Coding-Decoding is one of the most commonly asked topics in the reasoning section of competitive exams like SSC, Banking, and Railways. It tests a candidate’s ability to understand patterns, logic, and symbol-based relationships between letters, numbers, or words. In this blog, we have provided all the details about Coding-Decoding reasoning question types, important short notes, formulas, tricks for exams, solved questions from 2024–25 exams. Whether you’re preparing for SSC CGL, IBPS PO, or RRB NTPC, this blog will help you prepare for this topic with full confidence.
What Is Coding Decoding in Reasoning?
Coding-Decoding is a logical reasoning topic where words, numbers, or symbols are coded according to a rule, and you have to decipher the rule to decode or encode information. This topic identifies your analytical skills and ability to understand the hidden patterns or logic in a structured format.
It is commonly featured in competitive exams like SSC, Banking, RRB, and State PSCs, testing your:
- Observation skills
- Pattern recognition
- Logical thinking
- Mental visualization
Why Is Coding Decoding Important in Competitive Exams?
Coding-Decoding questions are straightforward, scoring, and help boost your reasoning marks.
| Exam | No. of Questions | Difficulty |
| SSC CGL / CHSL | 1–2 | Easy |
| IBPS PO / SBI PO | 1–2 | Moderate |
| RRB NTPC / Group D | 1 | Easy |
| State PSC / Police | 1–2 | Moderate |
Coding Decoding Reasoning Short Notes
Some of the terms used in coding decoding reasoning questions are as follows:
| Term | Details |
| Letter Coding | Words are coded by replacing each letter with another |
| Number Coding | Numbers are replaced using arithmetic/logical rules |
| Symbol Coding | Symbols replace letters or numbers |
| Substitution Coding | One word substituted by another |
| Deciphering Code | Identifying the logic used for encoding |
| Opposite Letter Concept | A-Z, B-Y, C-X pattern in coding |
Coding Decoding Reasoning Concepts
Some of the concepts used in coding decoding reasoning questions are as follows:
| Concept | Explanation |
| Letter Position | A=1, B=2, …, Z=26; used for alphabet shifts |
| Forward/Backward Coding | Shifting letters by positions (e.g., +2, -3) |
| Reverse Alphabet Mapping | A↔Z, B↔Y, C↔X pattern |
| Pair Letter Coding | Encoding based on letter pairs (e.g., AB → CD) |
| Rule-Based Coding | Code created using consistent rules |
| Mixed Coding-Decoding | Codes given in group of statements to decode |
What Are the Types of Coding Decoding Questions in Reasoning?
You will come across different types of coding-decoding questions in exams.
- Direct Coding – One-to-one mapping of words to codes
- Puzzle-based Coding – Codes hidden in logical puzzles
- Coded Equations / Symbol Coding – Uses symbols to represent words or relations
- Mixed Coding – Multiple sentences with common code fragments to analyze
Coding Decoding Formulas for Reasoning
Though there are no fixed formulas to solve this type of question, some tricks that mostly work while solving Coding Decoding questions are as follows:
- Alphabet Position Formula: A=1 to Z=26
- Reverse Alphabet Formula: Z=1 to A=26
- Letter Shift Rule: A shifted by +2 becomes C (A → C)
- Number Conversion Rules: Sum or difference of alphabet positions used as code
- Symbol Logic: Each symbol stands for a specific word or condition
Coding Decoding Tricks for SSC CGL and Other Exams
Speed is key in reasoning. Tricks that will help you to solve the topic are as follows:
- Note A–Z and Z–A positions beforehand
- Break the code into letter-by-letter mapping
- Check for common prefixes/suffixes in letter coding
- Use elimination when multiple statements are given
- Practice 3–4 variants per type to recognize patterns faster
- Watch out for repeated letters or numbers to spot the rule
- Use number series tricks for numeric coding problems
Solved Coding Decoding Questions from 2024–25 Exams
Some of the recent memory-based questions and their solutions:
SSC CGL 2024 Tier 1 Shift 2 – Memory-Based
Q: If in a certain code, KNIFE is written as MPKHG, how is SWORD coded?
Ans: UXQTF
Explanation: Each letter is shifted by +2 alphabetically. S(+2)=U, W(+2)=Y (wrap around), O(+2)=Q, etc.
IBPS PO Prelims 2024
Q: If ‘MANGO’ is coded as 13111417, how is ‘PEACH’ coded?
Ans: 16153183
Explanation: Use A=1, B=2,…Z=26; convert each letter.
Based on Mock Test
Q: In a certain code language, ‘COLD’ is written as ‘DPME’. How will ‘WARM’ be written?
Ans: XBSN
Explanation: Each letter shifted +1 in the alphabet.
Coding Decoding Concepts for Bank Exams
Bank exams often ask questions from advanced logic-based and symbol-based variations. For example:
Example from IBPS Clerk Mains 2024:
Statements:
‘% means A is the father of B’
‘@ means A is the mother of B’
‘$ means A is the sister of B’
Question: What does the expression “P % Q $ R” mean?
Solution: Translate using given symbols.
- P is father of Q
- Q is sister of R
Common Mistakes to Avoid while Solving Coding Decoding
While solving coding-decoding reasoning questions, candidates must keep the below points in mind:
- Ignoring Alphabet Position Table – Always keep A–Z values handy.
- Overcomplicating Simple Logic – Try simple shifts before complex patterns.
- Forgetting Reverse Alphabet Logic – Sometimes coding is done from Z-A.
- Missing Repetitive Patterns – Look for symmetry or repeated logic.
- Poor Time Management – Don’t spend more than 1.5 minutes per question.
FAQs
It involves finding the pattern or logic used to convert one word/number into another.
A=1, B=2, …, Z=26 helps in identifying letter shifts and conversions.
Each letter is moved forward or backward by a fixed number (e.g., A→C is +2).
Words are converted into numbers using alphabet positions or arithmetic logic.
Yes, with elimination and comparison, partial codes can help crack the logic.
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Hi, I’m Tripti, a senior content writer at Oliveboard, where I manage blog content along with community engagement across platforms like Telegram and WhatsApp. With 3+ years of experience in content and SEO optimization related to banking exams, I have led content for popular exams like SSC, banking, railways, and state exams.