Informatics Practices · Ch 1 — Computer System
Units of Memory
Units of Memory
Everything a computer stores or processes — numbers, text, pictures, programs — is ultimately represented in binary. Understanding the units of memory therefore starts with the two binary digits themselves and builds upward to the enormous capacities of modern storage.
The binary digits 0 and 1 are called bits, and a bit is the basic unit of computer memory. Bits are rarely used alone; they are grouped together to form words.
Two small word sizes have their own names:
- A nibble is a 4-bit word. Examples: 1001, 1010, 0010.
- A byte is an 8-bit word — equivalently, a word made of two nibbles. Examples: 01000110, 01111100, 10000001.
Just as everyday units are scaled up into larger standard units, bytes are grouped together to make bigger chunks of memory. Each unit in the ladder below is 1024 times the one before it:
| Unit | Description | Unit | Description |
|---|---|---|---|
| KB (Kilobyte) | 1 KB = 1024 Bytes | PB (Petabyte) | 1 PB = 1024 TB |
| MB (Megabyte) | 1 MB = 1024 KB | EB (Exabyte) | 1 EB = 1024 PB |
| GB (Gigabyte) | 1 GB = 1024 MB | ZB (Zettabyte) | 1 ZB = 1024 EB |
| TB (Terabyte) | 1 TB = 1024 GB | YB (Yottabyte) | 1 YB = 1024 ZB |
To move along the ladder, remember one number: 1024. Reading the table across a full cycle — bytes, then KB, MB, GB, TB, PB, EB, ZB, YB — each step multiplies the capacity by 1024, so any unit can be converted to any other by repeated multiplication or division by 1024. …
| Unit | Description | Unit | Description |
|---|---|---|---|
| KB (Kilobyte) | 1 KB = 1024 Bytes | PB (Petabyte) | 1 PB = 1024 TB |
| MB (Megabyte) | 1 MB = 1024 KB | EB (Exabyte) | 1 EB = 1024 PB |
| GB (Gigabyte) | 1 GB = 1024 MB | ZB (Zettabyte) | 1 ZB = 1024 EB |