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Xiaobian to share with you how to use the main function in the c language, I believe most people still do not know how to use, so share this article for your reference, I hope you have a lot of gains after reading this article, let's go to understand it together!

The main function is the entry function of the C program, that is, the execution of the program starts from the main function, and the transfer of other functions is also directly or indirectly called in the main function.

The return value of the main function is used to interpret the exit state of the program.

If 0 is returned, the program exits normally. The meaning of other numbers returned is determined by the system. A non-zero return usually indicates an abnormal program exit.

Examples #include #include int main(int argc, char **argv) {int i = 0;printf("The program name is %s\n", argv[0]);printf("The command line has %d argument: \n", argvc - 1);for (i = 1; i < argc; i++) {printf("%s ", argv[i]);}return 0;}

Knowledge Point Expansion:

Every C program must have a main() function, which can be placed somewhere in the program according to your preferences. Some programmers put it at the front, others at the back, and wherever it is, the following points are appropriate.

During Turbo C2.0 startup, three arguments are passed to the main() function: argc, argv, and env.

* argc: integer, the number of command-line arguments passed to main().

* argv: String array.

char* argv[], we can see that argv is of type char* [], i.e. a pointer to an array of characters, so we can also write char** argv.

In DOS 3.X, argv[0] is the full pathname of the program run;

For DOS versions up to 3.0, argv[0] is an empty string (""). argv[1] is the first string after executing the program name on the DOS command line;argv[2] is the second string after executing the program name;...

argv[argc] is NULL.

*env: String array. Each element of env[] contains a string of the form ENVVAR=value. where ENVVAR is an environment variable such as PATH or 87. value is the corresponding value of ENVVAR such as C:\DOS, C:\TURBOC(for PATH) or YES(for 87).

TurboC2.0 always passes these three parameters to the main() function when it starts, and they can be stated (or not stated) in the user program. If some (or all) parameters are stated, they become local variables of the main() subroutine. Note: Once you want to specify these parameters, you must follow the order argc, argv, env, as in the following example:

main()main(int argc)main(int argc, char *argv[])main(int argc, char *argv[], char *env[])

The second case is legal, but less common, because there are very few cases where argc is used in programs without argv[]. The following is a sample program Example.EXE that demonstrates how to use three parameters in the main() function:

/*program name EXAMPLE.EXE*/#include#includemain(int argc,char *argv[],char *env[]){int i;printf("These are the %d command-line arguments passed to main:\n\n", argc);for(i=0; i

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