Complex sentence: Over a long period a form of shorthand notation developed as the parsers in early versions improved and generally if the assembler can determine the size of the data the data size specifier is not necessary although it still can be used.
Split into simpler sentences: Over a long period a form of shorthand notation has developed as the parsers in early versions improved. Generally the data size specifier is not necessary if the assembler can determine the size of the data, although it still can be used.