interrupts.

Polling
Polling is a method in which the processor checks every single device's current status in a loop and looking for data. When new data is available on one of devices it can then read the data and process the incoming bytes. However this method can work to manage the devices and programs, there are some big problems with it. First, the processor would always be busy with checking all the devices and programs instead of processing data and executing some useful codes. Second, in this method it is very likely that some of arriving bytes are lost when the rate of transfer data is too high.

Interrupts
An Interrupt is a signal from a device attached to the computer or a program that is sent to the OS (Operating System) and causes it to stop and figure out what to do next. Interrupts initiated by hardwares are called Hardware Interrupts while the interrupts that have been made by programs are called Software Interrupts, traps or exceptions. An average PC supports 16 hardware interrupts and 256 software interrupts. Each type of exception (Software Interrupt) is associated with a routine that takes control when an interrupt occurs. This routine is called Interrupt Handler. An Actual interrupt that is sent to the processor is called an IRQ (Interrupt Request). Each IRQ is a binary code that differs from other interrupts and the processor uses these binary codes to distinct different interrupts. However these interrupts may be different for each device and processor but they usually follow a standard. The typical Hardware Interrupts have been shown in the table below :

When one of the Input or Output devices sends an interrupt to the CPU, before the processor catches it, that IRQ goes through a chip called PIC (Programmable Interrupt Controller). The PIC selects an IRQ from the highest priority device to pass to the CPU and if the processor is ready to accept that IRQ, the PIC sends it to the CPU. The processor has a flag that illustrates whether or not it is ready to accept IRQs. If the CPU catches the request (because as it was mentioned it can also ignore a request) it temporary stops what it is currently doing and executes the proper code related to that request. When the ISR is completed, the CPU returns to the program it was executing and resumes its previous task.

 How to find out your PC IRQs? Windows In order to find the IRQs of your devices in windows, open the device manager (you can either right click on MyComputer -Or Computer in Windows Vista- and then click on properties. Then Click on the Device manager. Or simply search for device manager in your computer). Right click on any device and in the form that is opened go to the Resources tab and look at the binary code in fromt of IRQ. Linux For most distributions this will work: # dmesg | grep irq

Serial and Parallel Transmission
Data are transmitted through a communications medium, they are either sent in serial or in parallel transmission. Most of the owners of microcomputers know that their computers are equipped with serial and parallel ports. In which it will enable the computer to transmit both serial and parallel signals.

In both of the series, the bytes that are sent are sent along a medium. For example if it would send “SYAMIL”, it would sent the “S” first, then “Y” then “A” and so on this goes for serial. As for parallel transmission, they are sent separately, the parallel paths correspond to each bit of a byte so that all of the bits would arrive simultaneously.

Since parallel is more efficient then serial, it would need more wiring and extra bit paths, besides that it is more expensive then serial. Devices that are located near each other usually will use a serial transmission. For example, a parallel transmission computer would send a word document to a printer that it is connected to.


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IB Computer Science/File Organization

Return to IB Computer Science

=File Organization=

title: IB Computer Science/File Organization


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Backpack Camping and Woodland Survival/Emergency Techniques/First Aid

First aid (wilderness first aid in particular) can help a person survive and function with injuries that would otherwise kill or incapacitate him/her. Common and dangerous injuries include:

Lacerations, which may be infected

Bites from venomous animals, such as snakes

Bone fractures

Sprains, particularly of the ankle

Burns

The survivor may need to apply the contents of a first aid kit or naturally-occurring medicinal plants, immobilize injured limbs, or even transport incapacitated comrades.


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When It Hits the Fan/Personal Strategies and Know-how/Navigation

Navigation skills
Survival situations are resolved by finding one's way to safety. This requires some navigation or movement:

Celestial navigation

 * using the sun and the night sky

Reading a map

 * particularly a topographic map together with a compass


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Spanish/Contents/Valuable noun-related phrases

The following are phrases built around nouns to assist beginners in learning both nouns and the present tense and past tense usage.

 * Yo tengo una pluma. = I have a pen.
 * Este soy yo. =  This is me.
 * Tengo hambre = I am hungry
 * Tengo sed = I am thirsty.
 * una manzana = an apple
 * una uva = a grape
 * una sandía = a watermelon
 * el mango = the mango
 * la naranja = the orange
 * la toronja = the grapefruit
 * la pera = the pear
 * la fresa = strawberry
 * la carne = the meat
 * el pollo = the chicken
 * la leche = the milk
 * el jugo = the juice
 * el agua = the water


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Backpack Camping and Woodland Survival/Skills/Cooking

Navigation Various types of equipment are used in a kitchen. One of the Wikibooks Cookbook's goals is to have an article on each, including uses, alternative equipment if you don't have the exact item, and a buying guide. The various equipment modules can be reached from the following organization pages. Pots and pans hold food, generally for cooking on a firepit. Dark gummy burned-on oil can be removed with acetone, widely available from hardware stores and in diluted form as nail polish remover.
 * Natural and harvested
 * Prepared food
 * Hallowing logs
 * Steam pits
 * Stone ovens
 * Cooking utensils
 * Cast iron
 * Sanitation and storage
 * Best practices

