Units of Capacity

The capacity of memory (primary storage) and a storage device is expressed in numbers of bytes, which start with 1 and double: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, etc. For example, when a microcomputer system is listed with an "8 MB main memory," the computer has primary storage capacity of around 8 million bytes. The capacity of disk, tape and memory is measured in bytes, whereas that of the CPU and memory chips is measured in bits.

• Kilobyte (KB): About 1000 bytes (precisely, 1024 bytes). A kilobyte is abbreviated KB or K-byte.

• Megabyte (MB): About 1 million bytes. A megabyte is abbreviated MB or M-byte.

• Gigabyte (GB): About 1 billion bytes. A gigabyte is abbreviated GB or G-byte. Today's high capacity microcomputer has around 1 GB hard disk space.

• Terabyte (TB): About 1 trillion bytes. A terabyte is abbreviated TB or T-byte. This is a measure used with mainframe computers and supercomputers.