Published by: Divyanshu Nayak 
What is Coding-Decoding ?
Coding-Decoding Is a way to convey a message in a secret manner. This method hides the message from the third person and ensures the authenticity of the message between the sender and the receiver. Here, We have to understand the given pattern of the coded message and the reasoning based question on that pattern
In questions on Coding-Decoding, a word (basic word) is coded in a particular way and the candidates are asked to code other words in the same way. The coding and Decoding tests are set up to judge the candidate’s ability to decipher the rule that has bee followed to code a particular word/message
| Forward Order | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 |
| Alphabets | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| Backward Order | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
The Different Types of Coding-Decoding
- Coding Of Letters
- Coding of Numbers & Symbols
- Message Coding
- Coding By Substitution
- Miscellaneous
Type 1:- Coding of Letters
In this type of coding, The letters of a word are coded according to a certain pattern or rule to form other groups of letters. we have to Identify the pattern and answer the questions that are asked.
Before we begin, we have to memorize the position of all alphabets.
For easy understanding We can Just Remember the word “EJOTY“
This is the code that is derived on the basis of alphabets. usually, the position of alphabets is used. For example, let us see the following question.
Example 1: In some language, “EXAM” is coded as “FYBN”. In the same language, how will we code “RESULT”?
A) SFTVMU B) SFTTMU C) QFTVMU D) SFTVNU
Answer: The first step is to detect the code. For that, we need to focus on the word EXAM. The first letter E in code is F, similarly, the code for X is Y, for A it is B and for M it is N. Thus we see that in this language the alphabet is shifted to one step to the front. Thus the code for R will be S and hence the correct option here is
A) SFTVMU
Example 2. In a certain code, ‘MISSIONS’ is written as ‘MSIISNOS’. How is ‘ONLINE’ written in that code?
A) OLNNIE B) ONILEN C) NOILEN D) LNOENI E) ONNLIE
Answer: First and last letter remains the same. The others interchange their positions in pair of two. So, NL becomes LN IN become NI so code of ONLINE will be A) OLNNIE
Type 2:- Coding Of Numbers and Symbols
In this type of coding either numerical code values are assigned to a word or alphabetical code letters are assigned to the numbers. Sometimes, alphanumeric characters or special symbols are also assigned to a word or a number. In this, each alphabet or words are assigned to the numeric values we should observe the given letters and the assigned values and use the same rule for decoding the value to of given code. Some examples are given below:
Example 1: If APPLE is coded as 25563, RUNG is coded as 7148. Then PURPLE is coded as ??
Answer: Putting the numerical values of the words we get an individual number for each character. therefore while decoding the word PURPLE we use individual character numbers and hence we conclude that
PURPLE – 517563
Example 2 : If GOODNESS is coded as HNPCODTR, then how GREATNESS can be written in that code?
(a) HQZSMFRT (b) HQFZUFRTM (c) HQFZUODTR (d) HQFZUMFRT
Solution: (d)HQFZUMFRT Clearly, the letters in the word GOODNESS are moved one step forward and one step backward, alternately to obtain the letters of the code.
Example 3 : If CUP = 40, then KITE = ?
(a) 10 (b) 20 (c) 30 (d) 45
Solution: (d) 45 Using forward letter positions,
