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Other binary codes

03-02-19 Mounika Mayakuntla 0 comment

Other binary codes:

                   Other binary codes for decimal numbers and alphanumeric characters are sometimes used. Digital computers also employ other binary codes for special applications. A few additional binary codes encountered in digital computers are presented in this section.

Gray codes: It is a binary code used for encoding shift position data from machines such as computer controlled lathes. The data must be converted into digital form before they can be used by a digital computer. Continuous, or analog, information is converted into digital form by means of an analog-to-digital converter. The advantage of gray code over straight binary numbers is that the gray code changes by only one bit as it sequences from one number to the next. In other words, the change from any number to the next in sequence is recognized by a change of only one bit from 0 to 1 or from 1 to 0.

                   Gray code counters are sometimes used to provide the timing sequences that control the operations in a digital system. A gray code counters remove the ambiguity during the change from one state of counter to the next because only one bit can change during the state transition.

Other Decimal Codes: Binary codes for decimal digits require a minimum of four bits. Numerous different codes can be formulated by arranging four or more bits in 10 distinct possible combinations.

          The Binary coded decimal ( BCD ) has been introduced before. It uses a straight assignment of the binary equivalent of the digit.  One disadvantage of using BCD is the difficulty encountered when the 9’s complement of the number is to be computed.

Other Alphanumeric Codes:  The ASCII (American Standard Code for Information Interchange) code is the standard code commonly used for the transmission of binary information. Each character is represented by a 7-bit code and usually an eighth bit is inserted for parity. The code consists of 128 characters. 95 characters represent graphic symbols that include upper and lower case letters, numerals 0-9, punctuation marks, and special symbols. 23 characters represent format effectors, which are functional characters for controlling the layout of printing or display devices such as carriage return, line feed, horizontal tabulation and back space.  The other 10 characters are used to direct the data communication flow and report it’s status.

          When alphanumeric characters are used internally in a computer for data processing it is more convenient to use a 6-bit code to represent 64-characters. A 6-bit code can specify the 26 upper case letters of the alphabet, numerals 0-9 and upto 28 special characters. This set of characters is usually sufficient for data processing purposes. Using fewer bots to code characters has the advantage of reducing the memory space needed to store large quantities of alphanumeric data.

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