# Computer Science Revision (PAPER 2)

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- Created by: Kani.T
- Created on: 11-04-18 19:57

Bit Rate

The number of bits to store one second of sound

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Bit Rate Formula

Frequency x Bit Depth x Channels

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Machine Code instructions

Where an operator (op-code) tells the computer what to do (e.g. Load/Store); the operand tells the computer what to do with the instruction

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Nyquist's Theorem

The sample rate should be at a frequency which is at least twice the value of the highest frequency in the sampled signal

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Logic Gates

A logic gate is an elementary building block of a digital circuit

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NOT gate

This gate inverts the input and is represented by an overbar

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AND gate

Where the output of A AND B is 1 only if input A and input B are both 1

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OR gate

Where the input is always 1 unless both inputs are 0

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XOR gate

AKA: Exclusive OR- this is where the output is true if one or other input is true, but not both

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NAND gate

Inverts the output of an AND gate

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NOR

This gate only produces an output of true when both outputs are false

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De Morgan's First Law

NOT(A OR B) = NOT(A) AND NOT(B)

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De Morgan's Second Law

NOT(A AND B) = NOT(A) OR NOT(B)

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General Rules of Boolean Algebra

X.0 = 0 | X.1 = X | X.X= X | X.NOT(X) = 0 | X + 0= X | X+1= 1 | X+X= X | X+NOT(X)= 1 | NOT(NOT X)= X

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Commutative rules

X.Y = Y.X | X+Y= Y+X

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Associative rules

X. (Y.Z) = (X.Y) .Z | X+ (Y+Z) = (X+Y) +Z

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Absorption rules

A+ (A.B) = A | A. (A+B) = A

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Subroutine

A named block of code designed to carry out a specific task

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Procedure

Another term for a subroutine

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Local Variable

A variable that is only available in specified subroutines and functions

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Global Variable

A Variable that is declared at the beginning of the program and is available anywhere in the program

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Function

A subroutine that returns a value

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Functional Programming

A programming language that uses functions to create programs

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Parameter

Data being passed into a subroutine

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Arguement

An item of data being passed into a subroutine

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Exception Handling

The process of dealing with events that cause the current subroutine to stop

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Hierarchy Chart

A diagram that shows the design of a system from the top down

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Flowchart

A diagram that shows individual processes within a system

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Pseudocode

A method of writing code that does not require knowledge of particular programming language

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Laser scanners

How it works: reflects off a moving mirror which allows the barcode to be read in many different positions

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Radio Frequency Identification (RFID)

A chip that consists of a small microchip transponder and an antenna- used to track and identify things such as households products

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Laser Printer

Offers high-quality, high-speed printing; their function is similar to that of a photocopier using powdered ink called toner

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Hard Disk

Uses rigid rotating platters coated with magnetic material

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Optical Disk

Works by using a high powered laser to 'burn' sections of its surface, making them less reflective

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Solid-state Disk (SSD)

A storage device that uses integrated circuit assemblies as memory to store data persistently

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Cyber attack case study

In 2007, Estonia suffered a series of cyber attacks which swamped websites of organisations including the Estonian Parliament, banks, newspapers and broadcasters.

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Abstraction

A technique for arranging complexity of computer systems (simplifying it)

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Machine Code

A first generation language that only a computer can understand (1s and 0s)

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## Other cards in this set

### Card 2

#### Front

Frequency x Bit Depth x Channels

#### Back

Bit Rate Formula

### Card 3

#### Front

Where an operator (op-code) tells the computer what to do (e.g. Load/Store); the operand tells the computer what to do with the instruction

#### Back

### Card 4

#### Front

The sample rate should be at a frequency which is at least twice the value of the highest frequency in the sampled signal

#### Back

### Card 5

#### Front

A logic gate is an elementary building block of a digital circuit

#### Back

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