Computing gcse revision notes

Page 1

COMPUTING GCSE REVISION NOTES

Keywords:

Algorithm - A step-by-step series of instructions that describe how to complete a task

Assignment - When a variable is given a new value e.g. answer is being given a new value which is calculated by number1 and number2 together

Bit - A single 1 or 0, the smallest measure of a computer's memory

Network - A group of computers that have been connected together, so that they can share data or communicate

Computer System - Consists of hardware and software

Hardware - The physical components of a computer system

Software - The programs that run on a computer system

Subroutine - Is a procedure or function

Procedure - Is a chunk of program code

Function - Is a chunk of code that gives you an answer at the end

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Binary

128 | 64 | 32 | 16 | 8 | 4 | 2 | 1

57 would be 0 | 0 | 1 | 1 | 1 | 0 | 0 | 1

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Visual Basic Data Type

Description

Examples

Char

Used to store a single character

R

r

5

String

Used to store multiple characters

Bob

O’reilly

IG8 OTP

Integer

Used to store a whole number

9

45

-22

Single

Used to store a number with a fractional part

3.5

-1.235

4

Boolean

Used to store a true or false value only

True

False

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Units of measurements

A bit is a single one or 0

A group of 8 bits is called a byte

A group of 4 bits is called a nibble (half a byte)

A kilobyte is exactly 1024 bytes

A megabyte is exactly 1024 kilobytes

A gigabyte is exactly 1024 megabytes

A terabyte is exactly 1024 gigabytes

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

ASCII stands for : American Standard Code for Information Interchange

7 bits are used to represent an ASCII character

128 characters can be represented using ASCII- Not always enough because there's other languages, emoticons, mathematical symbols

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

32 bits are used to represent Unicode

4 billion characters can be represented using Unicode

The advantage of using Unicode over ASCII is that you can represent more characters

The disadvantage of Unicode to ASCII is it's less memory efficient

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Denary

Binary

Hexadecimal

0

0

0

1

0001

1

2

0010

2

3

0011

3

4

0100

4

5

0101

5

6

0110

6

7

0111

7

8

1000

8

9

1001

9

10

1010

A

11

1011

B

12

1100

C

13

1101

D

14

1110

E

15

1111

F

16

10000

10