Coding Decoding
About This Cheat Sheet
Your complete guide to Coding Decoding for competitive exams. This cheat sheet helps you identify patterns, apply rules, and decode messages quickly using logical reasoning.
📝 Types of Coding
- Letter Coding
- Number Coding
- Symbol Coding
- Mixed Coding
- Word to Code
- Code to Word
🔤 Letter Coding Techniques
- Forward/Backward Positions
- Reverse Alphabet (A↔Z)
- Skip Patterns
- Alphabetical Positions (A=1, B=2...)
- Reverse Positions (A=26, B=25...)
- Letter Shifting (Caesar Cipher)
🔢 Number Coding Techniques
- Number Positions
- Operations on Numbers
- Sum of Digits
- Reverse Order
- Square/Cube of Numbers
- Product of Positions
🔣 Symbol & Mixed Coding
- Symbols Representing Letters
- Symbols Representing Numbers
- Symbols Representing Operations
- Letters + Numbers + Symbols
- Letter-to-Letter Mapping
- Number-to-Letter Mapping
🎯 Problem Types
- Finding the Code Rule
- Applying Rule to New Word
- Decoding Code to Original Word
- Coding by Analogy
- Pattern Recognition
- Mixed Operations
📚 Exam Categories
- SSC & Banking
- Railways & UPSC
- CAT & MBA Entrance
- Defence & Insurance
- Placement Tests
- Other Competitive Exams
🔤 Letter Values
A=1, B=2 ... Z=26
Positional Values🔄 Reverse Alphabet
A↔Z, B↔Y, C↔X
Reverse Positions📏 Fixed Shift
A→C, B→D, C→E
Caesar Cipher➕ Alternating
+1, -2, +3, -4
Variable Pattern🔤 Letter Coding Examples
📏 Fixed Shift
- Question: CAT → D B U
- Pattern: +1, -1, +1
- Rule: C→D (+1)
- A→B (+1), T→U (+1)
- Answer: CAT → DBU
- +1 Shift
🔄 Reverse Alphabet
- Question: DOG → WLT
- Pattern: A↔Z
- Rule: D→W (Reverse)
- O→L (Reverse), G→T (Reverse)
- Answer: DOG → WLT
- Reverse Positions
➕ Alternating Shift
- Question: APPLE → BQQLD
- Pattern: +1, +1, -1, -1
- Rule: A→B (+1)
- P→Q (+1), P→Q (+1)
- Answer: APPLE → BQQMD
- Alternating
🔢 Number Coding Examples
🔢 Operations on Numbers
🎯 Quick Problem Examples
📝 Find the Code
- Given: CAT = 3120
- Find: DOG
- C=3, A=1, T=20
- D=4, O=15, G=7
- Answer: 4157
📝 Decode the Code
- Given: 15 14 5 = ONE
- Find: 20 23 15
- 15=O, 14=N, 5=E
- 20=T, 23=W, 15=O
- Answer: TWO
📝 Symbol Coding
- Given: ∆ = A, ✪ = B, ◊ = C
- Find: ✪ ◊ ∆
- ∆ = A, ✪ = B, ◊ = C
- ✪ ◊ ∆ = B C A
- Answer: BCA
📋 Quick Reference: Coding Patterns
🔤 Letter Values
- A=1, B=2 ... Z=26
- A=26, B=25 ... Z=1
- Vowels: A=0, E=1, I=2...
- Consonants: B=1, C=2...
- Sum of letters = value
🔄 Common Shifts
- +1 Shift: A→B, B→C
- -1 Shift: A→Z, B→A
- +3 Shift: A→D, B→E
- Reverse: A→Z, B→Y
- Alternating: +1, -2, +3
🔢 Number Operations
- Sum of digits
- Product of digits
- Square of number
- Cube of number
- Reverse number
- Add/Subtract fixed number
🎯 How to Solve Coding Decoding Questions Quickly
The Golden Rule: The key to solving coding decoding questions is to identify the pattern in the given code. Look for relationships between the original word/phrase and the coded form – the pattern will usually be consistent.
Step-by-Step Approach:
- Step 1: Compare the original with the coded word
- Step 2: Look for patterns – shifting, reversing, positional values
- Step 3: Identify the rule used (forward/backward, addition/subtraction)
- Step 4: Apply the same rule to the target word
- Step 5: Verify your answer by checking consistency
Common Mistakes to Avoid:
- ❌ Identifying a pattern that works for one letter but not for others
- ❌ Forgetting that letters have positional values (A=1, B=2...)
- ❌ Confusing forward shift with backward shift
- ❌ Overlooking reverse alphabet patterns
Proven Strategy: The "Difference Method" – find the difference between each letter's position in the original word and its position in the coded word. If the difference is constant, it's a fixed shift. If the differences follow a pattern, apply that pattern.
Memory Trick: Remember these common coding patterns:
- 📏 Fixed Shift: Each letter moves by same number (A→C, B→D, C→E)
- 🔄 Reverse Alphabet: A↔Z, B↔Y, C↔X
- 🔢 Positional: A=1, B=2, C=3
- ➕ Alternating: +1, -2, +3, -4 pattern
- 📐 Variable: Each letter follows different rule
💡 Pro Tips for Coding Decoding
✅ Find the Rule First
Always identify the coding rule before attempting to apply it
✅ Use Positional Values
Convert letters to numbers (A=1) – it makes pattern recognition easier
✅ Check All Possibilities
The pattern could be forward, backward, reverse, or alternating
✅ Practice with Variety
Practice different types – letter, number, symbol, and mixed coding
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