Computer Science GCSE

System Clock

Makes sure everything is in sync

Control Unit

Directs other CPU components to execute an instruction

Arithmetic Logic Unit

Carries out Arithmetic and Logic calculations

Registers

Very fast access, small storage near the processor

Cache

Stores frequently used instruction

Buses

Carries data between componenets

Program counter

Holds the address of the next instruction. Increases by 1 increment every FDE cycle.

Memory Address Register

Holds the address of the instruction

Memory Data Register

Holds the data being processed

Step one FDE

Address is copied from programme counter to MAR.

Step two FDE

CPU fetches instruction from memory; imports necessary data and stores it in the MDR

Step three FDE

Control unit decodes the instruction, and carries out the instruction.

Primary Storage

Volatile data being used by the processor

Secondary storage

Long term data non-volatile storage for programmes and OS

Tertiary storage

Backup data storage in large quantities (eg. Data centers)

RAM

Random Access Memory, Volatile primary storage

ROM

Read only memory, Non volatile primary storage

What is a character set

A set of unique binary codes which represent specific characters

ASCII number of bits

7

ASCII extended number of bits

8

Unicode number of bits

Up to 32

Color depth

The number of bits per pixel

Left shift in binary meaning

Multiplying by 2^number of points moved

Right shift in binary meaning

Dividing by 2^number of points moved

Algorithm

A set of rules that are used to solve a problem

Computational Thinking

A set of techniques used to solve problems

Decomposition

When you break down a complex problem into smaller, simpler problems

Pattern Recognition

Recognising patterns in problems, in order to solve the bigger problem

Abstraction

Focusing on important details and discarding unnecessary information to solve a problem

Algorithm Design

Working out the steps of a problem to solve it

Interpreter

Converts programme to binary line by line

Compiler

Converts programme to binary in one go

Functions of IDE

Edit, Debug, Translate, document

Function of a operating system

User interface, Multitasking, running applications

Function of Utility software

Maintains and optimizes the computer

Purpose of GUI

Allows the user to interact with computer in a visual way

Purpose of Command line interface

Allows user to interact only with typed commands

How does Disk Defragmentation work

Moves files so parts of files are stored together

How does a disk become fragmented

Parts of files are moved around, so that they are not together

Device driver

Software that allows for OS and hardware to connect

Embedded system

A computer system inside another device