[edit]
A Glossary of Computer Terminology
- bit
- A bit is the smallest amount unit of information. A bit stores one of two possible values. The prefix bi- implies two values (binary, bicycle, bisexual, etc ). By combining multiple bits together, larger values can be represented. For example, with two bits, four values can be represented, 00, 01, 10, 11. In general, with n bits, 2^n (2x2x...x2, with n 2's) different values can be represented.
- byte
- A byte is a group of eight bits. With eight bits you can represent 2^8 = 256 values. A byte is the basic unit of data on most computers. Most volumes of data are measured in bytes (kilo-bytes, mega-bytes, giga-bytes...).
- By adding a prefix to the basic unit, the byte, you can create a new unit. These prefixes refer to powers of two. Generally with a exponent that is a multiple of 10. For example, a kibi-byte is 2^10 (1024) bytes. Note that people will often use the metric prefixes (kilo, mega, giga, tera) to mean the same value as the prefixes listed here. Technically these prefixes are powers of 10, not 2. Using the metric prefixes is far more common then the correct IEC prefixes.
- kibi-byte
- 2^10 (1024) bytes
- mebi-byte
- 2^20 (1048576) bytes
- gibi-byte
- 2^30 (1073741824) bytes
- tebi-byte
- 2^40 bytes
- CPU (Central Processing Unit)
- The CPU is the part of the computer that executes programs. For a more detailed description read these pages.
- word
- CPU's are designed to use a particular amount of data as a basic computing unit. Although most computers are able to work with other sizes of data, in general they are optimized to work with one particular size. Usually this is the size of a general purpose register in the CPU. For desktop computers, this size is generally 32 bits, (4 bytes). Other machines use 64 bits, some embedded computers use less 16, or even 8 bits. This size is refered to as the word size of the machine.
- address
- Imagine memory as a series of bytes layed out in a row. Each byte can be numbered from 0 to n. This number is refered to as the address of that byte of memory. Programs can use the address of memory to access the values stored in memory.
- virtual addressing
- Virtual addressing allows programs to use addresses that are not actual physical addresses. Instead the program stores addresses as values that can be mapped into physical addresses. In this way a program can be placed anywhere in memory while still being able to operate properly. This ability is necessary for computers to run multiple programs at the same time.
- pointer
- A pointer is used by a program to store an address. Pointers are used by software to access and refer to areas of memory.
- context switch
- A context switch saves the values stored in the CPU to memory and then loads another set of values into the CPU. By doing this a single CPU can run multiple programs. By making multiple context switches per second, a computer can seem to run multiple programs at once.