Introduction:

In this program, we will create a simple countdown timer that counts down from a user-specified number of seconds. The program will display the current time remaining on the screen every second. This is a basic example that introduces concepts like loops, time delay functions, and user input handling in C programming.

Objective:

The goal is to implement a countdown timer that begins from a specified number of seconds, decrementing every second, and finally prints a message when the countdown reaches zero.

Code:

#include 
#include 
#include   // for sleep() function

int main() {
    int seconds;

    // Ask the user for the number of seconds to countdown from
    printf("Enter the number of seconds to countdown from: ");
    scanf("%d", &seconds);

    // Validate if the number of seconds is positive
    if (seconds <= 0) { printf("Please enter a valid positive number.\n"); return 1; } // Countdown loop while (seconds > 0) {
        printf("%d seconds remaining...\n", seconds);
        sleep(1);  // Wait for 1 second
        seconds--;  // Decrease the countdown
    }

    // Countdown finished
    printf("Time's up!\n");
    return 0;
}

Explanation of the Program Structure:

The program begins by prompting the user to input a number of seconds to start the countdown. It then enters a while loop, where it repeatedly prints the remaining time every second using the sleep(1) function to create a delay of one second between each iteration. The loop continues until the countdown reaches zero, at which point a “Time’s up!” message is displayed.

How to Run the Program:

1. Open a text editor and paste the C code provided above.
2. Save the file with a .c extension (e.g., countdown_timer.c).
3. Open a terminal or command prompt on your computer.
4. Navigate to the directory where the C file is saved.
5. Compile the program using a C compiler. For example, using gcc countdown_timer.c -o countdown_timer on a Linux or macOS terminal.
6. Run the compiled program by typing ./countdown_timer in the terminal (for Linux/macOS) or countdown_timer.exe (for Windows).
7. Input the number of seconds when prompted, and the countdown will begin.