Digital Electronics: Principles, Devices and Applications

2

Binary Codes

The present chapter is an extension of the previous chapter on number systems. In the previous chapter, beginning with some of the basic concepts common to all number systems and an outline on the familiar decimal number system, we went on to discuss the binary, the hexadecimal and the octal number systems. While the binary system of representation is the most extensively used one in digital systems, including computers, octal and hexadecimal number systems are commonly used for representing groups of binary digits. The binary coding system, called the straight binary code and discussed in the previous chapter, becomes very cumbersome to handle when used to represent larger decimal numbers. To overcome this shortcoming, and also to perform many other special functions, several binary codes have evolved over the years. Some of the better-known binary codes, including those used efficiently to represent numeric and alphanumeric data, and the codes used to perform special functions, such as detection and correction of errors, will be detailed in this chapter.

2.1 Binary Coded Decimal

The binary coded decimal (BCD) is a type of binary code used to represent a given decimal number in an equivalent binary form. BCD-to-decimal and decimal-to-BCD conversions are very easy and straightforward. It is also far less cumbersome an exercise to represent a given decimal number in an equivalent BCD code than to represent it in the equivalent straight binary form discussed in the ...