Year 8 Computer Science · KPI Revision

01

Binary & Number Systems

Computers only understand 0 and 1. Everything you see — pictures, music, this webpage — is made from these two numbers.

What is binary?

Humans count using 10 digits (0–9). This is called denary (base 10). Computers count using only 2 digits: 0 and 1. This is called binary (base 2). Each 0 or 1 is called a bit.

In binary, each column is worth double the column to its right. To convert binary to denary, add up the column values where there is a 1.

Binary addition

Binary addition uses 4 simple rules:

0 + 0 = 0
0 + 1 = 1
1 + 1 = 10 (write 0, carry 1)
1 + 1 + 1 = 11 (write 1, carry 1)

Binary shifting

Shifting is a fast way to multiply or divide by 2.

Shift LEFT by 1 place → multiply by 2
Shift RIGHT by 1 place → divide by 2
Shifting left by 2 places multiplies by 4. By 3 places multiplies by 8.

02

Introduction to Databases

A database is an organised collection of information stored on a computer so it can be searched and updated quickly.

Why use databases?

Imagine your school had to keep every pupil's information on paper. Finding one student would take ages! Databases store data in a structured way so a computer can find anything in milliseconds.

Key words to remember

Table — where the data is stored, like a spreadsheet
Record — one row in a table (e.g. one student)
Field — one column in a table (e.g. "Last Name")
Primary key — a field that is unique for every record (e.g. Student ID)
Query — a question you ask the database to get specific data

03

Computer Hardware

Hardware is the physical parts of a computer — anything you can touch.

The main parts

CPU (Central Processing Unit) — the "brain". It does all the calculations and instructions. Think of it as the chef in a kitchen.
RAM (Random Access Memory) — short-term memory. Holds programs you are using right now. Loses everything when the power is off!
Hard drive / SSD — long-term storage. Keeps your files even when the computer is turned off.
Motherboard — the big circuit board everything plugs into. It connects all the parts together.
GPU (Graphics Processing Unit) — handles pictures, videos and games.
Input devices — let you put data IN (keyboard, mouse, microphone)
Output devices — let the computer give data OUT (monitor, speakers, printer)

04

Algorithms & Flowcharts

An algorithm is a set of step-by-step instructions to solve a problem. A recipe is an algorithm!

The 3 building blocks

Sequence — doing things in order, one after another
Selection — making a decision (IF something is true, do this)
Iteration — repeating steps (a loop)

Flowchart shapes

A simple example

Algorithm to make a cup of tea:

Boil the kettle (sequence)
Put a teabag in the cup (sequence)
Pour the water in (sequence)
IF you like sugar, add 1 spoon (selection)
Stir until mixed (iteration — keep stirring!)

05

Networks & The Internet

A network is two or more computers connected together so they can share data.

Two types of network

LAN (Local Area Network) — covers a small area like your school or home
WAN (Wide Area Network) — covers a large area, even the whole world. The Internet is the biggest WAN!

Important words

Server — a powerful computer that gives services (like web pages) to other computers
Client — a computer that asks the server for things (your phone or laptop)
Router — sends data to the right place on a network
The Internet — the global network of networks
WWW — websites you visit using a browser. The Internet and the WWW are NOT the same thing!