When writing software in some cases we are not allowed to use Turkish characters so we use U, G, S, I, i, O, C characters instead of Ü, Ğ, Ş, İ, ı, Ö and Ç since some computer systems might not support Turkish character set. So in our software we use simple mapper to replace those characters with equivalent one. My question is how would you call this process? Transcription, transliteration or something else?
In general usage, transcription involves going from the sounds of a language to written symbols, and transliteration involves going from one set of written symbols to another.
Since you're starting with written symbols (in Unicode) and converting them to other written symbols (in ASCII), this would be transliteration. If you want to be more specific, call it "ASCII transliteration", or "lossy transliteration" (since it removes distinctions like
ı that the original writing preserved).