The CODING-DECODING test is given to judge the candidate's ability to decipher the rule which is applied for coding a particular message and break the code to reveal the message.
Coding and Decoding form a dedicated part of the Reasoning Section in various competitive exams but the level of questions differs in them. In order to have a clear insight into the questions on Coding-Decoding, it is better to discuss each type of question separately.
What is the approach to solving the questions of this section?
- Observe alphabets or numbers given in the code keenly.
- Find the sequence it follows whether it is ascending or descending.
- Detect the rule in which the alphabets/numbers/words follow.
Coding and Decoding are classified into several types:
Type 1: Letter Coding.
Type 2: Number Coding.
Type 3: Substitution.
Type 4: New Type of Coding.
Let us analyse them in detail
Type 1: Letter Coding:
In this type, the real alphabets in a word are replaced by certain other alphabets according to a specific rule to form its code. The candidate is required to detect the common rule and answer the questions accordingly.
Case 1: To form the code for another word
If in a certain language MYSTIFY is coded as NZTUJGZ, how is NEMESIS coded in that language?
Sol. Clearly, each letter in the word MYSTIFY is moved one step forward to obtain the corresponding letter of the code.
M Y S T I F Y
N Z T U J G Z
So, in NEMESIS, N will be coded as O, E as F, M as N and so on. Thus, the code becomes OFNFTJT.
Case 2: To find the word by analyzing the given code (DECODING)
If in a certain language BZQQNL is coded as CARROM, which word will be coded as HOUSE?
Sol: Each letter of the word is one step ahead of the corresponding letter of the code
B Z Q Q N L H O U S E
C A R R O M I P V T F
So, H is coded as I, O as P, U as V, S as T and E as F. HOUSE is coded as IPVTF.
Type 2: NUMBER CODING
In these questions, either numerical code values are assigned to a word or alphabetical code letters are assigned to the numbers. The candidate is required to analyze the code as per the directions.
Case 1: When numerical code values are assigned to words
If in a certain language A is coded as 1, B is coded as 2, and so on, how is BIDDIC is coded in that code?
As given the letters are coded as
A B C D E F G H I
1 2 3 4 5 6 7 8 9
So in BIDDIC, B is coded as 2, I like 9, D as 4 and C as 3. Thus, BIDDIC is coded as 294493
Case 2: Number for letter coding.
In a certain code, 2 is coded as P, 3 as N, 9 as Q, 5 as R, 4 as A and 6 as B. How is 599423 coded in that code?
SOL: Clearly as given 5 is coded as R, 9 as Q, 4 as A, 2 as P, and 3 as N. So, 599423 is coded as RQQAPN
In this section, object names are substituted with different object names. We should carefully trace the substitution and answer the given question.
If white is called blue, blue is called red, red is called yellow, yellow is called green, green is called black, black is called violet and violet is called orange, what would be the colour of human blood?
Sol: The colour of the human blood is ‘red’, and as it is given that ‘red’ is called ‘yellow’. So, the colour of human blood is ‘yellow’.
NEW TYPE OF CODING
This is a kind of coding recently included in the Reasoning section. In this type of question either alphabetical code values are assigned to symbols or symbols are assigned to alphabets. The candidate is required to analyze the code as per direction.
In a certain code ‘TOME’ is written as @ $ * ? and ARE is written as ‘ • £ ? ’ How can ‘REMOTE’ be written in that code?
Sol: From the data we have T = @, O = $, M = *, E = ? and A = •, R = £, E = ?
Hence REMOTE is coded as £ ? * $ @ ?
Some Useful Tricks: -
Trick 1: Use EJOTY to remember the position of the alphabet (Total=26) in series.
Opposite position of letters (A=26, B=25 …… Z=1)
Opposite of each letter (A is opposite to Z and B is opposite to Y and C is opposite to X …… and so on)
Trick 2: The reverse order can be obtained by subtracting the position from 27 say
Example: Opposite of M = 13 is 27-13= 14 = Four-teen = N
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