## Revision

This is revision for the end of year examination in computer science.

Just because there is a topic here does not mean that it will be in the examination.

Similarly, if there is a topic that is not mentioned then that does not mean that it will not be examined.

## Logic

You are expected to know these three logic gates, what are they called and what do they do?

You will need to be able to draw a "truth table" for each logic gate ...

Truth tables for AND, OR and NOT
AND   OR   NOT
X Y X AND Y   X Y X OR Y   X NOT X
0 0 0   0 0 0   0 1
0 1 0   0 1 1   1 0
1 0 0   1 0 1
1 1 1   1 1 1

... and be able to both draw and evaluate circuits for situations provided by the examiner.

Important note: take care with drawing these logic gates, if you draw quite scruffily and the examiner cannot distinguish which gate is which then he will not gues correctly - if you give the examiner a choice he will always take the wrong answer.

Example: there is a light controlled by a switch and a sensor that is used to detect movement and a sensor that detects the lack of sunlight so that the switch will turn the light on but even if the switch is off and it is dark and there is movement then the light comes on. Show that the diagram below is the answer.

Question: there is a light in a passageway with two switches, one at each end, create a circuit so that changing the switch position on either switch will turn the light on if it is off and off if it is on.

## Glossary

algorithm A sequence of logical instructions for carrying out a task. In computing, algorithms are needed to design computer programs. Arithmetic logic unit - a component of the CPU that performs calculating functions such as addition and subtraction. A number system that contains two digits, 0 and 1. Also known as base 2. The smallest unit of data in computing represented by a 1 in binary. A data type in computing which only has two possible values, true or false. Central processing unit - the brain of the computer that processes program instructions. Also called a microprocessor. In computer programming, data is divided up and organised according to type, eg numbers, characters and Boolean. Any piece of computing hardware. The process of a program being run on a computer. Circuit components which take several inputs, compare the inputs with each other, and provide a single output based on logical functions such as AND, OR and NOT. An overflow error is caused when the processor does not have enough bytes available to process an instruction. A language used by a programmer to write a piece of software. There are many programming languages. A method of writing up a set of instructions for a computer program using plain English. This is a good way of planning a program before coding. The smallest element of a programming language which expresses an action to be carried out. Microscopic devices that open and close circuits to communicate electrical signals. CPUs contain millions of transistors. Used to assess possible results of a Boolean algebra statement. In a computer program, this is a memory location where values are stored.

## Questions

These are questions that relate to the AQA guides above.

## Revision

These are some revision topics and example questions that will aid revision for the year 10 examination on 23rd June 2017. Just because it is in this list does not mean that its in the exam and if it is not in the list it does not mean that the topic is not inthe exam.

## Mock examination

Here are the answers to the mock examination that you took in the summer.

For many students the objective here is to understand how to answer questions, to see where silly mistakes were made that cost easy marks and to appreciate how the examiner can aske questions relating to the theory that you already know.

## Coursework

Here is the information regarding your coursework as well as some worked examples to show you how coursework should be written up.

The coursework will be done twice, once with the example task for practice and then the real NEA task. You will only have 20 hours in which to complete the real task; there cannot be any extra time given.