The concept that will be discussed, applicable to all computers, including the IBM PC, PS/2, and compatibles. One of the most important features of a computer is how much memory is has. Bit is a binary digit that can have the value 0 or 1. A Byte is defined as 8 bits. A nibble is a half byte, or 4 bits. A word is two bytes, or 16 bits. The display is intended to show the relative size of these units, they could all be composed of any combination is zeros and ones.


Bit       0
Nibble       0000
Byte     0000 0000
Word 0000 0000 0000 0000


A Kilobyte is 210 bytes, which is 1024 bytes. The abbreviation K is often used to represent kilobytes. e.g; some Floppy disks hold 356K of data. A megabyte, it 220 bytes, which is over 1 million bytes; it is exactly 1,048,576 bytes. A gigabytes is 230 bytes, which is over 1 billion bytes, and terabytes is 240, which is over 1 trillion bytes.

How these some on terms are used in computers, suppose that a given computer has 16 megabytes of memory. That would be 16 X 2020, or 24 X 220, which is 224. Therefore 16 megabytes is 224 bytes.

Two types of memory commonly used in microcomputers are RAM, which stands for "random access memory", sometimes called Read/Write memory. ROM stands for "read only memory", RAM is used by the computer for temporary storage of programs that it is running. That data is lost when the computer is turned OFF. RAM is sometimes called volatile memory. ROM contains programs and information essential to operation of the computer. The information in ROM is permanent, cannot be changes by the user, and is not lost when the power is turned OFF. Therefore, it is called nonvolatile memory.



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