Food is not urgently needed in survival situations, since a human can survive for several weeks without it. However, much like dehydration, hunger can bring about many consequences long before it causes death, such as:  Irritability and low morale Weakness Loss of mental clarity, such as confusion, disorientation, or poor judgment Weakened immune system Difficulty maintaining body temperature (see heat exhaustion and hypothermia)

It is actually rather easy to find food in most wild environments, provided one knows where to look. A basic knowledge of animal trapping, hunting, and fishing will provide meat. Equally important is a knowledge of edible plants, fungi, and lichens. One cannot always rely on the most abundant or most easily accessible type of food. To survive for long periods of time, one must maintain a balanced diet. In order to do this, one must consume a balanced variety of foods.

Finding food in the wild depends on your environment (i.e. vegetation, animals, and water sources). Many survival books promote the "Universal Edibility Test": allegedly, one can distinguish edible foods from toxic ones by a series of progressive exposures to skin and mouth prior to ingestion with waiting periods and checks for symptoms. However, many other experts including Ray Mears and John Kallas reject this method, in main part because a very small amount of some "potential foods" can cause anything from gastric distress to illness or death. An additional step called the "scratch test" is sometimes included. In this step (before mouth contact of the proposed food) one makes an abrasion on the surface of an area of skin (such as with fingernails) and then lightly rubs some of the food product on the abrasion. Foods that cause surface inflammation, discomfort, itching or eruption should be avoided.


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Backpack Camping and Woodland Survival/Skills/Water Purification

A human can survive a maximum of three days without the intake of water, assuming you are at sea level, at room temperature, and a relative humidity. When camping in an area that does have running water, make sure that it is OK for drinking. If you see a sign that says "Non-potable Water," that means that it is NOT OK to drink. Rather, non-potable water is only suitable for flushing toilets and washing hands.

When camping in an area that does not have running water and toilets, you must either bring water with you, or bring along the means for purifying water you collect when you arrive. Do not assume that because a stream or lake looks clean that it is OK to drink. In general, it is not, and drinking it without treating it carries a high risk of causing diarrhea or vomiting. Do not brush your teeth, cook with, or drink non-potable water without purifying it first.

In colder temperatures and/or with rain or snow the length or likelihood of survival would be greatly reduced. In addition to the aforementioned priorities, length of survival also depends on amount of physical exertion. A typical person will lose 2-3 liters of water per day in ordinary conditions, but more in hot, dry, or cold weather.

A lack of water causes dehydration, resulting in lethargy, headaches, dizziness, confusion, and eventually death. Even mild dehydration reduces endurance and impairs concentration, which is dangerous in a survival situation where clear thinking is essential. Your body requires 4L to 6L of water or other liquids each day in the wilderness to avoid dehydration and to keep your body functioning properly.

Dark yellow or brown urine indicates dehydration. Because of these risks, a safe supply of drinking water must be located as soon as a shelter is built (or even before, depending on conditions).

Acquiring water
Water can be gathered in numerous ways: scooped out of a creek or pond; rainwater can be caught in makeshift containers; collect dew from vegetation in clothing articles. Many tree roots and vines contain water, however water from poisonous vegetation can be lethal. Nonpoisonous cactus is also a source of water, confirming the myth- pulp can be removed from the broken stem.

In a survival situation, any water supply may be contaminated with pollutants or pathogens (see Potability of backcountry water). Although little can be done to remove molecular contaminants, particles and microorganisms can be removed and/or killed (see Portable water purification). In a beach situation, digging in the sand below sea level, the sand well will fill with drinkable water; it may taste salty or brackish, but the sand acts as a filter reducing the salt content the further you dig inland. Stagnant water can be made drinkable by filtration through a sieve of charcoal.

Animal blood is not suitable for rehydration as it may be diseased. In addition, because of the nutrients it contains, it requires energy to digest. Mammals all have blood-borne pathogens so the animal must also be cooked. Urine contains salt and other toxins, which also makes it unsuitable to drink, although it can be refined in a solar still.

Many birds, mammals, and some insects, such as bees, ants, and mason flies, are reliable indications of water, either through a stream or a soaked patch of earth.

The U.S. Army survival manual recommends that you use your water whenever thirsty to avoid "voluntary" dehydration. Other groups recommend rationing water through "water discipline".

While finding water is most important, preventing water loss is also an issue. Resting, avoiding smoking, and breathing through the nose are recommended.


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Backpack Camping and Woodland Survival/Shelters

Navigation A shelter will protect one from potentially disastrous weather, help prevent hypothermia, and allow restful sleep. It will also boost how you feel emotionally, as it will become a base or home. Therefore, in typical survival situations, a shelter should be able to be moved with you, if possible, and be set up quickly. If one spends too much time on a shelter it takes away from other survival tasks.
 * Natural Shelters
 * Caves
 * Quick Shelters
 * Lean-to
 * Tents
 * Tipis

Immovable rocks, animal nests, and other obstacles and hazards should be avoided.

