Coding-Decoding: Decoding a set of symbols or codes | CSAT 2025 Tips | www.gscsat.blogspot.com

Coding-Decoding is a concept often used in reasoning and logical puzzles, where you need to decode a set of symbols, numbers, or letters based on a rule or pattern. It involves figuring out how information is encoded and then applying the reverse process to decode it. The key is recognizing the relationship between the symbols and finding the method or pattern used to encode them.

Types of Coding-Decoding:

1. Letter Substitution: In this type of coding, each letter of a word or phrase is replaced by another letter according to a certain rule (like shifting letters by a fixed number in the alphabet).

   Example:

   • Given a rule: Shift each letter by 2 positions forward.
   • Original word: CAT → Decoded: ECV
   • Explanation: C → E, A → C, T → V (each letter is shifted by 2).

2. Number Substitution: In this type, numbers are assigned to letters or words, and you need to decode them by figuring out the pattern.

   Example:

   • Given a pattern: 1 = A, 2 = B, 3 = C, etc.
   • Encoded message: 3 1 20 → Decoded: CAT
   • Explanation: 3 → C, 1 → A, 20 → T.

3. Letter Shifting (Caesar Cipher): One of the most common types of letter substitution coding is the Caesar Cipher, where each letter of a message is shifted by a certain number.

   Example:

   • Given a rule: Shift each letter by 3 positions forward.
   • Original: HELLO → Encoded: KHOOR
   • Explanation: H → K, E → H, L → O, L → O, O → R.

4. Symbolic Code: In some cases, symbols (such as stars, numbers, or shapes) are used to represent words or letters. You need to deduce what each symbol means and then decode the message.

   Example:

   • Given symbols: ★ ➔ A, ♥ ➔ B, ♦ ➔ C
   • Encoded Message: ★ ♥ ♦ ➔ Decoded: ABC.

5. Mathematical or Logical Patterns: Sometimes, numbers are encoded by using mathematical operations. You may need to reverse the operation to decode the message.

   Example:

   • Given the pattern: Add 5 to the number.
   • Encoded: 8 → Decoded: 3
   • Explanation: To decode, subtract 5 from 8.

6. Reverse Coding: In this method, the letters or numbers are written backward or in reverse order.

   Example:

   • Original word: TABLE → Encoded: ELBAT
   • Explanation: The word is written in reverse.

Solving Coding-Decoding Problems:

To solve these problems, you need to:

1. Identify the pattern: Look for how the code is being formed (shift, reverse, substitution, etc.).
2. Apply the reverse pattern: Once you understand the encoding rule, reverse it to decode the message.
3. Test with examples: Use other examples in the problem to ensure that the rule is consistent and works with all symbols/letters.

Example 1: Shift Cipher

• Given: If "DOG" is written as "FQI" in code, what will "CAT" be written as in the same code?
• Solution:
  • "DOG" → "FQI" (Shifted 2 positions forward)
  • C → E, A → C, T → V
  • Decoded Message: "CAT" → "ECV".

Example 2: Reverse Order

• Given: In a certain code, the word "LAPTOP" is written as "POTPAL". How would "COMPUTER" be written in the same code?
• Solution:
  • The rule is reversing the order of the letters.
  • "COMPUTER" → "RETUPMOC"

Key Points:

• Observe the pattern: Identifying whether the encoding involves shifting, reversing, or substituting is crucial.
• Apply the pattern consistently: Once you recognize the rule, you can apply it to decode any given message.

By understanding and practicing various coding-decoding techniques, you can improve your ability to solve these types of puzzles effectively.