Coding–Decoding Notes
Coding–Decoding is an important topic in reasoning for competitive exams. It involves converting one form of data into another, following a specific rule or pattern, and then decoding it back. Understanding the logic behind the coding is key to solving these questions quickly.
This is a common section in competitive exams such as SSC, Banking, RRB, Defence, and State PSCs, where speed and accuracy are tested.
Types of Coding–Decoding
- Letter Coding
A word’s letters are replaced by other letters following a fixed rule.
Example: CAT → DBU (Rule: +1 shift to each letter). - Number Coding
Letters are replaced with numbers based on their alphabetical position or a predefined pattern.
Example: CAT → 3 1 20 (A=1, B=2, … Z=26). - Symbol / Conditional Coding
Symbols or given conditions represent certain words or statements.
Example: “#” means “greater than” and “@” means “equal to”. - Substitution Coding
Words are replaced with other fixed words.
Example: “Pen is blue” = “ka mo ta” → Common words reveal the meaning. - Mixed Coding
Combination of more than one type of coding in a single question.
All these types of questions from coding–decoding are already solved on our YouTube channel Wisdom Helps — you can find explanations and previous-year questions there.
Before Solving
Before solving any coding–decoding problem, learn the place values (A=1 ... Z=26). Practice these values until they become instant — it saves time during exams.
Place Value Table
| Letter | Value | Letter | Value | Letter | Value |
|---|---|---|---|---|---|
| A | 1 | J | 10 | S | 19 |
| B | 2 | K | 11 | T | 20 |
| C | 3 | L | 12 | U | 21 |
| D | 4 | M | 13 | V | 22 |
| E | 5 | N | 14 | W | 23 |
| F | 6 | O | 15 | X | 24 |
| G | 7 | P | 16 | Y | 25 |
| H | 8 | Q | 17 | Z | 26 |
| I | 9 | R | 18 |
Reverse Order / Opposite Order
| A | B | C | D | E | F | G | H | J | K | L | M |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Z | Y | X | W | V | U | T | S | Q | P | O | N |
Practice More
Try practicing with PDFs and mock tests to improve speed and accuracy. Download notes and attempt quizzes regularly to strengthen your skills. First learn place values well, then start solving problems — it will become easy.
Shortcut for Place Values
Most effective method: write names or words and note each letter’s place value. Example:
W I S D O M 23 9 19 4 19 13
Usual method: memorise anchors E=5, J=10, O=15, T=20, Y=25 and use them to find nearby letters quickly.
Example: A=1 → F = E(5) + 1 = 6 ; S = T(20) − 1 = 19.
Video Class
Watch the video explanations here: