# Coding and Decoding - Concept and different models of Coding and Decoding Questions

## Coding and Decoding  - Shortcuts

Code : A code is a a system of words, letters, figures, numbers or symbols used to represent a message or record information  especially for the purposes of secrecy or in a shorter form
Coding : A system of signals used to represent letters or numbers in transmitting messages. It is is a method of transmitting a message between the sender and the receiver such that no other person can understand the message. We can also call this process as encoding
In coding, actual letters/ numbers / words/ symbols are replaced by certain other letters/numbers/words/symbols etc.
To solve the question on coding, students have to detect (find ) the rule used in the coding and then answer the question
Decoding : Decoding is the reverse of encoding. It is a method of finding the meaning of something that has written in the code.

Kinds of Coding- Decoding questions:

Letter Coding :
Method of Letter Coding:
a)   Skipped over the letter in forward and backward direction
Example: The word ‘SECRET’ is coded as ‘TFDSFU’. How will ‘TRANSMIT’ be coded ?
Explanation: Here compare each letter of word and coded word.
S+ 1 =T  E+1=F   C+1=D  R+1=S E+1=F and T+1 =U
In the same way, TRANSMIT will be coded as
T+1=U  , R+1=S ,A+1=B , N+1=O , S+1=T , M+1=N , T+1=U
So , TRANSMIT will be coded as USBONU
Example 2 : In a certain language, KAKINADA is coded as JZJHMZCZ . How is ANDHRA is coded in that language?
Explanation: Clearly, we can see that each letter of the word KAKINADA is moved one step backward to get the the code.
K-1 = J , A-1= Z , K-1=J ,  I-1=H, A-1=Z , D-1=C , A-1=Z
Similarly, ANDHRA is coded as => A-1=Z, N-1=M , D-1=C, H-1=G,R-1=Q , A-1=Z
SO ANDHRA will be codes as ZMCGQZ

b)   Writing the letters of given word in reverse order in part or in whole.
Example : In a certain code language, SHARMA is written as AMRAHS. How will VASUDHA be written in the  code?
Explanation : Clearly, when SHARMA is coded, all letters are revered.
Similarly the code word for VASUDHA is AHDUSAV.
Example 2 : In a certain code, SUDHEER is DUSHREE . What is the code word for SRAVANI?
Explanation : Here in this coding and decoding questions, SUDHEER is written as DUSHREE.
Clearly, we can observe first 3 letters are reversed , middle letter kept in the same place and last three letters are reversed.
Similarly , the first three letters are SRA are reversed as ARS , middle letter kept as before and last 3 letters ANI are reversed INA.
So the code word for SRAVANI is ARSVINA

c)In few question of coding and decoding , codes may be the position of those letters in the alphabet
Example : In certain language, EARN is coded as 511814. What is the code for SICK in the same language ?
Explanation: Here , the position of each letter in alphabet is written as code.
The position of E is in the alphabet is 5 , A=1 , R=18 and N=14.
Similarly, the code word for SICK is , S=19 I=9 C=3 K=11
The code word for SICK is 199311

Number Coding :
Number coding and decoding involves two kinds of cases

a)   Numerical code values are assigned to a word.
Example : If C=3 , BAT=23 then the code for RAHUL?
Explantion: Clearly in the given code, C=3 . So position of the letter in the alphabet is written
BAT = 23 => B =2 , A=1 and T=20. All positions are added  2+1+20 =23
Similary , RAHUL = 18 + 1 + 8+21+12 =60
Therefore, the code for RAHUL is 60

b) Alphabetical code letters are assigned to the numbers
Example : In a certain code 17286 is written as AIBZJ and 3459 is written as YGUN. How is 12345 is written in the code?
Solution : Here letters are assigned to each number.
From the first one         1=>A , 7=>I , 2=>B , 8 =>z , 6=>J
And from the second one 3=>Y, 4=>G, 5=>U  and 9=>N
The in the same coded language , 1=A , 2=B , 3=Y  , 4=G and 5=U
Therefore , the 12345 is written as ABYGU in the code language.

Substitution Coding :
In these type of coding and decoding reasoning questions, different objects are assigned code names.
Example: If Sky is called Earth , Earth is called Moon , Moon is called Pen ,Pen is called  River and River is called Sun. Which of the following is used for writing ?
a)Earth                   b)Pen            c)Moon                   d)River
Explanation: We know, pen is used for writing.
Here, pen is called River.
Therefore, River is used for writing in this code language.

Mixed Letter Coding:
In this kind of coding and decoding questions, three or more sentences are given in the coded language and the code for a particular word is asked. These sentence consists of 3 or more words .To find the code for particular word  ,take two sentences having a common word and the common code word will give that word. We can find the code word for each word of given sentences similarly.
Example : In a certain code language , “ dit par la” means “ I love you “, “par mat do “ means “ love is good” and “ ka mat par” means “ love is great”. In that language, which word stands for “ great”   ?
Explanation:
Take first two sentences, the common word is love and common code word is par.  So ‘Love ‘ stands for ‘ par’
In last two sentences , the code word ‘mat’ is common and the word ‘ is ‘ common , so is ‘stands’ for ‘mat’.
So , in the third sentence ‘ ka mat par ‘   , the remaining code word ‘ka’ stands for ‘great’