by Dinesh Thakur
Category: BINARY CODE

Digital data is represented, stored and transmitted as groups of binary digits also known as binary code. The binary codes can be classified as shown in Fig.

Weighted codes: In weighted codes, each digit is assigned a specific weight according to its position. For example, in 8421BCD code, 1001 the weights of 1, 0, 0, 1 (from left to right) are 8, 4, 2 and 1 respectively.

Suppose W_{1}' W_{2}' W_{3} and W_{4} are the weights of binary digits and X_{l}' X_{2}, X_{3} and X_{4} are the corresponding digit values then decimal digit. N = W_{1} X_{l} + W_{2} X_{2} + W_{3} X_{3} + W_{4} X_{4} is represented by binary sequence X_{4} X_{3} X_{2} X_{4}.

The codes 8421BCD, 2421BCD, 5211BCD are all weighted codes.

• Non-weighted codes: The non-weighted codes are not positionally weighted. In other words, each digit position within the number is not assigned a fixed value ( or weight ).

Excess-3 and gray code are non-weighted codes.

• **Reflective codes**: A code is reflective when the code is self complementing. In other words, when the code for 9 is the complement the code for 0, 8 for 1, 7 for 2, 6 for 3 and 5 for 4.

2421BCD, 5421BCD and Excess-3 code are reflective codes.

• **Sequential codes**: In sequential codes, each succeeding 'code is one binary number greater than its preceding code. This property helps in manipulation of data.

8421 BCD and Excess-3 are sequential codes.

• **Alphanumeric codes**: Codes used to represent numbers, alphabetic characters, symbols and various instructions necessary for conveying intelligible information.

ASCII, EBCDIC, UNICODE are the most-commonly used alphanumeric codes.

• **Error defecting and correcting codes**: Codes which allow error defection and correction are called error detecting and' correcting codes. Hamming code is the mostly commonly used error detecting and correcting code.

About Dinesh Thakur

Dinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular Computer Notes blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.

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