Dry watercourses may be flat, sandy, and comfortable to sleep on, but they will flood in a storm.

Sunlight provides warmth (which is not always welcome), and can help one to wake up in the morning. However, sunny, open areas are vulnerable to wind which causes convection of one's body heat.

Heat transfer: an excessively large or well-ventilated shelter will not retain warmth well.

Flashing (weatherproofing) to provide protection from elements. A cave can provide a very useful shelter because it can provide protection from wind, rain and snow and maintains a constant internal temperature. Unfortunately, caves can present additional problems such as ground water, dampness, disease, and wildlife. Histoplasmosis, Blastomycosis, and Coccidiomycosis are several fungi found in caves that can infect the eyes and lungs of cavers. If bird or bat droppings are prevalent, you may want to find a different survival shelter to avoid these fungi. Bats often roost in caves and through their bite they can transmit rabies and other terminal illnesses. Bears also make dens in caves, so before you settle down in one, you should check it thoroughly for signs of inhabitance.

The simplest and most mobile shelter is a tarp, supported by make-shift frame work or rope. Large leaves, such as ferns or fir branches, can be added to a latticework of branches. Ferns on a shelter provide insect repellent. Branches propped against a fallen tree make a simple and effective refuge, but animals such as ants and snakes may nest under the tree.

A more advanced shelter is known as a debris shelter, which can be constructed without modern tools or implements. It consists of a central ridge pole supported by two forked poles. This ridge pole supports a lattice of branches, which is then finished by leaves or other insulating material.


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When It Hits the Fan/Generalities

Step One: prepare for something small.
Survivability depends on what you know, how fit you are and available tools and resources. Fitness is the most important factor, if you are fit you can cope with mistakes and exert more effort to gather resources. The next important trait is having useful knowledge, this prevents making mistakes, reduces wasted energy and helps to keep moral up. It also serve to increase the chances of surviving without tools or resources. If you know how to improvise your own tools and locate water and food you have not only gained time but increased your value to others and you will have an advantage over any competition (including wildlife).

By having tools and resources you will be less dependent on others, reduce your movements/efforts and have something to bargain with if need arises, even for your life. Depending on the situation this can makes you also a bigger and slow target, especially if because of them you became static, for example not leaving your house amidst a flood or an epidemy because of excessive reliance/dependency on what you have stored. Balance is of the essence.

Knowledge
Be aware and informed. What could be an usual emergency? Some emergencies are indeed expected to occur. It might be a flood, a hurricane, a tornado, or an earthquake. All this things have a distinct and knowable risk factor, even if unpredictable, some events are dependent on specific geographic location. Do you live near a river bed ? A atomic power plant?

Knowing your surroundings and local risk factors will always help you be prepared and safer and should be also a factor for you daily decisions. Be aware of emergency plans for the area where you live, work or visit and learn the general actions that increase survivability in the expected regional emergencies (higher probability), like how to act in an earthquake or a tsunami if that is the case.

There are many information and know how that is very low in complexity and can prove indispensable in a large array of situations. You can easily get some camping experience, practice and learn how to tie different utilitarian use knots, to create fire (especially using only wood) even learn how to meditate (or hypnosis). Knowing your blood type, allergies, the basics of first aid, learn how to swim and fish, how to can food and safely use it, to handle firearms and bows, repair a car and drive it, ride a horse or bicycle, all this type of knowledge will help you be more self-reliant and independent and so increase your chances in a myriad of unforeseen situations.

Experience
There is no better thing that first person experience, this is the best way to not only learn but understand your limits and find new ways to solve unexpected problems. It will help everyone survive dangerous situations (such as storms or earthquakes), or in dangerous places (such as the desert, the mountains, and the jungle). Useful skills like lighting a fire, finding shelter, making water safe to drink, finding and identifying food, treating injuries, and climbing, swimming, and using specific or makeshift tools.

The more experience one has the more self confidence and keeping the moral up it is. In order to overcome the effects difficulty it is important to study and understand how stress may affect your action in both good and bad ways.

Backpacking
Having an understanding about your priorities, the needed supplies to address your requirements is extremely useful. Management of resources and deciding how and what to carry is a science in itself. There is a large quantity of books that deals exclusively with this subject directed to specific target audiences, in special to the habitual traveler but also for the wildlife experience. How and what to pack is a learning process that improves with experience.

Backpackers use lightweight equipment that can be carried long distances on foot, this may include a tent or shelter. Enabling a person to hike across the land, camping at remote spots. Backpacking equipment typically costs more that other type of equipment because of the materials used (resistance and weight) and the necessity of self reliability (like including their own power-supply).

Camping
Camping and other outdoor recreational activities are great to build self reliance and confidence. It can even provide the experience of being away from civilization. Camping may involve the use of a tent, a primitive structure, or no shelter at all.

Canoe camping is similar to backpacking, but uses canoes for transportation; much more weight and bulk can be carried in a canoe or kayak than in a backpack. Canoe camping is common in North America.

