main() Method

1. Define main() function?
   View Answer
   
   
   main() is a compiler declared function whose defined by the user, which is invoked automatically by the operating system when program is being executed.
   
   
2. What is the default prototype of main() function?
   View Answer
   
   
   Default return of a main() function is int and default parameter is void.
   int main(void){
       //body
       return 0;
   }
   
   
3. What are the arguments of main() function?
   View Answer
   
   
   int main(int argc, char *argv[], char * env[]){
       //body
       return 0;
   }
   A main() function has 3 arguments:
   

   1. argc (Argument Count) - Stores number of command-line arguments passed by the user including the name of the program.
   2. argv (Argument Vector) - It is an array of strings which stores values which are passed from command-line.
   3. env (Environment Vector) - It contains all environmental variables of the system.
   
   
4. What is the use of return statement in main() function?
   View Answer
   
   
   A return statement in main() function tells to compiler about type of termination. The return value is 0(zero) means normal termination and return value is non-zero means abnormal termination.
   
   
5. Is it possible to execute user defined functions before and after main() function in C?
   View Answer
   
   
   #include<stdio.h>
   void before_main();
   void after_main();
   #pragma startup before_main
   #pragma exit after_main
   void before_main(){
       printf("Before main() function.\n");
   }
   void after_main(){
       printf("After main() function.\n");
   }
   int main(){
       printf("Inside main() function.\n");
       return 0;
   }
   Note:The above code executes in Turbo C compiler, doesn't in GCC compiler.
   
   
   

Next