C Programming In Steps

29 Pages 7130 Words

1. Introduction.
C is a computer language available on the GCOS and UNIX operating systems at Murray Hill and (in preliminary form) on OS/360 at Holmdel. C lets you write your programs clearly and simply it has decent control flow facilities so your code can be read straight down the page, without labels or GOTO's; it lets you write code that is compact without being too cryptic; it encourages modularity and good program organization; and it provides good data-structuring facilities.
This memorandum is a tutorial to make learning C as painless as possible. The first part concentrates on the central features of C; the second part discusses those parts of the language which are useful (usually for getting more efficient and smaller code) but which are not necessary for the new user. This is not a reference manual. Details and special cases will be skipped ruthlessly, and no attempt will be made to cover every language feature. The order of presentation is hopefully pedagogical instead of logical. Users who would like the full story should consult the "C Reference Manual" by D. M. Ritchie [1], which should be read for details anyway. Runtime support is described in [2] and [3]; you will have to read one of these to learn how to compile and run a C program.

We will assume that you are familiar with the mysteries of creating files, text editing, and the like in the operating system you run on, and that you have programmed in some language before.



2. A Simple C Program
main( ) {
printf("hello, world");
}

A C program consists of one or more functions, which are similar to the functions and subroutines of a Fortran program or the procedures of PL/I, and perhaps some external data definitions. main is such a function, and in fact all C programs must have a main. Execution of the program begins at the first statement of main. main will usually invoke other functions to perform its jo...