Anther form is the bicycle touring that combines camping with cycling. Where a bicycle is used to carry the gear and as the primary means of transportation, allowing greater distances to be covered than backpacking although less capacity for storage.

Motorcycle camping is more comparable to bicycle camping than car camping, due to the limited storage capacity of the motorbike. Motorcycle camping riders, as well as bicycle touring riders, often use some of the same equipment as backpackers, due to the lighter weights and compact dimensions associated with backpacking equipment.

"Winter Camping" refers to the experience of camping outside when there is sufficient snow on the ground. Some campers enjoy the challenge this form of recreation brings.

Wild Camping too, is a growing choice by people seeking the challenge of camping in the wilderness, without campsite amenities. It is a great way of enjoying the solitude and beauty of the wilderness in its most pure form. It falls into the survivalist experience.

Survivalists
Survivalist can be defined as experience campers that have learned the skills needed to survive out-of-doors in a situation of scarcity. It require skills in obtaining food from the wild, emergency medical treatments, orienteering, and pioneering. Skills used on a more permanent basis, or as a component of daily life are referred to as bushcraft.

Campers and outdoors people have adapted their forms of camping and survival to suit extremely cold nights and limited mobility or evacuation. Methods of survival when winter camping include building snow shelters (quinzhees), dressing in "layers," staying dry, using low-temperature sleeping bags, and fueling the body with appropriate food.

Practicers of this type of wilderness challenge face a different range of dangers. An environment may be dry, wet, hot, cold, high altitude, low altitude, desert, rural, urban, wilderness, subterranean, or an island. There are four basic necessities of life which apply in all of these cases: shelter, water, fire, and food. A fifth is oxygen for high altitudes and subterranean environments, and also specific survival situations such as drowning and landslide/avalanche.

Developments in outdoor equipment and pruning of survival techniques have skewed the scale towards man- if one is prepared, but there is nothing to replace experience in a survival situation.

Bushcraft
Bushcraft is a long-term extension of survival skills. A popular term for wilderness skills in Australia, New Zealand and South Africa, the term was popularized in the northern hemisphere by Mors Kochanski and recently gained considerable currency in the United Kingdom due to the popularity of Ray Mears and his bushcraft and survival television programs.

Bushcraft is about surviving and thriving in the natural environment, and the acquisition of skills and knowledge to do so. Bushcraft includes all of the survivalist's skills but also includes more complex knowledge; firecraft, tracking, hunting, shelter building, the use of tools such as knives and axes, foraging, hand-carving wood, container construction from natural materials, rope and twine-making, and many others.

Things you should carry with you at any time
Strive to at all times carry simple items that in a SHTF situation may make you life easier.

I keep small tins and in them individually I have mini-kits that stow easily anywhere and everywhere - in a purse, backpack, under the seat in the car. In them I carry the following items - a magnesium fire starter block with a metal scraper attached - can be got at hardware store, outdoor shop - its about 3 inches by 1/4" wide with a flint down one side, the metal scraper lets you shave off pieces and then you can strike the flint with it or against a piece of granite to generate a spark - starts a fire even with wet material, use with care as magnesium flares hot and fast. Super inexpensive they can be got on sale for about $3 or regular price about $8. In another small tin I have several fish hooks of various sizes, fishing line wrapped around a short piece of dowel or anything that lets you wrap about 20 ft of line -even a piece of stiff card will do. I include small split sinkers, a couple of little jig heads and small (1 to 1 1/2 inch) colored plastic baits, several shiny spinner pieces - just the metal - they sit flat in the tin. In another tin I have water purification tablets and a bottle of nascent iodine. I also have a tin with small multi-tools in them - there's a great one out for about $5-$10 that is flat about 2X3 inches and 1/16th thick of stainless steel that has 8 different functions. Have a look around at your local hardware store, sporting good stores. I've always got room for my kits - total investment is very small for extremely useful and potentially life saving items that can be kept in multiple locations so that you're more likely to have them close to hand than all packed in a nice bag in the closet at home. I've also picked up about 5 or 6 woven bracelets from the dollar store. The bracelet looks nice enough in neutral colors and is made of parachute cord. It pulls apart to provide 8 to 12 ft of tough cord. They fasten with a plastic lock snap and I keep one on the gear shift, one on my backpack strap, you get the idea. And I've got FirstAid tins - few bandaids, butterfly closures, alcohol swabs, safety pins, emergency blanket (those thin foil sheets that fold up to the size of a dollar), on old mirror from a compact, a whistle and a small plastic compass about the size of a quarter. I keep an eye out for tobacco tins, playing card tins, etc. you can decide what size tins you want to use - anything from a cigarette tin to larger ones and they are easy to find at garage sales, flea markets, dollar stores, 2nd hand stores, even your neighbor might have some they are throwing away - just start looking and you'll be surprised where you'll see them. With my tin kits in multiples, stashed on my person, and in different convenient places like the car and a backpack, my favorite slouch purse, I'm more likely to have emergency basics at hand than have a big go bag packed in my closet that's no good to me cause I likely won't be sitting home when It Hits The Fan. My little tin kits cover all the main emergency basics and don't take up a lot of room. Low cost, low hassle, takes up little room, and its been fun putting them together and playing my what if games cost, low hassle, take up small bit of space whether in a backpack bundled together - in the pockets of my favorite slouch purse. I also play a little game to keep myself alert and thinking and can be played anywhere - out for a walk in the park, on a hike in the forest, driving down the highway (don't get too distracted) of looking around my immediate environment and seeing what is there to scrounge/salvaged/items that can be used for purposes they're not made for, what the lay of the land is if I had to abandon my car, or what would be a good place to shelter for the night. I find it keeps my frame of mind positive as well, and you can carry a positive, can do attitude around with you everywhere you go. Hope someone finds this helpful - I'm not waiting for an apocalypse, but a severe weather event like SuperStormSandy or Katrina could be coming my way anytime. Since I began making up my tin kits, I find my confidence level has increased, I've learned a lot of new things, and it reduces fear. One last thing - get out and get comfy trying out your little kits, see what works, what can be improved, what challenges there are to using them instead of waiting til It Hits the Fan. Don't wait for a hazard to unfold to get a feel for your kits and tools.

