C Warning Implicit Declaration Of Function 'exit'

Answer :

Add:

#include <stdlib.h> 

to the top of your program.

Do you have this preprocessor? If not, add it.

#include <stdlib.h> 

exit() is a library function, the respecive prototypes are present in the stdlib.h header file, inoder to call the process to specified code for exit function, you need to attach the as #include stdlib.h header in your program. that is the reason we should add the stdlib.h header. eventhough you can run the program, but it shows the warning message like below:

warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default]       

but, this kind of program not recommended, we need to take care of what we are given in the program,be cautious. warning may leads runtime error.