What is the difference between binary and ASCII based file comparison?

Question

If I use a file comparison tool like fc in Windows, you can choose between ASCII and binary comparison.

What is the actual difference between these two comparisons? If I compare two ASCII files, don't I want the binary data of the files to be identical?

Answer 1

WARNING: this is 5 year old loose remembrance of knowledge from uni

Binary representation means you compare the binary exactly, and ascii is a comparison of data type. to put it in a simple case the char 'A' is a representation of 01000001, but that is also an 8 bit integer equal to '65', so that means A = 65 in binary. so if you were doing A + A as a string and 65 43 65 (43 is '+' in binary to decimal), in binary they would be equivalent, but in ascii they would not. This is a very loose explanation and i'm sure i missed a lot, but that should sum it up loosely.

In a text file you want ASCII because you write in ascii characters. In say, a program state saved to a file you want binary to get a direct comparison.