Question & Theory on Coding-Decoding

Chapter 2: Coding–Decoding

Introduction

Coding–Decoding tests the candidate’s analytical reasoning and pattern interpretation ability. It involves converting given words or numbers into coded forms using specific rules. This concept appears widely in Aptitude Questions for Competitive Exams, such as SSC, Banking, Railways, and Defence tests. It checks logical consistency and your ability to detect concealed relationships between letters or numbers.

Types of Questions Asked

  1. Letter Coding:
    Each alphabet in a word is replaced according to a specific pattern. For instance, if CAT = DBU, the rule is +1 to each letter.

  2. Number Coding:
    Here, words are represented by numbers based on alphabetical order, like “DOG = 4 15 7.”

  3. Mixed Coding:
    Combination of numbers, letters, or symbols used interchangeably.

  4. Substitution Coding:
    Certain words or symbols are substituted by others. Example: “Pen means Apple, Book means Pen,” etc.

  5. Matrix Coding:
    Letters are placed in a matrix grid, and codes are given based on coordinates.

Preparation Tips

  • Always decode the pattern from the simplest code first.

  • Compare given examples before decoding new ones.

  • Make small notes on common coding patterns (shift +1, −1, reverse).

Why It Matters

Coding–Decoding improves logical deduction and helps develop a systematic thought process that applies across reasoning sections.