Introduction
Coding & Decoding gives you a sample word with its coded form and asks you to encode/decode another word. SSC Stenographer asks 2 to 3 such items per paper. Almost all questions use one of four standard codes — letter shift, opposite-letter, position-number, or word-substitution. After this lesson you will identify the code in 5 seconds and solve in 20.
Core Concept
The four standard code families:
1. Letter shift code. Each letter shifts by a fixed number of positions. Example: CAT → DBU shifts each letter +1.
2. Opposite-letter code. Each letter is replaced by its mirror in the alphabet (A↔Z, B↔Y, etc.). Memorise: A=Z, B=Y, C=X, D=W, E=V, F=U, G=T, H=S, I=R, J=Q, K=P, L=O, M=N.
3. Position-number code. Each letter replaced by its alphabet position (A=1, B=2…). Sometimes squared, doubled or summed.
4. Word-substitution code. Whole words swap meaning — "Sky is Tree, Tree is Cloud, Cloud is Mountain". Then "Birds fly in Tree" really means "Birds fly in Sky".
Real-life analogy: it's like a private gang signal — once you know the key, every message decodes the same way.
Formula Sheet
| Code | Rule |
|---|---|
| Shift +n | Each letter moves n places forward |
| Opposite | A↔Z, B↔Y, C↔X… (sum of positions = 27) |
| Position number | A=1, B=2, …, Z=26 |
| Word substitute | Word A means Word B in the coded language |
Solved Examples
Example 1. If CAT = DBU, then DOG = ?
- Each letter shifts +1: D→E, O→P, G→H.
- Answer: EPH.
Example 2. If MOON = NLLM in opposite-code, decode FRUIT.
- Sum-27 rule: F(6)→U(21), R(18)→I(9), U(21)→F(6), I(9)→R(18), T(20)→G(7).
- Answer: UIFRG.
Example 3. Sky=Tree, Tree=Cloud. "Birds live on Cloud" really means?
- Cloud means Tree in coded language.
- Real meaning: "Birds live on Tree".
- Answer: Tree.
Question Patterns
- Letter-shift code — uniform shift, ±n.
- Opposite-letter code — A↔Z mapping.
- Position-number code — letter to digit mapping.
- Word-substitute code — whole words swap.
- Mixed code — first letter +1, second letter +2 etc.
- Number-to-word reverse — given code, decode original.
Mistakes to Avoid
1. Forgetting wrap-around. Z+1 wraps to A.
2. Confusing forward vs reverse direction. Always check sample to confirm.
3. Mixing position with shift. Position is fixed (A=1); shift varies (+n).
4. Failing to reverse word-substitution. "Cloud means Tree" → when you see Cloud, write Tree.
Exam Importance
| Exam | Frequency | Marks | Notes |
|---|---|---|---|
| SSC Stenographer | High | 2–3 | Shift codes common |
| SSC CGL | High | 3–5 | Mixed codes heavy |
| RRB NTPC | High | 2–4 | Word substitution common |
Why Coding-Decoding is always-asked. SSC Stenographer 2026 asks 2–3 coding items per paper. The variants are limited: letter-shift coding (A→B, B→C: shift by 1), reverse coding (A→Z, B→Y), number-substitution coding (A=1, B=2…), word-substitution coding (DOG = MOON = a fixed word), conditional coding (apply different rules to vowels vs consonants), pattern-based coding (read positions diagonally or in pairs). The 3-step method: (1) Identify the type of coding by comparing one given pair (input → output). (2) Apply the same rule mentally to the question word. (3) Verify with a second given pair if available. The biggest trap: SSC inserts a distractor that uses a similar but slightly different rule (shift by 2 instead of 1, or reverse-and-shift). Always re-check by encoding back. Memorise alphabet positions: A=1, E=5, J=10, M=13, N=14, O=15, T=20, Z=26 — these anchors speed up calculations. Practise 10 coding questions daily; cap each question at 30 seconds.
Quick Revision
- Identify code family in 5 seconds.
- Memorise opposite-letter pairs (sum = 27).
- Watch wrap-around (Z+1 = A).
- For word substitution, swap on read.
- Cap time at 25 seconds.
- Solve 10 PYQ codes daily.
- Verify with sample word.
- Practice mixed shifts (+1+2+3…).
- Letter-shift codes: identify shift by comparing position of each letter in plain vs cipher.
- Reverse-letter codes: A→Z, B→Y, C→X — each letter maps to its 27-minus partner.
- Number-substitution codes: assign A=1…Z=26 or A=26…Z=1; check both before computing.
- Mixed codes: shift varies per position (+1, +2, +3, …) — spot via consecutive-difference check.
- Word-substitution codes: read sentence twice — once to map words, once to decode the question.
- Drill 100 PYQ coding-decoding items to lock the 6 standard code families.
- The 6 families: shift-code, reverse-code, position-code, letter-mapping code, mixed-shift code, word-substitution code.
- For shift codes, the most common shifts are +1, +2, +3, +5, −1, −2 — check small numbers first.
- For reverse codes, A↔Z, B↔Y, C↔X — the sum of position numbers is always 27.
- For position codes, check both A=1 and A=26 conventions — SSC tests both.
- For mixed-shift codes, write differences between plain and cipher letters as a sequence; the sequence often follows a simple pattern.
- SSC Stenographer 2026 typically asks 2–3 coding items — high-speed scoring worth 3–4.5 marks at 25 seconds each.