Late reply; sorry. > Date: Thu, 24 May 2007 08:43:26 -0700 > From: Les <hlhowell@xxxxxxxxxxx> > Embedded applications today > are mostly 8 bit, but many, many designers have already begun the > transition to 16 bit, and soon > will be moving to 32 bit. The reasons are much the same as > the reasons > that general computing has moved from 8 to 16 to 32 and now > to 64, with > the cutting edge already > looking at 128 bit and parallel processing, along with dedicated > processors running 32 or 64 bit floating point math. Also > the length of > the integer used in C, which is a virtual > machine is independent of the word length of the processor, > except the C > language designers (originally Kernigan and Ritchie) made the language > somewhat flexible to simplify migration. That is why there were some > undefined situations in the original specification. Remember > that C is > a virtual machine language, whose processor only has 24 > instructions (I > think the Ansi committee added a couple, but they have specific uses > that were not foreseen in the original usage of the language) > It can be > ported to any machine currently extant by only writing about 1K of > machine code, and even that can be done in another available higher > level language if you so desire, as long as it is compiled for > efficiency. Having used C since the original K&R version, I have to ask WHAT?!? Since when is C a virtual machine language? The only CVM I can find is Java's JVM. They have modified gcc (a C compiler) to produce byte code for that JVM. Every compiler I've used compiles C to native machine code for the target platform. There is no intermediate language, and that's what gave C its famous speed. (and because it is a virtual machine language...) > That is why even the 8 bit implementations of C used a 16 bit > integer. No it's not. They used 16 bit integers because you can't do much of anything useful with only 8 bit integers. The compiler designers for those systems (like the Apple II) had to work around the 8 bit registers. Looking at the assembly-language source for some of the libraries was not pleasant. Chris
