【正文】 grams. Assembly language programs are often less than onehalf the size of parable HLL programs. This is especially impressive when you consider the fact that data items generally consume the same amount of space in both types of programs, and that data is responsible for a good amount of the space used by a typical application. Saving space saves money. Pure and simple. If a program requires megabytes, it will not fit on a Mbyte floppy. Likewise, if an application requires 2 megabytes RAM, the user will have to install an extra megabyte if there is only one available in the machine. Even on big machines with 32 or more megabytes, writing gigantic applications isn39。 even greater improvement is possible if you39。t impress those who know the truth. 2 What39。t pile and run on a Macintosh. And even if they did, most Mac owners wouldn39。s still too slow? This is a totally bogus argument against assembly language. Any algorithm you can implement in a HLL you can implement in assembly. On the other hand, there are many algorithms you can implement in assembly which you cannot implement in a HLL. Assembly language is not portable. This is an undeniable fact. An 80x86 assembly language program written for an IBM PC will not run on an Apple Macintosh. Indeed, assembly language programs written for the Apple Macintosh will not run on an Amiga, even though they share the same 680x0 microprocessor. If you need to run your program on different machines, you39。t you use this better algorithm in assembly language? What if you39。s why you use C 4 pilers. Today, machines are so fast that we no longer need to use assembly. It is amazing that people will spend lots of money to buy a machine slightly faster than the one they own, but they won39。t true and probably never will be true. Optimizing pilers are getting better every day. However, assembly language programmers get better performance by writing their code differently than they would if they were using some HLL. If assembly language programmers wrote their programs in C and then translated them manually into assembly, a good C piler would produce equivalent, or even better, code. Those who make this claim about piler technology are paring their handpiled code against that produced by a piler. Compilers do a much better job of piling than humans. Then again, you39。s a skill you develop through experience. Assembly language is hard. This statement actually has a ring of truth to it. For the longest time assembly language programmers wrote their programs pletely from scratch, often reinventing the wheel. HLL programmers, especially C, Ada, and Modula2 programmers, have long enjoyed the benefits of a standard library package which solves many mon programming problems. Assembly language programmers, on the other hand, have been known to rewrite an integer output routine every time they need one. This book does not take that approach. Instead, it takes advantage of some work done at the University of California, Riverside: the UCR Standard Library for 80x86 Assembly Language Programmers. These subroutines simplify assembly language just as the C standard library aids C programmers. The library source listings are available electronically via Inter and various other munication services as well as on a panion diskette. Assembly language programming is time consuming. Software engineers estimate that developers spend only about thirty percent of their time coding a solution to a problem. Even if it took twice as much time to write a program in assembly versus some HLL, there would only be a fifteen percent difference in the total project pletion time. In fact, good assembly language programmers do not need twice as much time to implement something in assembly language. It is true using a HLL will save some time。ll have problems debugging programs in that language until you gain experience. 3 Assembly is hard to maintain. C programs are hard to maintain. Indeed, programs are hard to maintain period. Inexperienced assembly language programmers tend to write hard to maintain programs. Writing maintainable program