Questions
4 questions
Difficulty
Medium
Importance
High yield for SSC and Banking
Overview
Coding-Decoding tests your ability to identify hidden patterns within alphanumeric sequences to translate data into a given logic. It is a cornerstone of logical reasoning in SSC and Banking exams, rewarding those who can quickly map letters to their numerical positions.
Letter-to-Number Coding
This subtopic requires direct assignment of numbers to letters based on their alphabetical rank or specific key values. You must memorize positions instantly to save time during high-pressure sections.
- A=1, E=5, J=10, O=15, T=20, Y=25 (EJOTY rule)
- Reverse position = 27 - Direct rank
- Sum of digits approach
- Vowel/Consonant categorization
Letter-to-Letter Coding
Focuses on patterns like forward shifting, backward shifting, or cross-pattern encryption. Candidates must observe if the change is constant or progressive across the word.
- Forward/Backward shift pattern
- Cross pattern (e.g., swapping adjacent letters)
- Position-based reversal
- Addition/Subtraction arithmetic chains
Word and Sentence Coding
Commonly known as 'Chinese Coding', it involves finding common words across two or more sentences to deduce their specific code. Speed is gained by focusing only on the target word rather than decoding the whole sentence.
- Comparative elimination method
- Intersection of word sets
- Frequency count analysis
- Substitution based on comparative logic
Matrix and Clock-Based Coding
Matrix coding requires identifying letters from row-column coordinates. Clock-based coding involves shifting letters according to 12-hour or 24-hour cycle logic.
- Read row first, then column (R,C)
- Clockwise/Anticlockwise positional shift
- Digit cross-sum reduction
- Symmetry check in matrix grids
Formula Sheet
Alphabet position = N
Reverse position = 27 - N
EJOTY = 5, 10, 15, 20, 25
Exam Tip
Write the alphabetical ranks (1–26) and their reverse pairs on your rough sheet the moment the exam begins to avoid mental arithmetic errors.
Common Mistakes
- Miscalculating the reverse alphabetical rank by forgetting to add 1
- Failing to notice the pattern holds only for half the word length in cross-coding
- Spending too much time decoding every single word in sentence-based coding instead of just the query word
More Revision Notes
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