Hi,
The following is an example of file i have in ubuntu platform. Column 2 consists of reference strings with which strings from column 1 are compared. The symbols that denote the additional or lacking of characters can only be put on strings in column 1, when strings at the same row are compared across the 2 columns.

Note:
1) . (a full stop) denotes lacking of a character at the end of string.
2) .. (two full stops) denote lacking of 2 characters at the end of string and so on.
3)'' (apostrophe) denotes additional character(s) at the end of string.
4) This additional & lacking of characters only happen at the end of strings.
5) Range of the number additional/lacking (in my actual file) = 0 - 10
6) length of strings in my actual file = around 20

input:
Expected output
Can anyone provide me with scripts to solve this data processing. Thank you very much.

That sounds like something that would be better handled with a programming language that has a good range of string handling functions rather than a script.

What sort of output would you expect from comparing POP with PREPPER?

Hi psion10,
Thanks for the very good example for consolidating my question! For your information, all the strings in my actual file are "biological" strings that have higher number of identical characters in the pairs of strings. If you reread my original input, the length of strings in my actual file is around 20. The "expected" degree of similarity between the pairs of strings is 16. Expected means what i can confidently say about my actual file. Thank you again.

It sounds like you want a function that will find the largest substring that is common to both names and that you can assume that only one substring of that length will exist.

Exactly. Thank you.

So if you are requesting assistance, please show what you have tried and where you are stuck?

Sorry grail,
I haven't picked up any programming language yet.In this case, i will request for assistance next time.