Coding–decoding (new pattern) for IBPS PO

Coding–decoding used to mean "each letter moves one step forward". In IBPS PO today you are more likely to meet a set of coded sentences, a word changed in two steps, or a table of codes with conditions that swap them. Each form has a fixed way in, and none needs guesswork.

The skill underneath all of them is the same: test a rule on one part, confirm it on every part, and only then apply it.

The letter table you need

Know letter positions without counting on your fingers.

• EJOTY marks 5, 10, 15, 20 and 25. From E (5), F is 6; from O (15), M is 13.
• Opposite letters add to 27: A–Z, B–Y, C–X, D–W, E–V, F–U, G–T, H–S, I–R, J–Q, K–P, L–O, M–N.
• Moving past Z wraps round to A: Y + 3 is B.

Type 1: sentence coding

Each word always has the same code, but the codes inside a sentence may be in any order. Compare sentences that share words.

Worked example 1

• "bank loan rate high" is coded "pa ki lo mu"
• "loan is easy now" is coded "ki ta ne ro"
• "rate is low today" is coded "lo ta su zi"
• "easy bank today" is coded "ne pa zi"

Solving

• "loan" is in sentences 1 and 2. The only common code is ki.
• "rate" is in 1 and 3: common code lo.
• "bank" is in 1 and 4: common code pa.
• Sentence 1 has one word left, "high", and one code left: mu.
• "is" is in 2 and 3: ta. "easy" is in 2 and 4: ne. "today" is in 3 and 4: zi.
• Leftovers: "now" is ro, and "low" is su.

If a word appears only once and its sentence still has two unsolved words, the code cannot be determined. That is a legitimate answer option; do not guess.

Type 2: step rules

The word is changed by a fixed set of steps. The steps must be undone in reverse order to decode.

Worked example 2: split, reverse, shift

Rule: split the word into two halves, reverse each half, then move every letter one step forward.

• PLANET → halves PLA and NET.
• Reverse each half: ALP and TEN.
• Shift +1: A→B, L→M, P→Q, T→U, E→F, N→O.
• Code: BMQUFO.

To decode, shift −1 first, then reverse each half.

Worked example 3: a varying shift

In a code, CODE is written DQGI. What is the rule?

• C (3) → D (4): +1. O (15) → Q (17): +2. D (4) → G (7): +3. E (5) → I (9): +4.
• The shift grows by one for each letter. Test a rule on every letter before you trust it; a rule that fits only the first two letters is not the rule.

Type 3: opposite letters

Each letter is replaced by its opposite.

Worked example 4

BANK: B (2) → Y (25), A (1) → Z (26), N (14) → M (13), K (11) → P (16). Code: YZMP.

A quick check: the two positions always add to 27.

Type 4: condition-based coding

This is the "new pattern" form. You get a table of codes and a list of conditions that change the codes for certain words.

Worked example 5

Vowels here are A, E and U.

• Condition (i): if the first letter is a vowel and the last is a consonant, both are coded as the code of the last letter.
• Condition (ii): if the first and last letters are both consonants, their codes are interchanged.
• Condition (iii): if the first letter is a consonant and the last is a vowel, the last letter is coded as &.
• If no condition applies, use the table as it is.

Questions

1. BRAKE: consonant first, vowel last, so condition (iii). Code: # $ 4 2 &.
2. AMBTRK: vowel first, consonant last, so condition (i); both ends take K's code 2. Code: 2 @ # 3 $ 2.
3. PUNTER: both ends consonants, so condition (ii); P and R swap codes. Code: $ 8 9 3 7 5.
4. UMBERA: vowel first and vowel last, so no condition applies. Code: 8 @ # 7 $ 4.

Common mistakes

• Trusting a rule after one letter. Confirm it on every letter.
• Decoding in the wrong order. Undo the last step first.
• Forgetting to wrap past Z in a forward shift.
• Assuming code order matches word order in sentence coding. It usually does not.
• Answering a sentence-code question that has no unique answer. Look for "cannot be determined" in the options.

Practice set

1. Using worked example 1, what is the code for "high"?
2. Using worked example 1, which word is coded "su"?
3. Using worked example 1, what is the code for "now easy bank"?
4. Using the rule in worked example 2, how is MARKET coded?
5. Using the same rule, which word is coded TJTSFU?
6. Using opposite letters, how is COW coded?
7. Using worked example 5, how is TUBNEK coded?
8. Using worked example 5, how is EBNAUT coded?

Answers

1. mu. It is the one code left in sentence 1 after loan, rate and bank are solved.
2. low. The one word left in sentence 3 after rate, is and today.
3. ro, ne and pa, in any order, since order inside a sentence code is not fixed.
4. SBNUFL. MAR and KET reversed are RAM and TEK; shifting +1 gives SBN and UFL.
5. SISTER. Shift −1: SIS and RET. Reverse each half: SIS and TER.
6. XLD. C (3) ↔ X (24), O (15) ↔ L (12), W (23) ↔ D (4).
7. 2 8 # 9 7 3. T and K are both consonants, so their codes (3 and 2) swap.
8. 3 # 9 4 8 3. E is a vowel and T a consonant, so both ends take T's code, 3.

What to do next

• Write the EJOTY positions and the 13 opposite pairs from memory until both take under a minute.
• Solve one sentence-coding set and one condition-based set a day for a week.
• Revise order, ranking and alphanumeric series, which uses the same careful symbol counting, and input–output, where rules are also found by testing steps.