Hi,
I'm in complete disaccord with Andy. Probably, C is rather efficient in 166 or PIC18 or somewhere else but NEVER in 51! The internal architecture of 51 is so irregular that only assembler can gain effective code. Another myth is that writing in C is faster. It can be in certain cases, but never debugging in C is simpler. That is why mixing languages is a generally accepted practice. I think the question has already been discussed once on this forum some time ago?
Michael.