Coding-Decoding - Complete Guide with Shortcut Methods

What is Coding-Decoding?

Coding-Decoding is a type of reasoning question where words, numbers, or letters are coded in a specific pattern. The candidate needs to identify the pattern and decode the given information.

Types of Coding-Decoding

Here are the most common types of coding-decoding:

Letter Coding: Letters are coded based on their position in the alphabet or a specific pattern.
Number Coding: Numbers are assigned to letters or words based on a specific rule.
Symbol Coding: Symbols are used to represent letters or words.
Mixed Coding: A combination of letters, numbers, and symbols is used.
Substitution Coding: One set of letters is substituted with another set.
Deciphering Message Word Codes: Words are coded based on a specific rule or pattern.

Alphabet Positions and Tricks

1. Alphabet Positions: Each letter in the English alphabet has a specific position:

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

2. EJOTY Trick: To remember the positions of E, J, O, T, Y, use the code EJOTY:

E = 5
J = 10
O = 15
T = 20
Y = 25

3. Opposite Letters: Letters opposite to each other in the alphabet have a sum of 27:

A (1) ↔ Z (26): 1 + 26 = 27
B (2) ↔ Y (25): 2 + 25 = 27
C (3) ↔ X (24): 3 + 24 = 27
D (4) ↔ W (23): 4 + 23 = 27
E (5) ↔ V (22): 5 + 22 = 27
F (6) ↔ U (21): 6 + 21 = 27
G (7) ↔ T (20): 7 + 20 = 27
H (8) ↔ S (19): 8 + 19 = 27
I (9) ↔ R (18): 9 + 18 = 27
J (10) ↔ Q (17): 10 + 17 = 27
K (11) ↔ P (16): 11 + 16 = 27
L (12) ↔ O (15): 12 + 15 = 27
M (13) ↔ N (14): 13 + 14 = 27

Examples of Coding-Decoding

1. Letter Coding

Example: If "CAT" is coded as "3120", how is "DOG" coded?

Solution: Each letter is replaced by its position in the alphabet. C=3, A=1, T=20. So, DOG = 4(D) + 15(O) + 7(G) = 4157.

2. Number Coding

Example: If "APPLE" is coded as "12512", how is "ORANGE" coded?

Solution: Each letter is replaced by its position in the alphabet. A=1, P=16, L=12, E=5. So, ORANGE = 15(O) + 18(R) + 1(A) + 14(N) + 7(G) + 5(E) = 151811475.

3. Symbol Coding

Example: If "SUN" is coded as "@#$", how is "MOON" coded?

Solution: Each letter is replaced by a unique symbol. S=@, U=#, N=$. So, MOON = M=%, O=&, N=$. Thus, MOON = %&&$.

4. Mixed Coding

Example: If "TIGER" is coded as "20@9#5", how is "LION" coded?

Solution: Letters are replaced by their positions and symbols. T=20, I=@, G=9, E=#, R=5. So, LION = 12(L) + @(I) + 15(O) + #(N) = 12@15#.

5. Substitution Coding

Example: If "HOT" is coded as "JGQ", how is "COLD" coded?

Solution: Each letter is shifted forward by 1. H→J, O→G, T→Q. So, COLD = E(P) + Q(O) + N(L) + F(D) = EQNF.

6. Deciphering Message Word Codes

Example: If "HELLO" is coded as "KHOOR", how is "WORLD" coded?

Solution: Each letter is shifted forward by 3. H→K, E→H, L→O, O→R. So, WORLD = ZRUOG.

Shortcut Methods for Quick Solving

1. Memorize Alphabet Positions: Memorize the positions of letters in the alphabet (A=1 to Z=26) for quick calculations.

2. Reverse Alphabet Positions: Memorize the reverse positions (A=26 to Z=1) for reverse coding problems.

3. Look for Patterns: Identify patterns like letter shifting, alternating letters, or repeating sequences.

4. Use Keywords: If a keyword is given, use it to encode or decode the message.

5. Practice Common Codes: Practice common coding patterns like Caesar Cipher (shifting letters) and substitution codes.

MCQ Questions

Q1: If "APPLE" is coded as "12512", how is "GRAPE" coded?

Options: A) 718116 B) 71815 C) 71816 D) 71817

Answer: B) 71815 (G=7, R=18, A=1, P=16, E=5).

Q2: If "TIGER" is coded as "20@9#5", how is "BEAR" coded?

Options: A) 2@5#1 B) 2@5#18 C) 2@5#17 D) 2@5#19

Answer: B) 2@5#18 (B=2, E=@, A=5, R=#18).

Q3: If "SUN" is coded as "@#$", how is "MOON" coded?

Options: A) %&&$ B) %&$& C) %$$& D) %&$%

Answer: A) %&&$ (M=%, O=&, N=$).

Conclusion

Coding-Decoding questions can be solved quickly with practice and the right approach. Memorize shortcuts, identify patterns, and practice regularly to improve your speed and accuracy. Good luck!