Coding-Decoding

1. What is Coding-Decoding?

Coding-Decoding is a reasoning ability test where words, numbers, or symbols are encoded using specific patterns or rules, and you need to decode them based on the given logic. It tests your pattern recognition and logical thinking skills.

Pattern Recognition

Logical Thinking

Rule Identification

Application Skills

Simple Definition: Coding-Decoding means converting information into codes and then deciphering those codes based on specific rules.

2. Types of Coding-Decoding

Major Categories of Coding-Decoding

Based on Content

Letter Coding

Alphabet-based patterns

Number Coding

Number-based patterns

Substitution Coding

Word/symbol replacement

Based on Complexity

Mixed Coding

Combination of different types

Matrix Coding

Table-based coding

Conditional Coding

Rule-based coding

3. Letter Coding

Common Letter Coding Patterns

Forward Shift

A→B, B→C, C→D

Backward Shift

B→A, C→B, D→C

Opposite Letter

A→Z, B→Y, C→X

Position Number

A→1, B→2, C→3

Letter Coding Examples

Word	Code	Pattern	Decoded
APPLE	BQQMF	+1 to each letter	A→B, P→Q, P→Q, L→M, E→F
ZEBRA	YDAQZ	-1 to each letter	Z→Y, E→D, B→A, R→Q, A→Z
CODE	XLWV	Opposite letters	C→X, O→L, D→W, E→V
MAN	NBO	+1 to each letter	M→N, A→B, N→O

4. Number Coding

Common Number Coding Patterns

Position Based

A=1, B=2, C=3

Reverse Position

Z=1, Y=2, X=3

Mathematical Operations

+N, -N, ×N, ÷N

Digit Sum

Sum of letter positions

Number Coding Examples

Word	Code	Pattern	Explanation
CAT	3 1 20	Position numbers	C=3, A=1, T=20
DOG	23 12 5	Reverse position	D=23, O=12, G=5
BALL	6	Sum of positions	B(2)+A(1)+L(12)+L(12)=27→2+7=9
MAN	28	Product of positions	M(13)×A(1)×N(14)=182

5. Substitution Coding

Substitution Coding Patterns

1

Word Substitution

Replacing words with codes

2

Symbol Substitution

Using symbols for words/letters

3

Number Substitution

Numbers representing words

4

Mixed Substitution

Combination of different substitutions

Substitution Coding Examples

Code	Meaning	Example	Decoded
apple = red	fruit = color	banana = ?	yellow
@ = A, # = B	symbols for letters	@# = ?	AB
1 = good, 2 = bad	numbers for words	12 = ?	good bad
red = danger	color = meaning	green = ?	go/safety

6. Mixed Coding-Decoding

Mixed Coding Patterns

Combination Types

Letter-Number Mix

Combining letter and number codes

Symbol-Letter Mix

Mixing symbols with letters

Multiple Patterns

Different rules for different parts

Complex Patterns

Condition-based

Rules change based on conditions

Position-based

Different coding for positions

Multi-step

Multiple operations required

Mixed Coding Examples

Type	Example	Pattern	Solution
Letter-Number	A1B2C3	Letter + Position	A=1, B=2, C=3
Symbol-Letter	@A #B $C	Symbol + Letter	@=A, #=B, $=C
Multiple Rules	CAT = 3120, DOG = 4157	Position numbers	C=3, A=1, T=20
Condition-based	Vowel +1, Consonant -1	Different rules	A→B, B→A, C→B

7. How to Solve Coding-Decoding Questions

Step-by-Step Approach:

1

Identify the Pattern Type

Determine if it's letter, number, substitution, or mixed

2

Analyze Given Examples

Study the coding-decoding pairs provided

3

Establish the Rule

Formulate the coding pattern or rule

4

Apply and Verify

Apply rule to solve and verify with examples

Always test your identified pattern with multiple examples to ensure it works consistently!

8. Common Delhi Police / SSC Exam Facts

Letter Coding → Most Common

Number Coding → Frequent

Time Limit → 45-60 seconds per question

Pattern Recognition → Key Skill

Practice → Essential for Speed

Mixed Coding → Higher Difficulty

9. Quick Recap

Coding Type	Key Focus	Common Patterns
Letter Coding	Alphabet Patterns	Forward/Backward shift, Opposite letters
Number Coding	Position Numbers	Alphabet position, Reverse position, Operations
Substitution Coding	Replacement Rules	Word replacement, Symbol codes, Number codes
Mixed Coding	Combination Patterns	Multiple rules, Conditional coding, Multi-step

You've completed Coding-Decoding!

Courage Tip: Remember to always identify the pattern from given examples first, then apply it consistently. Practice different types of coding-decoding to improve your speed in recognizing patterns quickly during exams.