One type of object that should normally be carried is small or dividable item of tradable value. For instance a bracelet or necklace of gold or silver can be easily hidden and designed so links can be loosen to permit smaller trades in case of need or be used as bait for fishing. Depending on the situation most other items you carry can be used for trade, like a watch or even your shoes.

A good resistant belt, preferably longer than required. The belt buckler can also be a good tool beyond its primary function. Note that a belt can be a rapid way to create a tourniquet, to increase your reach or even to use as support in a zip line.

A time keeper, pressure resistant, non digital wrist-watch (or even better a chain-watch), that does not depend on batteries will be extremely helpfully and as seen above be an easily tradable item, it can also serve as a compass with the help of the sun, and will permit you to keep to a time table so to improve survivability.

For instance in a forest you may not be able to see the sun and in a survival situation you should keep night movement to a minimum, depending on the available light (moon, possibility to make and the duration of a torch) and expertize in night navigation. Even in a desert environment where nights will be cooler, and movement easy, it may not be advisable. A time keeper may also help avoid the hours of the day that temperatures are higher.

A small and reliable knife, is extremely useful in any situation even for day-to-day life, for instance in your key-chain. Not only useful as cutting tool or a possible weapon, the metal of the knife may also serve to create fire and serve as a crude mirror for signaling.

Things to plan at home
Your home should be your base in an emergency. Ownership of the property should be a priority so you have full legal control over it and in dire circumstances no one will be able to claim if from you.

Select a property that is not in a flood basin or too near a river (or any water course), if it is, check historic records for the area and see if you can build it (or if it already is) well above the flood line. Having at least one inflatable boat will also be optimal. Note that this type of location it will prevent you to rely on a well for fresh water since there is a high degree of contaminants that can already be present of the natural water system or will be carried by any flood, as also make any food planting very susceptible to damage. Near the coast line you will have aggravated problems due to humidity and the presence of salt.

In a location with a high probability of heavy snow, at least one of the doors should open inward and preferably be in the 2-split format, this will prevent you becoming snowed in. Same is valid in areas prone to dense sandstorms.

Assume 2-3 days without power and plan for that. This implies having three days of food that does not need cooking or refrigeration. Keep extra water put aside, flashlights, radio.

Step Two: supplies and more
Planing for supplies is extremely important and constitutes an economical investment. Any item should be considered on the basis of its longevity, hardiness and usefulness.

Human survival priorities are found in the "Rule of Three":
 * Humans cannot survive more than three minutes without air (O2)
 * Humans cannot survive more than three hours exposed to extreme low temperature
 * Humans cannot survive more than three days without water (H2O)
 * Humans cannot survive more than three weeks without food

There are also optimal times and locations to get your provisions for that special emergency or specialized material, consider that prices fluctuate with seasons for instance in the end of summer and winter season you can get good prices in sporting goods for the season that is ending.

Step Three: protection
Now you have something worth defend, something that others less prepared my be willing to fight you for. Huddling in the your "cave" fearing the unknown is an unsettling feeling. How does one combat this? Depending on your frame of mind, this is either the most frightening or most exciting part of preparedness steps, you will, in most events be dealing with the most dangerous animal on Earth, man.

In most locations and if not when involved in a catastrophic situations one may rely in the Police (or other state forces) since the event will not be disruptive enough to make it impractical or place your personal security at a low priority, making you dire situation not particularly relevant in the general context of things.

Protection is a defensive stance, the tool-set may serve other purposes but consider this factor when you plan, since it is linked to what you have a need to protect.

It is always best to be self reliant, by having a self sufficient strategy for active protection of your self, yours and your resources should be part of your survival strategy, this will help you fight off any intruder or scavenger be it human or beast.

