1. What this chapter covers

Coding (known in Hindi as Sanketik Bhasha or Kootlekhan) is the process of converting a message, word, number, or symbol into an encrypted secret representation following a definite, consistent logical rule. In competitive exams (including RPSC, Rajasthan Police, REET, CET, SSC, and Railway recruitments), coding questions evaluate your pattern recognition speed, familiarity with the English alphabet sequence, and mathematical reasoning.

A coding problem presents an original word (plaintext) and its code (ciphertext). Your task is to identify the underlying transformation rule and apply that exact rule to code a new target word.

The principal types of coding covered in this chapter are:

  1. Letter Coding: Shifting letters forward or backward, alternating shifts, opposite letter replacement, and positional transpositions.
  2. Number Coding: Assigning numbers based on alphabetical position ranks, digit sums, opposite ranks, or mathematical operations.
  3. Direct Coding: Mapping each letter to a specific digit or symbol directly from reference words without an arithmetic formula.
  4. Mixed & Pattern Transposition: Reversing words, swapping letter pairs, or rearranging letter positions in geometric or diagonal patterns.

2. Alphabet positional values and the EJOTY rule

Every question in letter and number coding relies on the positional values of the 26 letters of the English alphabet.

Forward positional ranks (Left to Right: A = 1 to Z = 26)

Letter A B C D E F G H I J K L M
Rank 1 2 3 4 5 6 7 8 9 10 11 12 13
Letter N O P Q R S T U V W X Y Z
Rank 14 15 16 17 18 19 20 21 22 23 24 25 26

The EJOTY landmark formula

To recall any letter position within seconds without writing the entire alphabet: - **E** = 5 - **J** = 10 - **O** = 15 - **T** = 20 - **Y** = 25

Example: To find the position of S, observe that S immediately precedes T (20), so S = 19. To find G, observe that G is 2 steps after E (5), so G = 7.

3. Reverse positions and Opposite Letter Pairs

The Rule of 27

For any letter in the English alphabet: $$\text{Forward Position} + \text{Reverse Position} = 27$$ $$\text{Reverse Position} = 27 - \text{Forward Position}$$

For example, for D (Forward Rank = 4): $$\text{Reverse Rank} = 27 - 4 = 23$$

Opposite Letter Pairs (Sum of Ranks = 27)

Two letters are opposite when one occupies the same rank from the left as the other from the right:
Pair Letters Ranks Memory Mnemonic
1 A - Z $1 + 26 = 27$ Azad / A to Z
2 B - Y $2 + 25 = 27$ Boy
3 C - X $3 + 24 = 27$ Crax
4 D - W $4 + 23 = 27$ Dew
5 E - V $5 + 22 = 27$ Evening / Love
6 F - U $6 + 21 = 27$ Ful / Fair Unfair
7 G - T $7 + 20 = 27$ G.T. Road
8 H - S $8 + 19 = 27$ High School
9 I - R $9 + 18 = 27$ Indian Railway
10 J - Q $10 + 17 = 27$ Jungle Queen
11 K - P $11 + 16 = 27$ Kurta Pajama / Kanpur
12 L - O $12 + 15 = 27$ Light On / Love
13 M - N $13 + 14 = 27$ Man

4. Fundamental Letter Coding Patterns

  1. Constant Forward Shift (+k): Each letter moves forward by a fixed number of places.
    • Example: If CAT is coded as DBU (+1 each), then DOG is EPH.
  2. Constant Backward Shift (-k): Each letter moves backward by a fixed number of places.
    • Example: If FISH is coded as EHRG (-1 each), then BIRD is AHQC.
  3. Progressive / Variable Shift (+1, +2, +3...):
    • Example: If PEN is coded as QGP: P(+1)=Q, E(+2)=G, N(+3)=Q.
  4. Alternating Shift (+1, -1, +1, -1...):
    • Example: If TRIP is coded as UQJO: T(+1)=U, R(-1)=Q, I(+1)=J, P(-1)=O.
  5. Opposite Letter Coding:
    • Example: If KING is coded as PRMT (K-P, I-R, N-M, G-T), then ROSE is ILHV.
  6. Cross / Diagonal Transposition:
    • Letters within adjacent pairs or halves swap places: AB CD EF -> BA DC FE.
  7. Reverse Word Order:
    • APPLE -> ELPPA.

