Coding and decoding form an important part of the Analytical reasoning section in all the aptitude related papers. Usually, three to five questions appear from this area in various entrance exams.
In the alphabetic coding and decoding area, the majority of the questions are of the following types:
1. Pattern-Based Coding and Decoding: To solve pattern-based questions quickly, you should learn the positions of the letters in English alphabet. For this, you should learn the basic five letters of the non-dictionary word E-J-O-T-Y which are respectively positioned at 5, 10, 15, 20 and 25th position. With these five 'landmarks', the positions of all the other letters can be easily found. Let us take the case of 'R'. Since R is two letters behind T, so its position will be 18.
Example 1: The questions covered in this type are like "If TEACHER is coded as VGCEJGT, how will you code HUSBAND"?
Solution: Here, you need to check what logic of coding is applied between the letters of the given word and that of the code. Here code for T is V i.e. 2 is added in the position of T to get its code. The same thing happens for the other letters too. Now, to write the code of the word HUSBAND, you need to add 2 in the positions of the letters of the HUSBAND and its code will be JWUDCPF.
In the above example, suppose the code of the word TEACHER is TGJECVG. Here, the basic concept in coding is the same as the earlier one, the only difference is that the code is written in the reverse order.
Similarly, the difference in the letters of the word and the code may vary. E.g. the code for the word TEACHER could have been UGDGMKY, then the letters are moved + 1, + 2, + 3, + 4, + 5, + 6 positions.
Example 2: If the code of the word TEACHER is XHDIKHL, what will be the code of HEAT?
Solution: Observe the question closely and you should be able to conclude that there is no relation between the letters of the word TEACHER and the letters of the given code, but the letters of the word HEAT are already contained in the parent word TEACHER. So, picking the corresponding code from the parent word, the code for HEAT will be KHDX.
3. Coding of a word in a sentence: In this type of coding questions, generally three or four sentences or words are given with sentences or words containing codes. You just have to check for the common words/letters in the sentences/words and corresponding common words/letters in the codes to get the answer e.g. "Ram is Smart" is coded as LPG and "Smart means intelligent" is coded as SLY. From this, you should analyze that the only common word is 'smart' and the only common letter is 'L', which means that 'L' is the code for the word 'smart'. In such cases, the codes are not seen at the corresponding positions but for the common words.
