C Programming Language Standard

In this article, we will learn about the standards defined in the C programming language. These standards specify how programs should be compiled and executed as defined by the development community.

To understand this concept, let's examine a common C program that demonstrates standard compliance issues −

What is the C Programming Language Standard?

The C programming language standard defines the official specification for how C compilers should behave. It establishes the correct syntax, semantics, and behavior of C programs. The latest C standard is ISO/IEC 9899:2018, also known as C18, which was released in June 2018.

This standard defines crucial aspects such as −

• How programs should be compiled and executed
• Correct function declarations and definitions
• Behavior of built-in functions and operators
• Memory management rules

Syntax

The standard defines two correct ways to declare the main() function −

// No parameters
int main(void) {
    /* program code */
    return 0;
}

// With command-line arguments
int main(int argc, char *argv[]) {
    /* program code */
    return 0;
}

Example: Standard vs Non-Standard main() Function

Here's an example demonstrating the difference between standard and non-standard main() declarations −

#include <stdio.h>

/* Standard-compliant main() function */
int main(void) {
    printf("This is a standard-compliant C program<br>");
    printf("main() returns int and has proper return statement<br>");
    return 0;  /* Required by C standard */
}

This is a standard-compliant C program
main() returns int and has proper return statement

Non-Standard Example (Avoid This)

The following code violates C standards −

#include <stdio.h>

/* Non-standard: void main() is not compliant */
void main() {
    printf("This violates C standard<br>");
    /* Missing return statement */
}

Note: Some compilers like Turbo C accept void main(), but this is non-standard and should be avoided for portable code.

Key Points

• Always use int main() instead of void main()
• Include return 0; to indicate successful program termination
• Follow standard syntax for better portability across different compilers
• Standard-compliant code ensures consistent behavior across platforms

Conclusion

Following C programming standards ensures your code is portable, reliable, and behaves consistently across different compilers and platforms. Always use int main() with proper return statements for standard-compliant programs.