1.3

A set of instructions designed to solve a problem

A name given to an element of a program so it can be referred to throughout

• Meaningful names, clear what variable is holding • Annotation, easier for programmers to follow • Program Layout, see each function and aids readability

An attribute within a program whose value can be reassigned (during execution)

An attribute within a program which never changes its value (during execution)

• Declared at the top of the program • Available to the whole program

• Declared inside a subroutine • Available only to that subroutine

Steps processed once

• Uses a logical condition to determine which line of code to process next • Purpose: to execute code if a certain condition is met

When another selection statement is contained within an existing selection statement

Purpose: to repeatedly execute code until a certain condition is met

A value in a loop that will increase/decrease each time the loop is executed

a value which tells the computer that input has finished

// How many times one number goes into another

% Remainder after DIV

• Cannot be decompressed to yield back the original data • Not Good method for critical data such as text • Good for digitally sampled analogue data e.g. Sound/Video/Graphics • Algorithms vary but many use threshold truncation

• Original message can be decompressed back to it’s original form • Good for text • Good for high quality media e.g. .FLAC .PNG

Finding frequently occurring character combinations and replace them with tokens

Replace long strings with a number

Approximate all shades of blue in a photograph to one shade and only store this colour instead of every pixel

• Algorithms and programs can be broken down into smaller parts. • These are named, reusable pieces of code that can be called any number of times within an algorithm to perform a specific task.

• Can be developed by teams, easier to write. • Code is more readable • Avoids duplication of code. • Sections can be tested individually.

STANDARD FUNCTION Carries out a common task for a standard situation in a program and is provided by the compiler/interpreter STANDARD MODULE Contains a group of related standard functions EG: Module = math Function = math.cos(x)

• Pre-written / No need to write again (Saves Development Time) • High Quality as written by experts • Already Tested/Used – Less Errors