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Coding - Decoding

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In coding, particular code or pattern is used to express a word in English language as a different word. The coded word itself does not make any sense unless we know the code or the pattern that has been followed. Decoding is the process of arriving at the equivalent English word from the code word given. Coding/Decoding questions test the ability of a student to identify hidden patterns and judge his/her intelligence and mental ability.

These questions can be broadly classified into 4 main categories, as follows :

  • Alphabetical coding
  • Numerical Coding
  • Mixed Coding (Alpha-numeric)
  • Coding with Arbitrary Signs / Symbols

 Alphabetical Coding

In these questions, the letters of the alphabets are exclusively used. These letters do not stand for themselves but are allotted some artificial values based on some logical patterns/analogies. By applying those principles or observing the pattern involved, one has to decode a coded word or encode a word. These can be further classified into the following categories :

i. Simple Analogical Letter Coding

These are also called arbitrary codes. There are 2 definite principles/pattern involved. Codes are based on the analogy of one example from which different codes are to be formed.

ii. Letter Coding on Specific Pattern

In such questions, letters of alphabets are no doubt allotted artificial values but based on certain specific pattern/principles. One has to first observe the specific pattern involved and then proceed with coding or decoding depending on the question type.

Numerical Coding

The pattern of coding with numerical digits is similar to that of coding with alphabets except for the use of numerical digits with the assignment of some artificial values. The values are allotted based on some specific pattern which has to be discerned by the candidate in order to solve the problem in the quickest possible time.

i.Analogical Coding with Numerical Digits

Analogical coding with numerical digits involves the method of coding where the letters of alphabets are allotted numerical values and the pattern of coding is based on the analogy of the example given in the question. There are no set of principles or patterns involved.

ii.Coding with Specific Pattern

This is the pattern of coding which exhibits the natural correlation of Arabic numbers with alphabetic letters. For instance, alphabets A to Z are assigned the numeric codes from 1 to 26 where each letter gets the assignment in the pattern as follow A = 1, B = 2, C = 3, etc.

The sequence is classified as follows : Forward sequence (e.g. A = 1, B = 2, etc.)

Backward sequence (e.g. Z = 1, Y = 2, A = 26, etc.)

Random Sequence (e.g. A = 2, B = 3 or A = 4, B = 6, C = 8 or any other pattern following a particular sequence)

a. Forward Sequence:

Ex : If ‘PACE’ is code as 16-1-3-5, how will you code ACTED?

Sol: 1-3-20-5-4

b. Backward Sequence:

Ex: If GREAT is coded as 20-9-22-26-7, how will you code GATE?

Sol: 20-26-7-22

c. Random sequence:

The sequence will not follow a specific pattern of assignment as in other cases but will surely show a pattern at a strict analysis. The pattern can be established by various ways but in every case a set principle/pattern is involved which has to be discovered by careful examination of the example given in the question.

Ex: If FRANCE is coded 9-21-4-6-8, code INDIA after discerning the principle/ pattern involved.

Sol: The pattern of assignment can be determined to be as follows

A

B

C

D

E

F

G

H

I

J

K

L

M

4

5

6

7

8

9

10

11

12

13

14

15

16

 

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

17

18

19

20

21

22

23

24

25

26

1

2

3

 Based on above pattern, the answer is 12-17-7-12-4

Mixed Coding (Alpha-Numeric)

Mixed coding takes the pattern of coding with both the letters of alphabets and numerical assignment.

Ex: If “A – 3 – T – 5 – D” stands for ACTED and “D1T5D” stands for “DATED”, how is FADED coded?

Sol: F1D5D

Coding with Arbitrary Signs / Symbols

The pattern of coding here takes an extensive use of arbitrary signs and symbols. A careful deciphering of the codes is required to decode the question series.


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