Coding-Decoding - The Complete Basics
Learn how letter-shift, position, reverse, and word-substitution codes work in SSC-CGL Coding-Decoding, with a step-by-step method, the EJOTY trick, fully worked examples, and a practice quiz.
By the PadhoDost Team · 📖 6 min read · Updated 4 August 2026
Part of SSC CGL & Banking prep🧠 Think of a secret WhatsApp code
Remember passing secret notes in school where 'A' meant 'B', or you wrote words backwards so the teacher could not read them? Coding-Decoding is exactly that game. Someone hides a real word behind a rule, and your only job is to catch the rule. Once you know the trick used to lock the message, you can lock or unlock any new word instantly.
What Coding-Decoding Really Is
In these questions you are shown a word and its 'code' (a disguised version). The code is made by applying one fixed rule to every letter - shifting letters, replacing them with their alphabet numbers, reversing the order, or swapping whole words. You must discover that rule from the example given, then apply the very same rule to a new word. You are never asked to memorise the code; you are asked to spot the pattern.
The Main Types of Coding
| Type | How it works | Quick example |
|---|---|---|
| Letter shift | Move each letter forward/back by a fixed number | CAT -> DBU (each +1) |
| Reverse / opposite | Replace each letter by its mirror (A<->Z) | ACE -> ZXV |
| Number / position | Replace each letter by its alphabet position | CAB -> 3-1-2 |
| Word substitution | Whole words are swapped for code words | 'sun is hot' -> 'pa la ki' |
| Symbol coding | Letters are mapped to signs/symbols | A -> @, B -> # |
How to crack any coding question
- 1Write the code word directly under the original word, letter below letter.
- 2Compare each pair: is there a fixed forward/backward jump? Are they position numbers? Is the order reversed?
- 3Confirm the rule works for EVERY letter, not just the first one or two.
- 4Apply that exact same rule to the target word to build (or break) its code.
- 5Match your answer with the options and eliminate the close traps.
📝 Worked Example - Letter Shift
Q: If DELHI is coded as EFMIJ, how is MUMBAI coded?
Line them up: D->E, E->F, L->M, H->I, I->J. Every letter moves forward by 1.
Rule found: shift each letter +1.
Apply to MUMBAI: M->N, U->V, M->N, B->C, A->B, I->J.
Answer: NVNCBJ.
📝 Worked Example - Word Substitution
'pen is blue' = 'ka na sa' and 'blue is good' = 'sa na ta'. Find the code for 'good'.
The words 'is' and 'blue' appear in both sentences; the common codes are 'na' and 'sa'.
So 'is'/'blue' use na/sa - which means in sentence 1 the leftover word 'pen' = 'ka'.
In sentence 2 the only leftover word is 'good', and the only leftover code is 'ta'.
Answer: 'good' = ta.
Remember these
- ✓Memorise A=1 to Z=26; the EJOTY milestones (5-10-15-20-25) let you find any position fast.
- ✓Opposite letters always add up to 27 (opposite = 27 minus position).
- ✓Place the code under the word and hunt for ONE consistent rule.
- ✓For word-code puzzles, match the common word with the common code.
- ✓The rule must fit every single letter - verify, then apply.
⚡ Quick check
If CAT is written as 3-1-20, how is DOG written in the same code?
Ready to test yourself? 🎯
Lock it in with the practice test for this chapter.
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