Exercise 0: Hello World

Programming Workshop in C/C++ (67315) -- C Exercise 0

Topics: Introduction to C, Compilation, main Function, Standard I/O.

1. Overview

This is the introductory exercise for the course. The goal is to verify that your development environment is set up correctly and that you can write, compile, and run a basic C program.

You will write a simple program that prints output to the console using printf.

2. Key Concepts

2.1 The main Function

Every C program begins execution from the main function. It must return an integer -- by convention, 0 (or EXIT_SUCCESS) indicates successful execution:

int main() {
    // your code here
    return 0;
}

2.2 Including Headers

To use standard I/O functions like printf, you must include the appropriate header:

#include <stdio.h>

2.3 Printing Output with printf

The printf function prints formatted output to the console. It uses format specifiers to control how values are displayed:

Example:

printf("Hello, World!\n");
printf("%d\n", 42);
printf("%ld\n", (long) 1 / 10);

2.4 Compilation

Compile your program using gcc:

gcc -Wall -Wextra -Wvla -std=c99 hello_world.c -o hello_world

Flags explained:

• -Wall -- enable most common warnings
• -Wextra -- enable additional warnings
• -Wvla -- warn about variable-length arrays
• -std=c99 -- use the C99 standard

Then run the compiled program:

./hello_world

3. File Structure

hello_world.c

A single source file containing the main function:

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

4. What to Pay Attention To

• Make sure to return 0 from main -- this signals successful execution to the operating system
• Always include <stdio.h> when using printf
• Compile with all warning flags enabled -- fix any warnings before submitting
• The \n at the end of printf output ensures a newline after your text