(IGP) IAS Pre Paper - 2: GS - General Mental Ability - Coding-Decoding

What is Coding-Decoding ?

For transmitting secret messages from one place to another, especially in defense services, Coding is used. Decoding is the ability to break the secret code. The codes are based on various principles or patterns. In CSAT, questions based on coding-decoding could be given to judge the intelligence and mental ability of the candidates. The coded word itself does not make any sense unless we know the coding principle. For coding-decoding, following basic knowledge is required.

1. Forward Order of Letters

2. Reverse Order of Letters

3. Opposite Letters

A-Z, H-S, B-Y, I-R, C-X, J-Q, D-W, K-P, E-V, L-0, F-U, M-N, G-T.
The questions based on coding-decoding are broadly categorised into following categories

Type 1

Coding with Alphabet Letters: In such questions, the letters do not stand for themselves but are allotted some other values based on some logical patterns or analogies. By deciphering the principles or pattern involved the candidates are required to decode the coded word.

Example l: As ‘COUNSEL’ is to BITIRAK’ So ‘GUIDANCE’ is to
(a) FOHYZJBB
(b) HOHYBJBA
(c) FPHZZKAB
(d) FORHYZJBB

Solution. (a) The pattern is

C – 1 = B
O – 6 = I
U – 1 = T
N – 5 = I
S – 1 = R
E – 4 = A
L – 1 = K

Example 2: In a certain code, TERMINAL is written as SDQLJOBM. How is CREDIBLI written in that code?
(a) BQDCJCMF
(b) BQDCHAKD
(c) DSFEJCMF
(d) DSFEHAKD
Solution. (a)

On the basis of this rule CREDIBLE will be written as BQDCJCMF.

Type 2

Coding with Numbers: The principle of coding with numbers is similar to that of coding with letters except the use of digits.

Example 3: If in a certain language, E is coded as 2, H is coded as 1, N is coded as 7, P is codec as 5, A is coded as 0, T is coded as 8 and L is coded as 3, how is ELEPHANT coded in that language ?
(a) 23251078
(b) 32210587
(c) 23527801
(d) 22315078
Solution. (a) E = 2, L = 3, E = 2, P = 5, H = 1, A = 0, N = 7, T = 8 Hence, only (a) is valid.

Example 4: In a certain language, 1 is coded as C, 6 is coded as E, 0 is coded as L, 2 is coded a; G and 3 is coded as O. How is 1300626 coded in that language ?
(a) OLCGELE
(b) EGEOLEL
(c) COLLGEE
(d) COLLEGE
Solution. (d)         1 = C, 3 = 0,                         0 = L
                             0 = L, 6 = E,                         2 = G,                 6 = E

Hence, only (d) is valid.

Type 3

Mixed coding (Alphabets + Digits): In such questions, both letters and numbers are assigned as code The candidates are required to identify the analogy given in the questions.

Example 5: If ‘INDIA’ stands for ‘I - 14 - D - 9 - A’ and NEPAL’ stands for N - 5 _ P _ 1 _ L, then how will you code the GIRL ?
(a) G9R12
(b) G15R10
(c) G10R9
(d) G9R11
Solution. (a) Assign the alphabetical number to the letters.

Type 4

Miscellaneous types: In such questions, a careful deciphering is required to find out the patterns.

Example 7: If FRANCE’ is coded as NCEFRA’ and ‘CANADA’ is coded as ADACAN, then how will you code ‘MEDICINE’?
(a) CNIEMEDI
(b) CINEDEMI
(c) CINEMEDI
(d) CINEDEIM
Solution.(c) The first half part is transferred after the second half part. The coding is made as follows

So, the code of MEDICINE will be coded as ‘CINEMEDI’.
Some More Solved Examples

Example 8: If A = Z, B = Y, C = X and so on, then what will be the code of BLACK?
(a) OYZXP
(b) YOZXP
(c) YOZPX
(d) YOXZP
Solution. (b) Now, the code of BLACK is YOZXP.

Example 9: If FOOD is coded as ENNC, then decode the code of SPEED.
(a) RODDC
(b) RDOCC
(c) RODCD
(d) ROCDC
Solution. (a) Here, each letters is allotted the value of its preceding letter in the sequence. So the code of SPEED is RODDC.

Example 10: If INLAND is coded as DNALNI, how will POSTED be coded?
(a) DESTOP
(b) DETOPS
(c) DETSPO
(d) DETSOP
Solution. (a) Now, reverse the letters of the word. So, the code of POSTED will be DETSOP.

Example 11: If EXPORT is coded as USPQYF, then how will CAPITAL be coded?
(a) MBJUQBD
(b) MBUJQBD
(c) BMUJQBD
(d) MBUJQDB
Solution. (b) Reverse the word and use next alphabet as code. So, the answer is MBUJQBD.

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