5. Number and Direct Coding Principles

  1. Sum of Ranks:
    • BAT = 2 + 1 + 20 = 23.
    • CAT = 3 + 1 + 20 = 24.
  2. Sum of Opposite Ranks:
    • GO: Opposite of G is T(20), opposite of O is L(12). Sum = 20 + 12 = 32.
    • SHE: Opposite of S is H(8), H is S(19), E is V(22). Sum = 8 + 19 + 22 = 49.
  3. Direct Digit Assignment:
    • In direct coding, numbers do not correspond to alphabet ranks. Compare two given words to extract individual character values:
    • If GIVE = 5137 and BAT = 924, then GATE = G(5), A(2), T(4), E(7) = 5247.

6. Step-by-step practice problems

Practice 01

If 'CAT' is coded as 'DBU', what is the code for 'FOX'?

A. GPY B. GQY C. FOY D. FPX

Practice 02

If 'BIRD' is written as 'AHQC', what is the code for 'CROW'?

A. BQNV B. BQNU C. BPNV D. BRNV

Practice 03

If 'ROAD' is coded as 'URDG', what will 'SWAN' be coded as?

A. VZDQ B. VZCQ C. UXDQ D. WZDQ

Practice 04

If 'STAMP' is coded as 'TVBOS', what is the shift pattern applied to the letters?

A. +1, +2, +1, +2, +3 B. +1, +1, +1, +1, +1 C. +2, +2, +2, +2, +2 D. -1, -2, -1, -2, -3

Practice 05

If 'A' = 1 and 'BAT' = 23, what is the numerical value of 'CAT'?

A. 24 B. 25 C. 22 D. 26

Practice 06

If 'E' = 5 and 'HOTEL' = 60, what is the numerical value of 'LAMB'?

A. 28 B. 26 C. 30 D. 32

Practice 07

If 'GO' = 32 and 'SHE' = 49, what is the value of 'SOME'?

A. 56 B. 58 C. 62 D. 64

Practice 08

If 'APPLE' is written as 'ELPPA', what transformation is used?

A. Full reversal of letter order B. Shift of +1 C. Opposite letters D. Alphabetical sorting

Practice 09

If 'KING' is coded as 'PRMT', what is the code for 'ROSE'?

A. ILHV B. ILGV C. IMHV D. IKHV

Practice 10

If 'GIVE' = 5137 and 'BAT' = 924, what is the code for 'GATE'?

A. 5247 B. 5427 C. 5274 D. 5147

Practice 11

If 'DELHI' is coded as 'CCIDD', what is the decreasing shift pattern?

A. -1, -2, -3, -4, -5 B. -1, -1, -1, -1, -1 C. -2, -3, -4, -5, -6 D. -5, -4, -3, -2, -1

Practice 12

If 'TIGER' is coded as 'VKIGT', what is the shift value for each letter?

A. +2 B. +1 C. +3 D. -2

Practice 13

If 'SYSTEM' is written as 'SYSMET', what structural split is applied?

A. Split into two halves of 3 letters, and each half reversed B. Full reversal C. Alternating swap D. Shift +1

Practice 14

If 'Z' = 52 and 'ACT' = 48, what is the multiplier applied to the position sum?

A. 2 B. 3 C. 4 D. 1

Practice 15

If 'BEAT' is coded as 'YVZG', what is the relationship between paired letters?

A. Opposite letters whose sum is 27 B. Letters shifted by +5 C. Vowels unchanged D. Alphabetical reverse

Practice 16

If 'PENCIL' is coded as 'NCLAGJ', how are letters shifted?

A. Each letter shifted backward by -2 B. Backward by -1 C. Forward by +2 D. Forward by +1

Practice 17

If 'HEATER' is coded as 'KBDQHO', what alternating pattern is followed?