Next... Reality Check
The most important factors for survival are shelter, water and food, by order of importance. In most situations if you are exposed you will be in danger from the involvement, be it hostile or not at the time you see yourself in dire straits. The sooner you find a safe place and establish the minimum to shelter you from the environment the better changes you will have.

The next priority is locating a water source, without water you will quickly become dehydrated and unable to function, water has also the property to reduce the sensation of hunger (especially if you can warm it).

The last step to become self sufficient is food. These are the three things that will have primal importance in any situation, being deprived of anyone of them will assuredly put your life in danger.

When It Hits the Fan/Teaming Going solo versus joining with family, a small team or a wider group.

When It Hits the Fan/Morals and law

title: When It Hits the Fan/Generalities


text:
IB Computer Science/Science Systems Life Cycle and Software Development/Systems Life Cycle

System Life Cycle Stages
The systems life cycle can be broken down into five stages: Analysis, Design, Implementation, Operation, and Maintenance.

 * 1) Analysis - The system analyst meets with the users to determine exactly what the user wants, and undertake feasibility studies (whether it is possible for the designers to meet the user's expectations).
 * 2) Design - In this stage, the programmers design a solution to the user's problem. This can be the most time-consuming part of the cycle, since there are many choices that need to be made. A decision must be made on the types of software, hardware and on the algorithms that are going to be used.
 * 3) Implementation - The construction (development) of the system; the system is developed based on the design laid out in the previous stage.
 * 4) Operation - Also known as installation, or system launch. The system can be installed as a direct changeover, as a phased introduction, or as a parallel running.
 * 5) Maintenance - Bugs and/or flaws might arise with time, thus, the system will need to be fixed and updated. However, fixing one bug may lead to another bug being created.

Importance Of Collecting Data
Gathering data is essential in the analysis stage because you can gain clear insight into the problem. If the problem cannot be identified correctly, a poor solution is guaranteed to follow.

Production of Requirement Specification
A requirement specification contains what the system will be able to do and how it will be done. This should include:
 * The costs of building, testing and running the system (including both hardware and software)
 * Estimated time till completion
 * List of hardware and software tools needed
 * Description of hardware and software functions
 * Performance of the system
 * List of personnel and allocated tasks

Feasibility Report
A feasibility report can be produced during the analysis, design stage, or both. It should include:
 * Cost
 * Expected benefits
 * Time period
 * Potential difficulties

Alternative Solutions
There are a number of different ways a problem can be solved, with or without using a computer. One consideration you must take into account is the input and output of the solutions. The software itself could be one of three types:
 * General Application Software - This is the least expensive solution but may not include all the features that the user requires. A typical example would be an office package.
 * Specific Applications Packages - These are typically more expensive then general application software and provide a greater number of features. These programs tend to have been written specifically for business.
 * Tailor Made Software - This is the most expensive option but can be customized to do exactly what the customer requires as it is written from scratch.

Methods Of Testing Systems
Systems usually go through several stages of testing. Alpha testing is the first stage in which asmall group of qualified individuals examine an early version of the program. Beta testing is when the program is fully featured an released to a wider audience for testing.

Test data is also used to make sure the program outputs the expected data. We can test the program with:
 * Normal Data - Data that is expected to be entered into the program. Including data at the limits of what is expected.
 * Extreme Data - This will be outside the normal limits of the program, simulating what happens if a user enters incorrect data by mistake.
 * Abnormal Data - Data that is not expected, for example a string instead of an integer value.

Methods Of Implementing New Systems
A new system can be implemented in one of the following three ways:
 * Parallel Running - This is when both new and old systems are run together. This confirms that they both produce the same outputs and if any faults occur they can be fixed with no up-time lost. Staff can be trained without fear of losing data, yet there may be twice as much work to do.
 * Phased Introduction - Parts of the system are implemented at different times, each part is then tested and confirmed, this means it will take much longer to implement.
 * Direct Changeover - Also known as a Big Bang, the old system is immediately replaced by the new one. Users need to be trained before the new system is implemented and there is a risk that it will not work correctly.

Importance Of Maintaining Systems
Proper maintenance of a system is essential; clear documentation to begin with helps this progress as programmers will not need to work hard to understand design decision if they are explained in documentation. This reduces the cost of maintenance. Periodic reviews and performance reviews use the same data collection techniques as seen in the analysis sections and indicate whether further improvements or modifications are needed.


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IB Computer Science/Science Systems Life Cycle and Software Development/System Analysis

Importance of Formulating A Problem Precisely
In order to create a good solution it is vital to understand what the problem is, so that the solutions are all focused towards it. There might be team of specialists that work on the problem; and all of them must be fully concerned about the issue. Furthermore the user of the system often knows the matter perfectly and he must be interviewed so that he can provide a good description of his requirements. There is also an economic concern, since the cost of the system is directly proportional to the benefits it will provide, all this information should then be written in a feasibility report. Lastly the most important thing of all; a system must be tested continuously to see if it satisfies all the requests, it is not possible to test a system without knowing what it was supposed to do.

