Understanding Computers: Unit Exam A
The CPU, RAM and storage, binary and denary, bits, bytes and the units of storage, pixels, sound samples and character sets.
Instructions
- Time allowed
- 25 minutes
- Total marks
- 25
- Calculator
- No calculator is permitted.
- Answer all the questions.
- The number of marks for each question is shown in brackets. Use it as a guide to how much to write.
- The clock at the top counts down from the real time allowed. When it reaches zero the paper is locked and marked, as it would be collected in the exam hall.
- Read every question to the end before answering. Where a question says tick two boxes, tick exactly two: ticking more than asked scores nothing. Type one word and number answers carefully, because they are marked exactly.
Questions
Answer every question, then finish the paper to have it marked. Marking as you go teaches you far less.
Tick one box.
- LC Central Processing Unit
CPU stands for Central Processing Unit.
Tick one box.
- LA To fetch and carry out instructions
The CPU fetches instructions from memory and carries them out.
| RAM | Hard disk drive | |
|---|---|---|
| Loses its contents when the power is turned off | ||
| Keeps files when the computer is switched off | ||
| Holds the programs that are running right now | ||
| Usually has a much larger capacity |
Tick one box in each row.
- LLoses its contents when the power is turned off: RAM
- LKeeps files when the computer is switched off: Hard disk drive
- LHolds the programs that are running right now: RAM
- LUsually has a much larger capacity: Hard disk drive
RAM is volatile working memory for running programs. A hard disk drive is permanent storage with a large capacity.
- L5
- L10
- L25
101 is 4 + 1 = 5. 1010 is 8 + 2 = 10. 0001 1001 is 16 + 8 + 1 = 25.
- L0110
6 = 4 + 2, so the 4 and 2 columns are 1: 0110.
- L8
A byte is 8 bits.
- L15
1111 = 8 + 4 + 2 + 1 = 15.
- L1000 bytes
- L1000 kilobytes
- L1000 megabytes
Each unit is 1000 times the one before (1024 in the older binary convention, which is also accepted).
Tick one box.
- LD Because their circuits have two states, on and off
Transistors are either on or off, which maps exactly onto 1 and 0.
Tick one box.
- LB The smallest dot of colour in an image
An image is a grid of pixels, each one a single colour.
Tick one box.
- LA A list of characters and the binary code that represents each one
A character set such as ASCII gives every character a number, stored in binary.
- LPrograms that are open, and their data, are held in RAM
- LMore RAM means more fits at once, so the computer does not have to use slower storage instead
Every open program and its data are held in RAM while they run. With more RAM, more programs fit at the same time, so the computer does not have to move data out to much slower storage, which is what makes it slow down.
Tick one box.
- LC 1 GB
1 GB is 1000 MB, larger than 800 MB.
- Lsample
Each measurement is a sample. The number taken each second is the sample rate.
Tick two boxes.
- LA USB flash drive
- LC Solid state drive
- LNo marks if more than 2 boxes are ticked
Secondary storage keeps data permanently: flash drives and solid state drives.
- L4
00, 01, 10 and 11: four patterns.
This is an original Key Stage 3 assessment. Most questions are closed, so the marking is exact, and the written answers are marked against a mark scheme in the same style as a GCSE paper, so the format is familiar long before it counts.