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This chapter will
• Introduce you to the concept of Coding–Decoding.
• Expose you to various kind of logic involving in coding–decoding like Letter coding, Direct letter coding, Number/ Symbol coding, Substitution coding, deciphering message words code etc.
• Illustrate the application of each of these types.
• Test you on the understanding of these unexplored aspects by small exercises followed by exhaustive and comprehensive explanations.
Coding–or–encoding is the process of making a concept or idea understandable to others.
Decoding is the process of interpreting information that was coded by someone else.
The codes are based on various principles/patterns so that the message can be easily deciphered to the other end. To judge the intelligence and mental ability of an individual, such questions are asked in various competitive exams. The candidate is required to encode and decode words and sentences after observing the pattern and principles involved.
These questions can be broadly classified into 5 main categories, as follows:
(1) Alphabet (Letters) Coding Decoding
(2) Numer Coding Decoding
(3) Mixed Coding Decoding
(4) Coding by Subsitution
(5) Deciphering Messages
In this category, the questions are generally based on the letters of the English alphabet. A letter or a group of letters is given and a corresponding group of letters is also given. In other type of questions, a coded letter or a group of letters is given and you might be asked to find out or decode this coded letter or the group of letters. This coding or decoding process always follows a specific pattern. You have to find out that specific pattern coding to choose the correct answer.
It can be further be divided into two types:
In direct letter coding, the code letters occur in the same sequence as the corresponding letters occur in the word.
Example 1: In a coding language ‘STABLE’ is written as ‘BDFGJK’ and ‘FORTUNE’ is written as ‘MOXDYZK’, then how is ‘STONE’ written in that code?
Solution: Observing the given words and code, we can find that:
(I) There is no apparent rule governing the coding.
(II) Both the given words have common codes corresponding to common letters i.e. ‘STABLE’ and ‘FORTUNE’ have TE in common in the word and ‘DK’ is common in the code. This shows that the code letter is in the same sequence as the corresponding letters in the word.
(III) STONE is formed by a combination of letters of STABLE and FORTUNE. Thus all the above three arguments indicate that this is a question of direct–coding.
For the given word, we have
Thus, the code for STONE becomes BDOZK.
Example 2: In a defense message, GET AWAY, FIRE BACKWARD, MOVE SLOW is coded as BEN CDCI, QHOE PCTL DCOX, ZMWE VFMD. Based on this coding system, find the code for the following words:
Solution: Observing the given message, we find that as such no definite rule of coding seems to follow. Also, whenever. A occurs in the message, C comes at the corresponding place in the particular code. This is direct coding.
1. The code for OVER is MWEO.
2. The code for DEADLY is XECXFI.
3. The code for REWARD is OEDCOX.
4. The code for GREAT is BOECN.
In these questions, the letters in the word are replaced by certain other letters according to a specific rule to form its code. The candidate is required to detect the coding pattern/rule and answer the question accordingly. The difference between Type 2 questions and Type 1 questions is that a student needs to find a specific pattern in Type 2 questions whereas in Type 1 questions, a pattern is given and a direct answer is available by merely looking at the pattern.
These rules/patterns can be classified as:
Here, a word is coded by increasing/decreasing the corresponding numerical value of the alphabet.
Example 1: In certain code language, FATHER is written as HCVJGT. How is STUDENT written in the code?
Solution: In the word FATHER and its code HCVJGT, we find that each letter in the word FATHER is moved two steps forward to obtain the corresponding letter of the code i.e.
Similarly, we can find the code for STUDENT, i.e.
Hence, the desired code is UVWFGPV.
Example 2: In a certain, the word LOUD is coded as JMSB. Following the same rule of coding what should be the word for the code PGQC?
Solution: Here each letter of the word is two steps behind the corresponding letters of the code. i.e. .
Following the similar pattern, the word for the code PGQC will be
Hence, the required answer is RISE.
Example 3: In a certain code, ALMIRAH is written as BNPMWGO, which word would be written as QTLRYKY?
Solution: Here, when we compare ALMIRAH with its code BNPMWGO, we find the first letter of code ‘BNPMWGO’. Similarly, 2nd letter of code is 2 steps ahead and so on.
Hence we find the word for code QTLRYKY is PRINTER.
In these questions, a word is coded by simply changing the order of letters of the word. The candidate is required to detect the coding pattern and answer the questions accordingly.
Example 1: In a code language if BASIC is coded as CASIB, how will DANCE be coded in the same language?
Solution: If we compare BASIC with CASIB, we can see that the letters used in the code and the word are same but their order of placement has been changed. Letter B at the first position of basic word has been placed at fifth position in the coded word and letter at fifth position in the word BASIC has been placed at first position. The position of second, third and fourth letters remain unchanged.
So, DANCE can be coded as EANCD.
The following two tables are used to solve this type of questions.
CORRESPONDING LETTERS (I)
CORRESPONDING LETTERS (II)
Example 1: In a certain language ‘SERVICE’ is written as HVIERXV. How is ‘WORKER’ coded as?
Solution: Every letter a corresponding letter i.e.,
Similarly, we can find the code for the word WORKER, i.e.,
Hence, desired code is DLIPVI
Here, such questions are asked where the letters of the given word are jumbled according to a certain rule to generate the code.
Example 1: In a certain code HARVEST is written as TSEVRAH. How will CASTE be written in that code language?
Solution: Here HARVEST is written as TSEVRAH. The order of letters has been reversed in the code. Similarly, CASTE will be written as ETSAC.
Example 2: In a certain code HEALTH is written as GSKZDG, then how will NORTH be written in the same code?
Solution: Here as we notice word HEALTH and its code GSKZDG, we can see the letters of the given word are written in a reverse order. Then each letter is moved one step backward to obtain the code.
So following the same pattern, we will reverse the order of letter in NORTH, we will get HTRON. Now moving each letter of word HTRON, one letter backward, ie.,
So, the required code is GSQNM.
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