Nowadays it’s an international standard (ISO/IEC 646). If you use ASCII characters from code 0 to 127 you are safe. But if you intend to use extended ASCII (8-Bit) up to code 256, the characters will differ from system to system.
Devam Kakdiya (Kratos)
ASCII means American Standard Code for Information Interchange, is a character encoding standard for electronic communication. And standard is a standard, it does not depend on language
Back in the bad old days of dos this was a nightmare! As Michael has pointed out the ASCII standard was originally defined for seven bit characters, so only the first 128 characters were defined. Extended ASCII was used to define the additional 128 characters from 128 to 255. These extended characters were language or region specific. This meant that different sets of characters were required for different languages, these sets were known as code pages.
If you received an 8 bit extended ascii file and didn't know what code page it was written in it could appear as random characters. This lead to the creation of various alternative encoding systems such as utf-8 and utf-16 and wide character support.
So while the original 1967 ASCII standard is the same on all systems it only applies to the first 128 character glyphs and control codes. These days most people will assume ASCII to mean Extended ASCII.
Try looking at old ms-dos era text files on Windows and you will often see accented characters surrounding blocks of text. This is because ms-dos used these extended characters for line drawing (box drawing) characters but windows used the same code numbers for accented European characters.