Computer Science XI

Bits and Bytes

A numbering system is a way of representing numbers. The most commonly used numbering system is the decimal system. Computer systems can perform computations and transmit data thousands of times faster in binary form than they can use decimal representations. It is important for every one studying computers to know how the binary system and hexadecimal system work. A bit is small piece of data that is derived from the words “binary digit”. Bits have only two possible values, 0 and 1. A binary number contains a sequence of 0s
and 1s like 10111. A collection of 8 bits is called as a byte. With 8 bits in a byte, we can represent 256 values ranging from 0 to 255 as shown below: 0 = 0000 0000 1 = 0000 0001 2 = 0000 0010 3 = 0000 0011 ................. ................. ................. 254 = 1111 1110 255 = 1111 1111 Bytes are used to represent characters in a text. Different types of coding schemes are used to represent the character set and numbers. The most commonly used coding scheme is the American Standard Code for Information Interchange (ASCII). Each binary value between 0 and 127 is used to represent a specific character. The ASCII value for a blank character (blank space) is 32 and the ASCII value of numeric 0 is 48. The range of ASCII values for lower case alphabets is from 97 to 122 and the range of ASCII values for the upper case alphabets is 65 to 90. Computer memory is normally represented in terms of Kilobytes or Megabytes. In metric system, one Kilo represents 1000, that is, 103. In binary system, one Kilobyte represents 1024 bytes, that is, 210. The following table shows the representation of various memory sizes. Name Abbreviation Size (Bytes) Kilo Mega Giga Tera Peta Exa Zetta Yotta K M G T P E Z Y 2^10* 2^20 2^30 2^40 2^50 2^60 2^70 2^80 *Read as 2 power10.
In a 2GB (Gigabytes) storage device (hard disk), totally 21,47,483,648 bytes can be stored. Nowadays, databases having size in Terabytes are reported; Zetta and Yotta size databases are yet to come.

(Next Lesson) Hexadecimal Number System
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