Coding-Decoding Questions for IBPS PO

Type 1: Letter Shift Coding

Each letter in a word is shifted by a fixed number of positions in the alphabet. For example, A shifts to D if the code is +3. The shift can be forward (toward Z) or backward (toward A). Some questions use opposite alphabet coding where A pairs with Z, B pairs with Y, and so on. This is the classic type and is becoming less frequent in IBPS PO but still appears as a warm-up question.

• Forward shift: each letter moves ahead by N positions. A+3 = D.
• Backward shift: each letter moves back by N positions. D-3 = A.
• Opposite alphabet rule: A=Z, B=Y, C=X. Sum of positions always = 27.
• Mixed shift: consonants shift one way, vowels shift another — watch for this trap.
• Always write out A=1 to Z=26 on rough paper first to avoid counting errors.

Type 2: Word/Sentence Substitution Coding

A full sentence is given in both normal and coded form. Each word maps to a code word (or symbol or number). You identify which code belongs to which word by comparing two or three sentences and finding which word appears in both sentences alongside which code. This is the dominant type in recent IBPS PO exams. The key skill is elimination: the word that appears in sentence 1 but not sentence 2 corresponds to the code that appears in coded sentence 1 but not coded sentence 2.

• Always compare at least two sentences to isolate one word-code pair.
• Common words between sentences = common codes between those coded sentences.
• The unique word in sentence 1 maps to the unique code in coded sentence 1.
• Order of words in the coded sentence may be scrambled — do not rely on position.
• Make a table: Word on one axis, Code on other. Cross out as you decode.
• Codes are usually 2-3 letter combinations or symbols — treat them as tokens, not letters.

Type 3: Number and Symbol Based Coding

Letters of a word are assigned numbers based on a rule (position in alphabet, reverse position, or a custom table). Sometimes a word is coded using only vowel positions, or consonants get one rule and vowels another. Symbols may replace numbers in final output. This type requires you to first identify WHAT rule maps letters to numbers, then verify with a second given example before answering.

• Check if numbers match A=1 to Z=26 (natural order) or Z=1 to A=26 (reverse order).
• Check if numbers are sums of letter positions (IBPS uses sum-coding rarely but it appears).
• Symbols often replace numbers in a fixed pattern: 1=@, 2=#, etc. Build the symbol table.
• Always verify your discovered rule against at least two given coded examples.
• If the code length differs from the word length, a letter is being dropped or doubled — look for that pattern.

Type 4: Conditional/New-Age Coding (IBPS PO Mains Focus)

A set of conditions is given: for example, if a word starts with a vowel, reverse the entire word code; if it ends with a consonant, add a symbol at the end. These questions combine two or three rules applied in sequence. This type is the hardest and appears in IBPS PO Mains. The trick is to process conditions in the stated order, one rule at a time, like following a recipe.

• Read all conditions first before coding any word — later conditions may override earlier ones.
• Write the base code first (using the letter-number table given), then apply conditions.
• Conditions often depend on the first letter, last letter, or word length — check all three.
• If two conditions could apply, usually only the first matching condition is used (unless the problem says otherwise).
• Practice elimination: if 3 answer options differ only in one position, you just need to figure out that one symbol.

• In sentence substitution, assuming the code appears in the same position as the word. Codes can be scrambled in order — always use elimination logic, not position.
• In letter shift coding, forgetting to wrap around the alphabet. T+10 is not the 30th letter — you must do mod 26, so T(20)+10=30, 30-26=4 = D.
• Confusing natural order (A=1) with reverse order (A=26) mid-solve. Once you pick a system, stick with it and verify with a second example before answering.
• In conditional coding, applying all matching conditions when only the first applicable one should be used. Always re-read the problem statement on this.
• Spending too long building the full decode table in sentence substitution when the question only asks for one word. Decode only what the question asks — save time.

• COPE rule for sentence substitution: Compare, Overlap, Pick unique, Eliminate. Two sentences share common words and common codes — the leftover pair is your answer.
• For opposite alphabet: think of the alphabet as a seesaw. A and Z balance at 27. B and Y balance at 27. Every pair sums to 27.
• For shift coding: CAESAR cipher — Julius Caesar used +3. If you see small shifts, think Caesar and test +3 or -3 first.
• For conditional coding: think of it as a checklist at airport security — go through each gate one by one, in order, and stop when you hit a rule that applies.

• IBPS PO Prelims 2022 and 2023 had sentence-substitution sets of 4-5 questions. This is your highest ROI type — master it first. You can solve a full set in under 2 minutes once you crack the logic.
• In Prelims, Coding-Decoding questions are usually moderate difficulty. Do not skip — they are more predictable than puzzle-grid questions and faster to solve with practice.
• If a set of 4 coding questions takes more than 3 minutes total, mark and move on. Do not let one stubborn code word eat into your Syllogism or Inequality time.
• Recent IBPS PO exams rarely ask plain letter-shift questions. If you see a simple shift question, it is likely a 30-second gift — take it and move on without overthinking.
• In Mains, coding questions may come as part of a mixed reasoning set. The conditional coding type needs calm, step-by-step approach — do these after you have secured easier marks elsewhere in the section.