Coding and Decoding

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Logical Reasoning: Coding and Decoding

Coding is a system of letters, digits and signs used for identification purposes. Codes are used for transmitting messages to the receiver without any third person knowing it.

The coding and Decoding questions set to judge the candidate's ability to perceive the principles and pattern on which a word or message is codified and to decipher it. Such questions of reasoning are becoming increasingly popular in the competitive examinations. They call for careful observation concentration, and analytical aptitude.

Types of Coding:

There are several types of coding based on their form, design and material.

Letter Coding

Capital letters are used to codify other capital letters.


TUBS is used to denote STAR.

Small letters are used to codify a word.


SCHEME is coded as rbgdld.

Letters and Numeral Coding

Letters in a word are coded as numeral.


SPACE is coded as 96312.

Numerals way is represented by letters.


238 signify SKY.

Signs and Symbols Coding

Signs, Symbols and characters are used as codes.

Matrix Coding

Matrices having vertical columns and horizontal rows each marked from 0 to 9 are given. Each cell contains one letter in it. The respective position of the letter in the column as well as row determines its value.

In matrix coding two types of matrices can be used. In type one, two matrices i.e. Matrix1 and Matrix11 are used. Matrix has five vertical columns marked 0 to 4 and five horizontal rows also marked 0 to 4. Five letters appear in each column and row which are same but in different order. In Matrix11 there are five vertical columns marked 5 to 9 and five horizontal rows also marked 5-9. Five letters appear in different order.

Each letter from the matrix can be represented first by its row and next by column number. For example in Mtrix i below, the letter D is represented by 04, 14, 20, 3 or 43. In Matrix ii the letter B is represented by 56, 66, 75, 87 or 99.

Mixed Letter Coding

In this type of codes a word is denoted by a group of letter.


CROSS OVER is denoted by dsptt pwfs.

Mathematical Operations

Each letter is assigned a value. The code of a word may be the sum of values of all of its letters.


If 1234567 is ECLIPSE, what would the number 63775 denote?

Ans: 63775 = SLEEP

Because, the code is 6 = S, 3 = L, 7 = E, 5 = P

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