A busy kitchen
Picture a busy kitchen. A cook makes the food. The cook works at a table. The food waits in a cupboard.
A computer works the same way. The CPU is the cook. The memory is the table. The storage is the cupboard. Let us look at each one.
Key words
| Word | What it means | Example |
|---|---|---|
| CPU | The processor. It runs the instructions of a program. | The cook |
| Core | One working part inside a processor. More cores can do more jobs at once. | Four cores |
| Clock speed | How many steps a processor makes each second. It is measured in GHz. 1 GHz is 1 billion (1,000,000,000) steps each second. | 3 GHz |
| Cache | A very small, very fast memory inside or next to the processor. | The chopping board |
| RAM | Main memory. It holds the programs and data in use now. It is erased when the power goes off. | The table |
| ROM | Read-only memory. It keeps its contents with no power. It holds start-up instructions. | The recipe on the wall |
| Secondary storage | Storage that keeps files for a long time, even with no power. | The cupboard |
| MB and GB | Sizes of data. MB is megabyte. GB is gigabyte. 1 GB is 1000 MB. | A song is 4 MB |
| Firmware | Small programs stored on a chip inside a device. They start the device. | The start-up program |
The cells students fill in are left blank in this preview.
The processor: three numbers
Three numbers describe a processor.
The number of cores: each core can work on its own job. Two cores can do two jobs at once.
The clock speed: how fast each core works. A bigger number is faster, but only when the other numbers are the same.
The cache size: more cache means the processor waits less for data.
Compare two processors
| Processor A | Processor B | |
|---|---|---|
| Cores | 2 | 8 |
| Clock speed | 3.5 GHz | 3.0 GHz |
| Cache | 4 MB | 16 MB |
| Good for | One program that needs speed | Many programs at once, such as video editing |
The cells students fill in are left blank in this preview.
Quick check: the processor
Have a go
Quick check: the processor
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Mobile processors
A phone cannot have a big fan or a big battery. So a mobile processor is built to use little power and make little heat.
This saves space and battery.
RAM and ROM
| RAM | ROM | |
|---|---|---|
| What it holds | Programs and data in use now | Firmware: the start-up instructions |
| Power off | Everything is lost | Everything is kept |
| Can you change it? | Yes, all the time | No, or only with special steps |
| Size in a laptop | Large, for example 16 GB | Very small |
The cells students fill in are left blank in this preview.
Secondary storage: three kinds
RAM is erased when you switch off. Your photos and homework must stay. So a computer also has secondary storage.
Magnetic storage is a hard disk. A spinning disk holds the data. It is cheap but slow and it can break if dropped.
Solid state storage (an SSD) has no moving parts. It is fast and quiet. It costs more for each gigabyte.
Optical storage is a CD or a DVD. A laser reads the disc. It is cheap and easy to post, but it is slow and small.