subject: COMPUTER MEMORY [print this page] Computer memory is a device that stores data being use by the processor when processing and saving information. The memory read data in form of binary number machine language. Numbers are categories in terms of sequence digit 0 and 1 known as bits which represent the on and off state of computer system.
The bits are always grouped together in order to represent larger values within the memory. A set of eight bits is called a byte which can represent decimal value ranging from 0 to 255. The particular sequence of bits in the byte encodes a unit of information, such as a keyboard character. One byte typically represents a single character such as a number, letter, or symbol. Most computers operate by manipulating groups of 2, 4, or 8 bytes called words.
The capacity of memory is usually measure in terms of kilobytes, megabytes, gigabytes and terabytes. The prefix kilo, mega and giga are goten from metric system, they have a slightly different meaning when applied to computer memories.
Computer memory may be divided into two broad categories known as internal memory and external memory.
INTERNAL MEMORY
Internal memory which is also known as random access memory (RAM) or read-only memory (ROM) operates at the highest speed and can be accessed directly by the central processing unit (CPU)the main electronic circuitry within a computer that processes information. The RAM stores information in volatile form, meaning it lost it data whenever there is power outage in the system while information stored in ROM may also be randomly access, in that it may be accessed in any order, but the information recorded on ROM is usually permanent and cannot be erased or written over. Internal memory is also contained on computer chips and uses electronic circuits to store information (see Microprocessor).
EXTERNAL MEMORY
On the other hand external memory consists of storage on peripheral devices that are slower than internal memories but offer lower cost and the ability to hold data after the computer's power has been turned off. External memory uses inexpensive mass-storage devices such as magnetic hard disk drives, floppy disk drive, tape drive, flash drive and also optical disk drive the cd-rom