A. +3, -3, +3, -3, +3, -3 B. +2, -2, +2, -2, +2, -2 C. +1, -1, +1, -1, +1, -1 D. +3, +3, +3, -3, -3, -3

Practice 18

If 'LEMON' is coded as 'ELMNO', what sorting principle is applied?

A. Rearranging constituent letters in alphabetical ascending order B. Reverse alphabetical order C. Opposite letters D. Alternating shift

Practice 19

If 'ROSE' = 6821 and 'CHAIR' = 73456, what is the code for 'SEARCH'?

A. 214673 B. 214763 C. 241673 D. 214637

Practice 20

If 'MASTER' is coded as 'OCUVGT', what is the code for 'DOCTOR'?

A. FQEVQT B. FQEWQT C. FPEVQT D. EQEVQT

Practice 21

If 'PRINTER' is coded as '11-18-9-14-20-5-18', what is the rank of letter P?

A. 11 (Reverse rank: 27 - 16 = 11) B. 16 (Forward rank) C. 22 D. 8

Practice 22

If 'ACNE' is coded as '3, 7, 29, 11', what linear formula maps position p to the code?

A. 2p + 1 B. 2p - 1 C. 3p + 1 D. p^2

Practice 23

If 'MACHINE' is coded as '19-7-9-14-15-20-11', what constant is added to each rank?

A. +6 B. +5 C. +7 D. +4

Practice 24

If 'LEADER' is coded as '20-13-9-12-13-26', what is the added constant value?

A. +8 B. +6 C. +10 D. +7

Practice 25

If 'A'=2, 'B'=4, 'C'=6, what is the value of 'INDIA'?

A. 74 B. 72 C. 76 D. 78

Practice 26

If 'BEAT' is coded as 'GIDV', what is the sequence of forward shifts?

A. +5, +4, +3, +2 B. +4, +3, +2, +1 C. +2, +3, +4, +5 D. +5, +5, +5, +5

Practice 27

If 'PRISM' is coded as 'OSHTL', what alternating shift is followed?

A. -1, +1, -1, +1, -1 B. +1, -1, +1, -1, +1 C. -2, +2, -2, +2, -2 D. -1, -1, -1, -1, -1

Practice 28

In circular alphabet coding, what letter is obtained by shifting 'Z' forward by +4?

A. D B. C C. E D. B

Practice 29

If 'REASON' is coded as '5' and 'BELIEVED' as '7', what is the coding principle?

A. Word letter count minus 1 B. Number of vowels C. Number of consonants D. First letter rank

Practice 30

If opposite letters are taken and then shifted forward by +1, what is the code for 'A'?

A. A B. Z C. B D. Y

7. Solutions to practice problems

Answer 01

A. GPY. Each letter is shifted forward by +1: F(+1)=G, O(+1)=P, X(+1)=Y. Thus FOX becomes GPY.

Answer 02

A. BQNV. Each letter is shifted backward by -1: C(-1)=B, R(-1)=Q, O(-1)=N, W(-1)=V. Hence BQNV.

Answer 03

A. VZDQ. Every letter shifts forward by +3: S(19)+3=V, W(23)+3=Z, A(1)+3=D, N(14)+3=Q. Output is VZDQ.

Answer 04

A. +1, +2, +1, +2, +3. S(19)+1=T(20), T(20)+2=V(22), A(1)+1=B(2), M(13)+2=O(15), P(16)+3=S(19). Pattern is +1, +2, +1, +2, +3.

Answer 05

A. 24. Direct sum of forward alphabetical ranks: C(3) + A(1) + T(20) = 24.

Answer 06

A. 28. Sum of forward positions: L(12) + A(1) + M(13) + B(2) = 28.

Answer 07

A. 56. Sum of reverse ranks: S(8) + O(12) + M(14) + E(22) = 56.

Answer 08

A. Full reversal of letter order. The letters of the word are written completely in reverse order from right to left.

Answer 09

A. ILHV. Each letter is replaced by its opposite letter: R-I, O-L, S-H, E-V. The code is ILHV.

Answer 10

A. 5247. Direct character substitution: G=5, A=2, T=4, E=7. Hence GATE = 5247.

Answer 11

A. -1, -2, -3, -4, -5. D(-1)=C, E(-2)=C, L(-3)=I, H(-4)=D, I(-5)=D. Decreasing shift is -1, -2, -3, -4, -5.

Answer 12

A. +2. T(20)+2=V(22), I(9)+2=K(11), G(7)+2=I(9), E(5)+2=G(7), R(18)+2=T(20). Shift is +2 throughout.

Answer 13

A. Split into two halves of 3 letters, and each half reversed. SYSTEM is divided into SYS and TEM. Reversing SYS gives SYS; reversing TEM gives MET. Combined: SYSMET.

