Coding-Decoding for Bank Exams | Approach and Important Tips

Coding and Decoding is a common topic in the Reasoning section of bank exams. The most basic type of this topic is to find the code of a given word. There are a few types of Coding and Decoding questions which we will discuss with examples for a better understanding of the topic.

Coding and Decoding: The Concept

Coding is a process used to convert a word or a number or sometimes a mixture of both into a code based on some pattern or conditions. Decoding is the process of retrieving the word or number from the given codes. The codes are generally constituted of letters or numbers or sometimes a mixture of both. Usually, one or two words and its/their respective codes are given in the question and we need to determine the code of another word which will follow the same logic or pattern to form its code.

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The Approach while attempting any Coding and Decoding Question

  • The first thing while attempting any question of this topic is finding the hidden pattern or logic in the formation of the codes.
  • While solving the question, decoding the relations between the two terms: the given word and its code should be done first.
  • Be thorough with the letters of the alphabet. In case of only number coding, always try to find a logical deduction of the numbers from the letters.
  • Have a step by step approach to Coding and Decoding questions. Check the code and deduce the pattern. It is not necessary that the pattern will be clearly visible as soon as you see the code. Try and match the pattern/logic by arranging and rearranging the letters of the code.
  • In case of substitution type, match the codes with the corresponding letters/words by the number of times a letter/word and code appears.

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The Major Types of Coding and Decoding Questions

1. Letter Coding

The letters in a word are replaced by other letters following a specific pattern to form its code.

Let us look at an example:

Example 1: The word ‘FAUCET’ is coded as ‘GBWEHW’ in a certain code language. In the same language, ‘CODING’ will be coded as ___.

So, we first try to find the pattern followed in the formation of the code.

We see that the immediate next letter of F in the alphabet is G and so is the letter B for A, i.e., F + 1 = G and A + 1 = B. But the third letter of the word U is coded as W. W is two positions ahead of U in the alphabet, i.e., U + 2 = W. Counting the rest of the letters in the code, we get that:

C + 2 = E

E + 3 = H

T + 3 = W

So, the pattern followed for the 6-letter word is +1, + 1, +2, +2, +3, +3 consecutively.

Following the same pattern, the required code is:

C + 1 = D

O + 1 = P

D + 2 = F

I + 2 = K

N + 3 = Q

G + 3 = J

Answer: DPFKQJ

Example 2: The word ‘ABRUPT’ is coded as ‘FKGZYI’ in a certain code language. In the same language, ‘MODEST’ will be coded as ___.

When the letters of the alphabet are counted in normal order (starting from A) and in reverse order (starting from Z), then A and Z have the same ranks (1), B and Y have the same ranks (2), C and X have the same ranks (3), and so on.

In this code, all the letters are not coded serially. The word is first split into two, i.e., ABR and UPT and their positions are interchanged and then they are coded:

ABR UPT = UPT ABR = FKG ZYI

Hence, required code: MOD EST = EST MOD = VHG NLW

Answer: VHGNLW

 

NOTE: There is always a common and systematic pattern in basic letter coding. One of the patterns is generally adding a few positions or subtracting a few positions from a letter like we saw in Example 1. The other pattern is through the ranks of the letters in the alphabet like in Example 2. Some questions might also add/subtract positions from a letter based on whether it is a consonant or a vowel. Most questions will be based on these patterns without or with shifting the positions of the letters (in reverse order or splitting into two, etc). Also, the patterns are systematic: we are more likely to come across a pattern such as +1, +1, +1, and so on or +2, -2, + 2, -2, and so on  or +1, +2, +3, and so on rather than a random pattern such as +2, +7, +5, +1, +4, +3, etc.

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2. Number or Symbol Coding

This type is very similar to the first type. Instead of letters, the codes are generally in numbers or symbols. We derive the code for each letter based on the given codes.

Example 3: In a certain code language, the word ‘WORDS’ is coded as ‘3#51@’ while ‘SEAR’ is coded as ‘@9!5’. How will ‘DARE’ be coded in the same language?

From the given words, we get:

S and R are common, S = @, R = 5. The codes of the rest of the letters are:

W = 3, O = #, D = 1

E = 9, A = !

So, DARE = 1!59

Answer: 1!59

NOTE: Unlike letter coding, in number and symbol coding, the codes for each letter should be matched in questions like Example 3. However, in some questions, there might be only numbers that have to be derived based on the ranks of the letters in the alphabet.

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3. Coding by Substitution

In this type, the words in a sentence are substituted by other letters/words/numbers/symbols.

Example 3: In a certain code language, “an endemic is disease” is coded as “pu bt ys ej”, “any disease is curable” is coded as “ar bt xw ej” and “any endemic is not epidemic” is coded as “ys ar mo bt hz”.

1) How is ‘curable’ coded?

2) Which word is coded as ‘mo’?

We have,

(i) “an endemic is disease” is coded as “pu bt ys ej”

(ii) “any disease is curable” is coded as “ar bt xw ej”

(iii) “any endemic is epidemic” is coded as “ys ar mo bt”

Comparing (i), (ii) and (iii), we have

is = bt

Comparing (i) and (ii), we have

disease = ej

Comparing (i) and (iii), we have

endemic = ys

Comparing (ii) and (iii), we have

any = ar

Now from the remaining words and codes, in (i): an = pu

In (ii): curable = xw

In (iii): epidemic == mo

Answer: 1) ‘curable’ is coded as ‘xw’.

2) ‘epidemic’ is coded as ‘mo’.

NOTE: The basic idea in this type is the frequency of the words and codes. If a word appears three times in the whole para, we match it with the code that appears thrice. We keep doing so until we get all the codes. In most exams, coding and decoding by substitution come as a set of 3-5 questions with 3-6 coded sentences while some exams may have them as individual questions. Read the whole question thoroughly and note down the codes while doing so.

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4. Coding through Advanced Logic

This type of Coding and Decoding questions generally come in only Mains level examinations. The codes are formed using advanced logic, like the number of letters/vowels/consonants in a word, replacing certain letters of a word or coding certain letters as symbols, etc.. As the questions of this type are of higher level, we will discuss them later.

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All Things Considered

Coding and Decoding is an easy topic in the Reasoning Section and usually, there are 1-6 questions in any exam. Practise as many questions on this topic to have a good grasp of it.

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