Coding and Decoding

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Theory

Coding and Decoding questions are generally asked to test logical reasoning ability. Coding is a way to convert a word or sentence into another language of words and numbers whereas decoding is to convert back the coded value into its normal language.
In these type of questions, a coded form is generally given to the student and he has to find logic behind this conversion. After understand the logic behind the code, you are asked to either code or decode another word.

Tip

Remembering English alphabets with their corresponding number value will help you a lot in this section. The position of a letter in english alphabet is considered to be its numerical value. Hence, A=1 and Z=26.

Tip

The numbering system of alphabets is cyclical in nature i.e. we consider A to come after Z. Hence, A (value=1) changes to D(value=4) then Z (value=26) changes to C (value=26+3-26 = 3).

Tip

The word EJOTY helps to find the position of a word in alphabet.

E J O T Y
5 10 15 20 25

For example: if we want to find the position of letter “S” in alphabet series, we know that T’s number value is 20, so S’s position will be 20-1=19.

Theory

Generally 3 types of questions are asked in this section.

1. Letter to letter
2. Letter to Number
3. Miscellaneous Types

In letter to letter, a letter is coded in the form of another set of letters. In Letter to Number, a letter is coded in the form of a set of numbers and in miscellaneous types a set of letters/numbers can be coded in various types of sentences.

Solved Example

In a certain coded language, “dog” is written as “dg”, “boats” is written as “bost”, “shocked” is written as “edhkos”, “republicans” is written as “abceinprsu”

What is the code for: “friends”?
a)nifdsr
b)dfines
c)dfinrs
d)srnifd
e)srnfdi

Answer: C

Solution:
From the examples, we can see that the coded word is formed by dropping the middle letter from the original word and arranging the remaining letters in alphabetical order. So, for the word “friends”, the coded form is “dfinrs”.

Solved Example

If the word “qwerty” is coded as “pvdqsx”, then what is the code for “lunchbox”?

a)ktbmwang
b)ktmbganw
c)mtkbganx
d)lmtkbanx
e)None of the above

Answer: Option B

Solution:
Each letter is replaced by its previous letter. So, the coded word for “lunchbox” is “ktmbganw”

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