How to make dos win(8661251) converter?

Question

C++ / C#

There is an input file .txt either in MSDOS encoding or WIN, you need to recode the input file into a different encoding and output it to txt, everything is specified by the user. I can’t figure out how to use encoding tables. characters, which I then find in a different encoding, but I don’t know how to search in a different encoding (character table), that is, how to use different encoding tables. Ready-made libraries are not interested. It is necessary to implement the conversion algorithm.

Answer 1

https://msdn.microsoft.com/en-us/library/8w60z792.aspx