 # (Online Course) CSAT Paper – II : 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

 A B C D E F G H I 1 2 3 4 5 6 7 8 9 J K L M N 0 P Q R 10 11 12 13 14 15 16 17 18 S T U V W X Y Z 19 20 21 22 23 24 25 26

## 2. Reverse Order of Letters

 A B C D E F G H I 26 25 24 23 22 21 20 19 18 J K L M N 0 P Q R 17 16 15 14 13 12 11 10 9 S T U V W X Y Z 8 7 6 5 4 3 2 1

## 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