Answer 14

A. 2. Z = 26 * 2 = 52. ACT = (1 + 3 + 20) * 2 = 48. The multiplier is 2.

Answer 15

A. Opposite letters whose sum is 27. B-Y (2+25=27), E-V (5+22=27), A-Z (1+26=27), T-G (20+7=27). All are opposite pairs.

Answer 16

A. Each letter shifted backward by -2. P(-2)=N, E(-2)=C, N(-2)=L, C(-2)=A, I(-2)=G, L(-2)=J. Constant shift is -2.

Answer 17

A. +3, -3, +3, -3, +3, -3. H(+3)=K, E(-3)=B, A(+3)=D, T(-3)=Q, E(+3)=H, R(-3)=O. Strict alternating +3, -3.

Answer 18

A. Rearranging constituent letters in alphabetical ascending order. The letters in LEMON are sorted alphabetically: E < L < M < N < O = ELMNO.

Answer 19

A. 214673. Direct digit mapping: S=2, E=1, A=4, R=6, C=7, H=3. Assembling SEARCH gives 214673.

Answer 20

A. FQEVQT. Forward shift of +2 to every letter: D(+2)=F, O(+2)=Q, C(+2)=E, T(+2)=V, O(+2)=Q, R(+2)=T.

Answer 21

A. 11 (Reverse rank: 27 - 16 = 11). P is 16th from left; its reverse position from right is 27 - 16 = 11.

Answer 22

A. 2p + 1. A(1)->2(1)+1=3; C(3)->2(3)+1=7; N(14)->2(14)+1=29; E(5)->2(5)+1=11. Formula is 2p + 1.

Answer 23

A. +6. M(13)+6=19, A(1)+6=7, C(3)+6=9, H(8)+6=14, I(9)+6=15, N(14)+6=20, E(5)+6=11. Constant added is 6.

Answer 24

A. +8. L(12)+8=20, E(5)+8=13, A(1)+8=9, D(4)+8=12, E(5)+8=13, R(18)+8=26. The value added is 8.

Answer 25

A. 74. Double each position (2p): I(18) + N(28) + D(8) + I(18) + A(2) = 74.

Answer 26

A. +5, +4, +3, +2. B(2)+5=G(7), E(5)+4=I(9), A(1)+3=D(4), T(20)+2=V(22). Decreasing shifts +5, +4, +3, +2.

Answer 27

A. -1, +1, -1, +1, -1. P(-1)=O, R(+1)=S, I(-1)=H, S(+1)=T, M(-1)=L. Shift is -1, +1, -1, +1, -1.

Answer 28

A. D. After Z(26), the alphabet restarts: Z+1=A, Z+2=B, Z+3=C, Z+4=D.

Answer 29

A. Word letter count minus 1. REASON has 6 letters: 6 - 1 = 5. BELIEVED has 8 letters: 8 - 1 = 7. Rule is Length - 1.

Answer 30

A. A. Opposite of A is Z. Shifting Z forward by +1 wraps around to A. Hence, A.

8. Quick revision pointers

  1. Always write down the forward numbers (1-26) or use the EJOTY benchmark (5, 10, 15, 20, 25).
  2. Check for Opposite Letters (sum = 27) whenever the code letters appear distant or inverted.
  3. If letters remain the same but order changes, inspect Reversal, Pair Swap, or Half-Split Reversals.
  4. In Number Coding, test whether the number is the sum of forward positions, sum of reverse positions, or multiplied by letter count.
  5. In Direct Coding, cross-check letters common to both given example words to confirm unique digit mappings.

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