Main Function

Introduction

The main function is the entry point of every C program. OS calls main when the executable starts.

Understanding the topic

Signatures int main(void) or int main(int argc, char *argv[])

Return value return 0 for success; non-zero for error codes.

argc/argv Argument count and string array of command-line args.

• Signatures — int main(void) or int main(int argc, char *argv[]).
• Return value — return 0 for success; non-zero for error codes.
• argc/argv — Argument count and string array of command-line args.

Step-by-step explanation

1. Signatures — int main(void) or int main(int argc, char *argv[]).
2. Return value — return 0 for success; non-zero for error codes.
3. argc/argv — Argument count and string array of command-line args.

Syntax reference

Syntax reference:

int main(void) { return 0; }

Informative example

Example program:

#include <stdio.h>

int main(int argc, char *argv[]) {
    printf("argc=%d program=%s\n", argc, argv[0]);
    return 0;
}

Execution workflow

Best practices

• Enable warnings: gcc -Wall -Wextra -std=c11 source.c -o app
• Give every variable a defined value before it is read.
• Stay inside array bounds — C will not stop you from over-running a buffer.

Common mistakes

• Reading uninitialized storage — behavior is undefined.
• Dismissing compiler warnings instead of fixing root causes.
• Ignoring NULL returns from malloc, fopen, and similar APIs.

Hands-on exercise

Practice problems:

• Print all command-line arguments
• Return different exit codes

Summary

Main Function in C — Program entry — signatures, argc/argv, exit codes.