CODING AND DECODING

WHAT IS CODING–DECODING

Meaning
• Coding is a process of converting a word, letter, or number into another form using a specific rule
• Decoding is the process of identifying that rule and finding the original or required form

Objective in CSAT
• Identify the hidden rule
• Apply it consistently
• Avoid overthinking

TYPES OF CODING–DECODING IN CSAT

LETTER SHIFT CODING (ALPHABET POSITION)

Concept
• Each letter has a fixed position in the English alphabet
• A = 1, B = 2, …, Z = 26

Pattern
• Letters are shifted forward or backward by a fixed number

Example Logic
• If A is coded as D, then shift = +3
• CAT → F D W (each letter +3)

REVERSE ALPHABET CODING

Concept
• Alphabet is written in reverse order
• A ↔ Z, B ↔ Y, C ↔ X

Example
• CAT → XZG

Used in
• Direct letter substitution questions

WORD CODING

Concept
• Entire word is coded into another word

Patterns Used
• Letter shifting
• Reversal of letters
• Combination of both

Example Logic
• INDIA → AIDNI (reversal)

NUMBER CODING

Concept
• Letters are replaced by numbers based on position
• Or numbers follow arithmetic patterns

Example
• DOG → 4-15-7

SYMBOL CODING

Concept
• Letters or words replaced by symbols

Example
• If A = @, B = #, C = $, then ABC → @#$

MIXED CODING–DECODING

Concept
• Combination of letters, numbers, and symbols
• Rule must satisfy all given conditions

CSAT Tip
• Verify rule with all given examples before answering

STEP-BY-STEP APPROACH TO SOLVE CODING–DECODING

Step 1
• Read the question carefully

Step 2
• Observe input and output

Step 3
• Check letter position or reversal

Step 4
• Apply rule to all parts

Step 5
• Eliminate wrong options

PRACTICE QUESTIONS 

Question 1
If CAT is coded as DBU, how is DOG coded in the same code?

Question 2
If in a certain code, INDIA is written as AIDNI, how will CHINA be written?

Question 3
If A = Z, B = Y, C = X and so on, how will the word BAT be coded?

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Subject: CSAT

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