It is an important part of the Logical reasoning section in all aptitude related examinations.

• Coding is a process used to encrypt a word, a number in a particular code or pattern based on some set of rules.
• Decoding is a process to decrypt the pattern into its original form from the given codes.

Positions of letter are majorly used to find the logical pattern, which are in the following table.

TYPE 1: Coding with Alphabets

In such questions, the “ALPHABETS” of a word are substituted by some other “DOSKDEHWV”.

You have to find logical patterns to the coding and thereby decode the question.

Practice Questions

1. If in a certain language, MADRAS is coded as NBESBT, how is BOMBAY coded in that code?
a. CPNCBX
b. CPNCBZ
c. CPOCBZ
d. CQOCBZ

2. In a certain code, TRIPPLE is written as SQHOOKD. How is DISPOSE written in that code?
a. CHRONRD
b. CHRONRD
c. ESJTPTF
d. ESOPSID

3. If in a code language. COULD is written as BNTKC and MARGIN is written as LZQFHM, how will MOULDING be written in that code?
a. CHMFINTK
b. LNKTCHMF
c. LNTKCHMF
d. NITKHCMF

4. In a certain code, MONKEY is written as XDJMNL. How is TIGER written in that code?
a. QDFHS
b. SDFHS
c. SHFDQ
d. UJHFS
e. None of these

5. If FRAGRANCE is written as SBHSBODFG, how can IMPOSING be written?
a. NQPTJHOJ
b. NQPTJOHI
c. NQTPJOHJ
d. NQPTJOHJ

6. According to a military code SYSTEM is SYSMET and NEARER is AENRER. What is the code for FRACTION? (UPSC 2016)
a. CARFTINO
b. FRACNOIT
c. CARFTION
d. CARFNOIT

7. If LSJXVC is the code for MUMBAI, the code for DELHI is (UPSC 2018)
a. CCIDD
b. CDKGH
c. CCJFG
d. CCIEF

8. In a code language ‘MATHEMATICS’ is written as ‘LBSIDNUHDR’. How is ‘CHEMISTRY’ written in that code language? (UPSC 2021)
B. BIDNHTSSX
C. BIDLTHSSX
D. DGFLIRUQZ

9. If TAP is coded as SZO. then how is FREEZE coded?
a. EQDFYG
b. ESDFYF
c. GQFDYF
d. EQDDYD

10. In a certain code, FORGE is written as FPTJI. How is CULPRIT written in that code?
a. CSJNPGR
b. CVMQSTU
c. CVNSVNZ
d. CXOSULW

TYPE 2: Coding with Numbers

In this type of questions, alphabets are replaced with numbers or digits.

Common operations involved in coding with numbers:

1. Addition of numbers for each alphabet
2. Multiplication of numbers for each alphabet
3. Reverse order of number for each alphabet

You need to recognise which one is being used in any given question and solve accordingly.

Practice Questions

1. In a certain code, NEWYORK is written as 111, how is NEWJERSEY written in that code?
a. 104
b. 124
c. 134
d. 114

2. In a certain code, HARYANA is written as 8197151, how is DELHI written in that code?
a. 45389
b. 45289
c. 44389
d. 45489

3. In a certain code BOMB is written as 5745 and BAY is written as 529, how is BOMBAY written in that code?
a. 5854329
b. 5745529
c. 5645529
d. 5545529

4. If ROSE is coded as 6821, CHAIR is coded as 73456 and PREACH is coded as 961473, what will be the code for SEARCH?
a. 276413
b. 214763
c. 214673
d. 246173

5. In a certain coding language, if GO = 32 & SHE = 49 then SOME will be equal to?
a. 56
b. 58
c. 62
d. 64

6. If RAMON is written as 12345 and DINESH as 675849, then HAMAM will be written as (UPSC CSAT 2018)
a. 92233
b. 92323
c. 93322
d. 93232

7. If PALAM could be given the code number 43, what code number can be given to SANTACRUZ?
a. 75
b. 85
c. 120
d. 123

8. If MASTER is coded as 4li259, then POWDER will be coded as
a. 765439
b. 765439
c. 765459
d. 765549

9. In a certain code, 15789 is written aa XTZAL and 2346 is written as NPSU. How is 23549 written in that code ?
a. NPTUL
b. PNTSL
c. NPTSL
d. NBTSL

10. If REASON is coded as 5 and BELIEVED as 7, what is the code number for GOVERNMENT?
a. 6
b. 8
c. 9
d. 10

TYPE 3: Direct Coding

Letters/symbols are assigned as code. These questions are relatively easy as each alphabet is directly coded as a separate symbol.

E.g., If “LOINESS”: “*? #@! \$\$’ “MEN”: “^! @” then, “MISSION”: _______

You simply need to write down the corresponding symbols for each alphabet and solve the question.

TYPE 4: Deciphering the Message

Practice Questions

Messages are given in coded language and code for each word or for particular word is asked.

1. “COL TIP MOT” MEANS “SINGING IS APPRECIABLE”,
“MOT BAJ MIN” MEANS DANCING IS GOOD”,
“TIP NOP BAJ” MEANS “SINGING AND DANCING"
Find the code for each word on the basis of above statements.

2. ‘816321’ MEANS ‘THE BROWN DOG FRIGHTENED THE CAT’
‘64851’ MEANS ‘THE FRIGHTENED CAT RAN AWAY’
‘7621’ MEANS ‘THE CAT WAS BROWN’
‘341’ MEANS ‘THE DOG RAN’
Find the code for each word on the basis of above statements.

Type 5: Coding with Substitution

In these questions, a word is replaced by an alternative (substitute). You must then use the substitute as the original word and solve the question.

Practice Questions

1. If ‘cook’ is called ‘butler’, ‘butler’ is called ‘manager’, ‘manager’ is called ‘teacher’, ‘teacher’ is called ‘clerk’ and ‘clerk’ is called ‘principal’, who will teach in a class?

2. If ‘eye’ is called ‘hand’, ‘hand’ is called ‘mouth’, ‘mouth’ is called ‘ear’, ‘ear’ is called ‘nose’ and ‘nose’ is called ‘tongue’, with which of the following would a person hear?

3. 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?

4. If ‘diamond’ is called ‘gold’, ‘gold’ is called ‘silver’, ‘silver’ is called ‘ruby’ and ‘ruby’ is called ‘emerald’, which is the cheapest jewel?

5. If 'oranges' are called 'apples', 'bananas' are called 'apricots', 'apples' are called 'chillies', 'apricots' are called orange and ‘chillies’ are called 'bananas', then which of the following are green in colour?

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