Here is the starting point for most of the C programs we are going to write,

int main(int argc, char** argv) {
    return 0;
}

Stepping through this program, we start with int which indicates that we are going to return an integer at the end of our program. When we compile and run our program in the terminal, we can see the integer that was returned. Assuming your C program is named test.c,

$ cc test.c
$ ./a.out
$ echo $?
0

Next, we have main. When you run a C program, it starts by finding the function named main and then executing the code inside.

main traditionally has two “arguments” or “inputs”. The first is an int named argc for “argument count”. The second is an array of char* named argv for “argument vector”. We’ll come back to char** in a bit because we don’t have to tools to explain it yet. But, conceptually, argc and argv correspond to the count and value of the arguments passed into the program from the command line.

$ ./a.out
# argc = 1
# argv[0] = ./a.out

$ ./a.out arg1 arg2
# argc = 3
# argv[0] = ./a.out
# argv[1] = arg1
# argv[2] = arg2

After the argc and argv arguments comes an opening brace {. Everything from { to its matching close brace } is called the “body” of the function. The body contains the code that gets executed whenever the function is run.

In our case, the body of main is just return 0. return stops execution of the body and sends the value out of the function. The value returned from main is often called the “return code” or “exit code” of the program because it is the final result of executing the program. Once a value is returned from main, the program is complete.

Finally, we have the closing } to indicate the end of the main function.