Coding and Decoding

Easy

Coding-decoding problems encode words or letters using a specific rule, and you must identify the rule to decode or encode new inputs.

Why It Matters

Common in placement and government exam reasoning sections. Tests the ability to identify transformation patterns quickly.

How It Works

Main types: Letter shift coding (each letter shifted by a fixed number, e.g., A→D, B→E), reverse alphabet coding (A=26, B=25... Z=1), position-based coding (letter replaced by its position number), substitution coding (words map to code words — identify which word maps to which code), and mixed operations (reverse + shift). Strategy for word-pair substitution: find two coded words that share a word, and deduce the mapping by elimination.

Example

If COME is coded as DPNF (each letter +1), then HELP is coded as IFMQ.

Common Mistakes

Students often apply a shift pattern found from the first letter to all letters without checking. In word-substitution types, they match word order instead of doing proper elimination.