Introduction
Coding-Decoding hides a rule that converts a word or number into a coded form. Your job is to find that rule
from the given example(s) and apply it to a new word/number.
Common Coding Types
| Type | How It Works |
|---|
| Letter shifting | Each letter is shifted forward/backward by a fixed number of positions in the alphabet |
| Substitution coding | A direct letter-word or number-word key is given and applied to a new sentence |
| Number coding | Letters are converted into their alphabet position numbers (A=1...Z=26), sometimes with an added operation |
| Symbol coding | Letters or numbers are represented using unrelated symbols following a hidden pattern |
Q. If CAT is coded as DBU, how is DOG coded in the same language?
Each letter shifts forward by 1: C→D, A→B, T→U. Apply the same shift: D→E, O→P, G→H.
So DOG is coded as EPH.
Q. In a certain code, "sun is bright" is written as "pa ka la", "moon is bright" is written as "la ka ta", and "sun is high" is written as "pa da ka". What does "moon" mean?
"sun is bright" = pa ka la. "moon is bright" = la ka ta. Common words "is bright" → common codes "ka la"... but
"bright" appears with "la" in both, and "is" with "ka" (common to all three). Since "sun" and "high" appear
together with "pa" and "da" (from statement 3), and "sun" also appears in statement 1 with "pa", "sun" = pa.
That leaves "moon" = the code unique to statement 2 that isn't "ka" (is) or shared — moon = ta.
⚠️ Key Insight: In word-code matching questions, always find the word that repeats across two
given statements first — its matching code (the one common to both) is your most reliable anchor point.
💡 Exam Tip: For letter-shift coding, write out the alphabet with position numbers 1-26 as a
quick reference strip — it turns "shift by 3" into simple addition/subtraction instead of manual counting.
✅ Practice Focus: Letter-shift pattern coding · Number-to-letter position coding · Word-code
matching from multiple statements · Symbol-based coding schemes.