Aspects In A Considered Problem
Various aspects are to be considered in finding a solution to a specific problem. This initial phase of analysis in systems can also be called fact finding. The reasons for this analysis are for the purpose of determining what aspects of the problem can be solved by computer means, what solutions have been used in the past to solve a similar problem, or what the costs may be in generating a new solution. Additionally information can be found such as how much time it may take to install a new system, and the responsibilities given to various persons in the development team.

All of the information that must be obtained, as described above, can be found through conducting interviews, or sending out questionnaires to employees in a company for example. The development team may also look up a history of the organization to see what information is available about the current system through existing documents. Research into other sources with different solutions to a similar problem and the observation of employees working under the existing system can also be investigated. Obviously, these methods of analysis are used at the development team's discretion, since they all have advantages and disadvantages (see topic 1.2.3 for more)

Outcomes
It is likely that after the analysis stage a number of possible solutions will be made. Therefore a decision will need to be made on which is the most suitable solution and whether it is worth making the change.

If the decision is to go ahead with the change a detailed plan must be produced, tasks must be allocated, and a feasibility report must be created.

Parts That Can Be Solved Using A Computer
Not all problems that can be solved with a computer are feasible or cost effective once both hardware and software constraints have been taken into account.

Three Basic Control Aspects
In general, the three basic control aspects of the system will be:
 * Input
 * Process
 * Output

Analysation By Modules
Modular decomposition breaks down the problem into smaller components. We usually find the modules deal with inputs, processes and outputs.


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IB Computer Science/Science Systems Life Cycle and Software Development/Systems Design

Parts Of A System
The main parts of any computer system follow the input-process-output model of data flow:

However, hardware also needs backing storage, as there is no permanent storage in the CPU:

Layers of software have also been implemented, so no direct contact with hardware is necessary:

Data in a System
When data is in a system it is often shown in flow diagrams with the following symbols:

Data Capture and Output Presentation

 * Data Capture
 * Manual Data Entry - Keyboard, mouse (Example: adding client records to a database)
 * Direct Data Entry - OCR/OMR scanners, barcode scanner etc (Example: Lending a book or locating borrower details)
 * Automatic Data Entry - Sensors (Example: automatic temperature control)

 * Data Presentation
 * Temporary Displays - VDU, LCD Display (Example: showing a price on a display)
 * Permanent Display - Printer (Example: a receipt)
 * Electrical/Mechanical Output - Actuator (Example: Sending credit card data from a bank to a cash machine)

Suitable Interface
The major two user interfaces are command line interfaces (CLI) and graphical user interfaces (GUI).

CLI's are much easier to implement and use less memory, however there is a much greater learning curve, yet long-term users may find them quicker than other interfaces.

GUI's are much more complex to implement and use more memory, they also require a mouse. Yet, icons make it easier to remember commands and these are grouped in menus. There is a much smaller learning curve. GUI's can also be referred to as 'WIMP' (Windows, Icons, Menus, Pointers)

System Flowchart
Usually X-shaped with inputs at the top of the X, processing in the middle and outputs at the bottom. Some of the shapes are parallelogram for input/output, trapezium for manual input, square for process, rectangle with curved bottom for document, and cylinder for disk storage.


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IB Computer Science/Science Systems Life Cycle and Software Development/Software Life Cycle

Major Stages
You should outline the major stages in the software life cycle. One model includes: system analysis, leading to a precise statement of the problem that needs solving (a requirements specification); software design; program construction, including testing and debugging; installation and operation; and maintenance. Other models are acceptable, as long as they emphasize the cyclical nature of the life cycle.

Cyclical nature of software production
Computers systems are used over long periods of time. The software in these systems requires periodic improvement. After the original design and implementation, further analysis, redesign and restructuring are required to accommodate changing needs. This will continue through many cycles of analysis, design, implementation and use.


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IB Computer Science/Science Systems Life Cycle and Software Development/Software Design

Modularity
Modularity is a concept that has applications in the contexts of computer science, particularly programming, as well as cognitive science in investigating the structure of mind. A module can be defined variously, but generally must be a component of a larger system, and operate within that system independently from the operations of the other components.

Modularity in Computer Gayence

Modularity is the property of computer programs that measures the extent to which they have been composed out of separate parts called modules. A modular approach to programming is gaining popularity in fields of artificial intelligence systems integration, where a large-scale general A.I. system is composed of modules that each serve a specific purpose and communicate with each other to produce the system's overall behavior. Programs that have many direct interrelationships between any two random parts of the program code are less modular than programs where those relationships occur mainly at well-defined interfaces between modules.

