Binary Codes - Computer Logical Organization

What are Binary Codes?

By encoding, an explicit group of symbols are used for representing a number or word or letter. Code implies to the explicit group of symbols. Binary code represents the stored and transmitted digital data. Numbers and alphanumeric letters are used for representing the Binary codes.

What are the advantages of Binary Code?

Some of the advantages offered by the binary code are as follows:

  • Computer applications mostly use Binary codes.
  • Digital communications mostly use Binary codes.
  • Digital circuits can be analyzed and designed by using the binary codes.
  • Implementation of binary codes is easy as only 0 and 1 are used.

How Binary codes are classified?

Binary codes are categorized into -

  • Weighted Codes
  • Non-Weighted Codes
  • Binary Coded Decimal Code
  • Alphanumeric Codes
  • Error Detecting Codes
  • Error Correcting Codes

What are Weighted Binary Codes?

When the positional weight balance principle is applied by the binary codes, they are known as Weighted Binary Codes. Explicit weight is represented by each position. A group of four bits represent a decimal digit in this Weighted Binary Code.

Weighted Code

What are Non-Weighted Binary Codes?

The positional weights are not assigned in Non-weighted Binary codes. Excess – 3 code and Gray code are illustrations of Non-weighted Binary codes.

Excess-3 code

The decimal numbers are expressed by a non-weighted code, known as Excess-3 code or XS-3 code. An example of Excess-3 code is as follows:

Excess 3 Code

Example

BCD Excess -3 Code

Gray Code

In this code, each time when a decimal number is incremented, only one bit is changed and hence is also called as unit distance code. Arithmetic operations cannot use Gray code as it being a cyclic code. The bit positions are not assigned with any specific weights.

Gray Code

Application of Gray code

  • Shaft position encoders widely use Gray code.
  • The angular position of the shaft is represented by the code word produced by the shaft position encoder.

What is Binary Coded Decimal (BCD) code?

Under this BCD code, a 4-bit binary number represents each of the decimal digit. BCD enables to represent 16 numbers by using 4 bits but BCD facilitates in using only the first 10 code combinations, while the rest are considered invalid.

BCD Code

Advantages of BCD Codes

  • It is very similar to decimal system.
  • The binary equivalent of decimal numbers from 0 to 9 is to be remembered.

Disadvantages of BCD Codes

  • There are different rules under BCD for addition and subtraction.
  • The BCD arithmetic is complicated.
  • The decimal numbers are represented by using more bits than binary and hence are considered less efficient than binary.

What are Alphanumeric codes?

Many more symbols apart from 0 and 1 are required for communication between two computers. These symbols should represent all the 26 alphabets (capital and small), all the numbers from 0 to 9 and punctuation marks.

The numbers and alphabetic characters are represented by alphanumeric codes. Symbols and other instructions used for communicating the information are also represented by the alphanumeric codes. The different alphanumeric codes that are most widely and commonly used for representing data are:

  • American Standard Code for Information Interchange (ASCII).
  • Extended Binary Coded Decimal Interchange Code (EBCDIC).
  • Five bit Baudot Code.

Among the three the most commonly used is ASCII which is a 7-bit code and EBCDIC is used for IBM computers which are huge and is an 8-bit code.

What are Error Codes?

The error in the data is detected and corrected during data transmission by the binary code techniques known as Error Detection and Correction.

Error Code
Description
Error Detection and Correction
Error detection and correction code techniques

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