Coding

Coding

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Coding-Decoding questions test your ability to decipher a pattern or rule used to encode a word or number. In SSC CGL Tier 1, 2-3 questions appear from this topic. The key is to identify the pattern applied to transform the original word into its coded form.

Common Coding Types:

Type	Example	Pattern
Letter-by-letter shift	A→D, B→E	Each letter shifted by constant
Position-based coding	A→1, B→2	Use alphabetical positions
Opposite letter	A→Z, B→Y	Mirror/reverse alphabet
Word substitution	”Red” = “Blue”	Complete word replacement
Number coding	A=2, B=4	Mathematical operation on positions

Basic Shift Patterns:

• In forward shift (e.g., +1): A→B, Z→A (wrap around)
• In backward shift (e.g., -1): A→Z, B→A
• Shift of n: Each letter moves n positions forward/backward

⚡ SSC CGL Exam Tips:

• Always check if the code is forward or backward shift
• Watch for Z wrapping to A (or vice versa)
• Some codes apply different rules for vowels and consonants
• Number codes may involve adding, subtracting, or multiplying positions
• Look for patterns in first, last, and middle letters separately

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Detailed Coding Patterns with Examples

Type 1: Direct Letter Shift “SECURITY” is coded as “TFDJUSJUZ”. Find the code for “EXAMINE”.

Solution: Compare each letter: S→T (+1), E→F (+1), C→D (+1), U→V (+1), R→S (+1), I→J (+1), T→U (+1), Y→Z (+1). The pattern is a +1 shift for all letters.

Apply the same +1 shift to “EXAMINE”: E→F, X→Y, A→B, M→N, I→J, N→O, E→F Code: FYBNJOF

Type 2: Reverse Alphabet (Opposite) “BOOK” is coded as “YLLP”. Find the code for “PAGE”.

Solution: In a reverse-alphabet code, each letter maps to its mirror: A↔Z, B↔Y, C↔X, and so on. The rule is position + opposite = 27, where A=1 and Z=26.

Check with “BOOK”: B(2)→Y(25), O(15)→L(12), O(15)→L(12), K(11)→P(16). Each pair sums to 27, confirming the rule.

Apply to “PAGE”: P(16) → 27-16 = 11 = K A(1) → 27-1 = 26 = Z G(7) → 27-7 = 20 = T E(5) → 27-5 = 22 = V Code: KZTV

Type 3: Sum of Letter Positions If “TRAIN” is coded as a number, the most common rule is the sum of the alphabetical positions of its letters.

T=20, R=18, A=1, I=9, N=14 Sum = 20 + 18 + 1 + 9 + 14 = 62

Apply the same rule to “BUS”: B=2, U=21, S=19 Sum = 2 + 21 + 19 = 42

When a number code does not match a plain sum, test these standard variations in order: sum of positions, product of positions, sum of squares, or (first position × last position). One of these almost always fits an SSC CGL number-coding question.

General method for number codes:

• Always look for the relationship between consecutive letters
• Check sums, differences, and products of positions
• Confirm the rule on the given example before applying it to the asked word

⚠️ Common Mistakes:

1. Forgetting Z wraps to A
2. Mixing up forward and backward shifts
3. Not checking all letters for multiple patterns
4. Overlooking that vowels and consonants may have different rules

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage with complex patterns and previous year SSC CGL patterns.

Complex Coding Patterns:

Type 1: Alternating Shift Pattern Letters at alternate positions are shifted by different amounts (e.g., +2 then -2).

Word: CODE, pattern +2, -2, +2, -2 C(+2)→E, O(-2)→M, D(+2)→F, E(-2)→C Code: EMFC

Type 2: Vowel-Consonant Differentiation When vowels and consonants are coded differently — for example, vowels shifted by +2 and consonants by -1:

“MEAL”: M(-1)→L, E(+2)→G, A(+2)→C, L(-1)→K Code: LGCK

Type 3: Position-Based Multiplication Each letter’s position is multiplied by a fixed number, and the result becomes the code (or is processed further): A=1×3=3, B=2×3=6, C=3×3=9, and so on.

Type 4: Word Coding (Substitution) Words are replaced by category labels — for example, “Gold” is called “Yellow,” “Silver” is called “Grey.” You must deduce the code words from the relationships given.

Example: If “PARROT” is called “BIRD,” “EAGLE” is called “BIRD,” and “SNAKE” is called “REPTILE,” what is COBRA called? PARROT and EAGLE are both birds, so they map to BIRD. SNAKE is a reptile, so it maps to REPTILE. A cobra is also a reptile, therefore: COBRA = REPTILE ✓

Type 5: Number to Letter Coding Numbers represent the alphabetical positions of letters. Convert each number to its letter: Code: 18-5-3-15-14 18→R, 5→E, 3→C, 15→O, 14→N = RECON ✓

Previous Year SSC CGL Patterns:

SSC CGL 2022: In a certain code, “COMPUTER” is written as “RFUVQNPC”. How will “MEDICINE” be written?

Solution: The reliable way to crack this code is to reverse the original word first, then compare it with the code.

COMPUTER reversed = R-E-T-U-P-M-O-C Code = R-F-U-V-Q-N-P-C

Align them position by position: R→R (first letter unchanged) E→F (+1) T→U (+1) U→V (+1) P→Q (+1) M→N (+1) O→P (+1) C→C (last letter unchanged)

The rule is: reverse the word, keep the first and last letters of the reversed word the same, and shift every middle letter by +1.

Apply this to “MEDICINE”: Reverse MEDICINE = E-N-I-C-I-D-E-M Keep first (E) and last (M) unchanged; shift the middle letters by +1: E → E (unchanged) N → O (+1) I → J (+1) C → D (+1) I → J (+1) D → E (+1) E → F (+1) M → M (unchanged) Result: EOJDJEFM

Exam strategy for hard coding questions:

• If a pattern is not obvious, try reversing the word before comparing
• Check whether the first and last letters are treated separately from the middle
• Eliminate options where code letters are not consistently before or after the originals
• The most common operations are a fixed +n / -n shift, the reverse alphabet, and word reversal

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