Prototyping
Prototyping is the process of quickly putting together a working model (a prototype) in order to test various aspects of a design, illustrate ideas or features and gather early user feedback. Prototyping is often treated as an integral part of the system design process, where it is believed to reduce project risk and cost. Often one or more prototypes are made in a process of incremental development where each prototype is influenced by the performance of previous designs, in this way problems or deficiencies in design can be corrected. When the prototype is sufficiently refined and meets the functionality, robustness, manufacturability and other design goals, the product is ready for production.

see prototyping for a more detailed explanation

End Users
The end user is a popular concept in software engineering, referring to an abstraction of the group of persons who will ultimately operate a piece of software (i.e. the expected user or target-user). This abstraction is meant to be useful in the process of designing the user interface, and is therefore built on a relevant subset of any user's characteristics which may include which computer interfaces he/she is comfortable with (having used them before or because of their inherent simplicity), his/her technical expertise and degree of knowledge in specific fields or disciplines, and any other information which is believed to be relevant in a specific project. When little constraints are imposed on the end-user category, i.e. when writing/publishing programs for the general public, it is common practice to expect minimal technical expertise or previous training in the use of computer interfaces. This is also the general meaning associated with the term end user (see also Luser). In this context, intuitive GUIs (possibly with a touch interface) are usually preferred over more sophisticated command line interfaces for the sake of usability.

Efficiency
For Standard Level, only a qualitative treatment or a specific calculation of the efficiency is expected. "O" or BigO notation is required only at HL.

Debugging
Testing implies tracing sections of an algorithm, including responses to errors ("dry runs"), as well as the design of test cases, which are then executed. Students must be able to propose suitable test data, and give reasons. Debugging has the components of detecting, diagnosing and correcting errors shown up by testing.

Tools Of Debugging
Ideally, students should use an integrated development environment (IDE) combining an editor, interpreter or compiler and debugging tools, but this is not a requirement.


text:
IB Computer Science/Science Systems Life Cycle and Software Development/Documentation

Need Of Documentation
It will be very important that the documentation supplied with the original system is clear and complete. This documentation will be used to make it easier to design modifications to the system.

Features For User
It is required to write end-user instructions according to the standards described in the guidelines for the program dossier. Still, other user manuals may be needed (for example, on-line help systems and installations manuals where systems are installed by personnel other than end-users).


text: Telecommunications Theory/Hypodermic Needle Theory


text: Telecommunications Theory/Modeling and Social Cognitive Theory of Mass Communication


text: Telecommunications Theory/Limited Capacity Model of Motivated Mediated Message Processing


text: Telecommunications Theory/Cultivation

title: Telecommunications Theory/Cultivation


text: Telecommunications Theory/Constructions of Social Reality


text: User talk:135.245.8.35

title: User talk:135.245.8.35


text: Telecommunications Theory/Accessibility Theory


text: Telecommunications Theory/Media Dependency


text: User talk:78.175.219.110

title: User talk:78.175.219.110


text: Telecommunications Theory/Agenda Setting Framing Priming


text: Telecommunications Theory/3rd Person Effect


text: Telecommunications Theory/Uses and Gratifications


text:
Telecommunications Theory/Flow - Presence - Transportation Theory

Flow
Flow is a theoretical concept proposed by psychologist Mihály Csíkszentmihályi. It postulates that when difficulty of task is matched to the skill of the person doing it, a state of "flow" is reached. (citation needed)

Flow
(http://www.sciencedirect.com/science/article/B6VD0-4B0SWDC-1/2/94783dc82f5f015ee6105f60b05cc680)
 * Chin-Lung Hsu and Hsi-Peng Lu, Why do people play on-line games? An extended TAM with social influences and flow experience, Information & ManagementVolume 41, Issue 7,, September 2004, Pages 853-868.
 * Csíkszentmihályi, Mihály (1975). Beyond Boredom and Anxiety. Jossey-Bass: San Francisco, CA. 36. ISBN-10: 0875892612, ISBN-13: 978-0875892610
 * Csíkszentmihályi, Mihály (1990). Flow: The Psychology of Optimal Experience. New York: Harper and Row. ISBN 0-06-092043-2
 * Csíkszentmihályi, Mihály (1996). Creativity: Flow and the Psychology of Discovery and Invention. New York: Harper Perennial. ISBN 0-06-092820-4
 * Csíkszentmihályi, Mihály (1998). Finding Flow: The Psychology of Engagement With Everyday Life. Basic Books. ISBN 0-465-02411-4 (a popular exposition emphasizing technique)
 * Csíkszentmihályi, Mihály (2003). Good Business: Leadership, Flow, and the Making of Meaning. New York: Penguin Books. ISBN 0-14-200409-X
 * Jackson, Susan A. & Csíkszentmihályi, Mihály (1999). Flow in Sports: The Keys to Optimal Experiences and Performances. Champaign, Illinois: Human Kinetics Publishers. ISBN 0-88011-876-8
 * Sherry, J. L. (2004). Flow and media enjoyment. Communication Theory, 14(4), 328-347.

Presence

 * Kwan Min Lee (2004) Presence, Explicated Communication Theory 14 (1), 27–50 doi:10.1111/j.1468-2885.2004.tb00302.x

Transportation

 * Green, M., Brock, T., and Kaufman, G. 2004. Understanding media enjoyment: The role of transportation into narrative worlds. Communication Theory 14, 4 (2004), 311-327.


text: Telecommunications Theory/Diffusion and Gap Theories


text: Wikijunior talk:Famous Inventors/Inventors in Communication/Nikola Tesla