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| C programming language |
TheC programming language wasoriginally developed by Dennis Ritchieof BellLaboratories, and was designed to run on a PDP-11 with a UNIX operating system. Although it was originally intended to run under UNIX, there was a great interest in running it on the IBM PC and com- patibles, and other systems. C is excellent for actually writing system level programs, and the entire Applix 1616/OS operating system is written in C (except for a few assembler routines). It is an excellent language for this environment because of the simplicity of expression, the compactness of the code, and the wide range of applicability.
The C programminglanguage is excellent for actually writing system level programs, and the entire Applix 1616/OS operating system is written in C (except for a few assembler routines). It is an excellent language for this environment because of the simplicity of expression, the compactness of the code, and the wide range of applicability. One experienced C programmer made the statement, "You can program anything in C", and the statement is well supported by my own experience with the language. In C, you are very much on your own, as you will soon find.
Since C is not a beginners language, I will assume you are not a beginning programmer, and I will not attempt to bore you by defining a constant and a variable. You will be expected to know these basic concepts. You will, however, not be expected to know anything of the C programming language. I will begin with the highest level of C programming, including the usually intimidating concepts of pointers, structures, and dynamic allocation. To fully under- stand these concepts, it will take a good bit of time and work on your part, because they not particularly easy to grasp, but they are very powerful tools. Enough said about that, you will see their power when we get there, just don’t allow yourself to worry about them yet.
Programming in C is a tremendous asset in those areas where you may want to use Assembly Language, but would rather keep it a simple to write and easy to maintain program. It has been saidthataprogramwrittenin Cwill payapremium ofa50to 100%increase inruntime,because no language is as compact or fast as Assembly Language. However, the time saved in coding can be tremendous, making it the most desirable language for many programming chores. In addition, since most programs spend 90 percent of their operating time in only 10 percent or less of the code, it is possible to write a program in C, then rewrite a small portion of the code in Assembly Language and approach the execution speed of the same program if it were written entirely in Assembly Language. Apple Macintosh system software was formerly written in Pascal, but is now almost always written in C.
C is one of a large number of high level languages which can be used for general purpose programming, that is, anything from writing small programs for personal amusement to writing complex applications. It is unusual in several ways. Before C, high level languages were criticized by machine code programmers because they shielded the user from the working details of the computer, with their black box approach, to such an extent that the languages become inflexible: in other words, they did not not allow programmers to use all the facilities which the machine has to offer. C, on the other hand, was designed to give access to any level of the machine down to raw machine code and because of this it is perhaps the most flexible of all high level languages.
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