Learnearn.uk » IGCSE Computer Science Course » Units and file sizes

# Units and file sizes

## File Sizes

### Talking about file sizes – BYTES

 Bytes – File Sizes, Memory Sizes Nibble 4 bits (Only need to know this for the exam) Byte B 8 bits Kilobyte KB 1000 Bytes Megabyte MB 1000 Kilobytes 1,000,000 Bytes Gigabyte GB 1000 Megabytes 1,000,000,000 Bytes Terabyte TB 1000 Terabytes 1,000,000,000,000 Bytes

When we are talking about file sizes we usually use Bytes as our basic unit.

For a example:

• A text file is 25KB
• A photo is 4.5MB
• A computer game is 234GB

We use the same metric system as in normal maths – kilo, mega, giga, etc with each being 1000 times large than the previous one.

If you converting from one unit of bytes to the next you just either times by 1000 or divide by 1000.

Example:

• 2MB = 2,000KB = 2,000,000 Bytes
• 1,450MB = 1.45GB

## Networking Speeds

 Bits – Network / Data Transfer Speeds bit b 1 bit Kilobit Kb 1000 Bits Megabit Mb 1000 Kilobits 1,000,000 bits Gigabit Gb 1000 Megabits 1,000,000,000 bits Terabit Tb 1000 Gigabits 1,000,000,000,000 bits Usually expressed as a speed E.g. 20Mb/s – 20 Megabits per second transfer speed

Most manufacturers talk about transmission speeds using bits not bytes

## Conversions

Converting from bits to bytes

If you want to convert from bits to bytes, you simply divide the number of bits by 8

64 bits = 8 bytes

Converting from bytes to bits

To convert from bytes to bits you simply multiply the number of bytes by 8

2,000 Bytes  = 16,000 Bits

## Crossword

1. 1000 Bytes
2. 1,000,000 Bits
3. 1,000,000 Kilobits
4. 1,000,000 Kilobytes
5. Used for storage and memory
6. Used for transmission speeds
7. Most appropriate unit for a smartphone photo
8. 1000 bits
9. 4 bits