Units of Memory

Units of Memory

Bits – basic units of memory
Information is processed and stored in computers as electrical signals.A computer contains thousands of electronic circuits connected by switches that can only be in one of two possible states: ON (the current is flowing through the wire) or OFF (the current is not flowing through the wire). To represent these two conditions, we use binary
notation in which 1 means ON and 0 means OFF. This is the only way a computer can “understand” anything. Everything about computers is based on this binary process. Each 1 or 0 is called a binary digit or bit (binary + digit → bit).

Bytes and Characters
1s and 0s are grouped into eight-digit codes that represent characters (letters, numbers, and symbols). Eight bits together are called a byte. Thus, each character in a keyboard has its own arrangement of eight bits. For example, 01000001 for the letter A, 01000010 for B, and 01000011 for C.



The ASCII Code
Most computers use a standard system for the binary representation of characters. This is the American Standard Code for Information Interchange, known as ASCII (pronounced /×ski:/ “ask-key”). There are 256 different ways of combining 0 and 1 bits in a byte. So they can give us 256 different signals. However, the ASCII code only uses 128 codes to represent characters. The rest of the codes are used for other purposes. What makes this system powerful is that these codes are standard.


Kilobytes, Megabytes, and Gigabytes
In order to avoid astronomical figures and sums in the calculation of bytes, we use units such as kilobytes, megabytes, and gigabytes. One kilobyte is 1,024 bytes (210) and it is represented as KB, or more informally as K. One megabyte is equivalent to 1,024 KB, and one gigabyte is 1,024 MB. We use these units (KB, MB, GB) to describe the RAM memory, the storage capacity of disks, and the size of any document.