Stopwatch using C language

Create a digital stopwatch program in C which runs on linux base system. keyboardhit() function simply stands for keyboard hit. After pressing a key it generates a signal and returns a non zero integer. In this, there are 4 loops, 1st loop for hours, 2nd for minutes, 3rd for seconds and 4th loop for maintaining the speed of seconds(3 loop). After running this program it wait for a keyboard start(s) key to be pressed and when key is pressed, it generates a signal. For storing a keyboard key there is a variable(c), if c is equal to p key then it calls the wait function. The thread is running in the background and we are waiting for the start key to be pressed. After pressing s key, the thread again jumps to thread_join function, if r key is pressed, then it jumps into reset label and all the loops are again starts with zeros, if s key is pressed it jumps into start label and if e key is pressed it calls the exit() function and program gets terminated. Prerequisite : Threads in c, Wait system call

To execute the program we use following command :

Input:
Press a key :
s -> start
e -> exit
r -> reset
p -> pause

Output :

C

// C code to create stop watch

// Header file for necessary system library
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <unistd.h>

// starting from zero
#define MIN 0

// 1 hr= 60 min ; 1 min= 60 sec
#define MAX 60

#define MILLI 200000

int i, j, k, n, s;
char c;
pthread_t t1;

// Function to perform operations
// according keyboard hit.
int keyboardhit(void)
{
    struct termios oldt, newt;
    int ch;
    int oldf;

    tcgetattr(STDIN_FILENO, &oldt);
    newt = oldt;
    newt.c_lflag &= ~(ICANON | ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &newt);
    oldf = fcntl(STDIN_FILENO, F_GETFL, 0);
    fcntl(STDIN_FILENO, F_SETFL, oldf | O_NONBLOCK);

    ch = getchar();

    tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
    fcntl(STDIN_FILENO, F_SETFL, oldf);

    if (ch != EOF) {
        ungetc(ch, stdin);
        return 1;
    }

    return 0;
}

// display stopwatch on screen
void print()
{
    // clear screen escape sequence
    printf("&#092;&#048;33[2J&#092;&#048;33[1;1H");

    // Display Hour Min Sec in screen
    printf("TIME\t\t\t\tHr: %d Min: %d Sec: %d", n, i, j);
}

// function to pause stopwatch
void* wait(void* arg)
{

    while (1) {

        // wait for keyboard signal if keyboard
        // hit it return non integer number
        if (keyboardhit()) {
            // take input from user and do
            // operation accordingly
            c = getchar();
            if (c == 'S' || c == 's') {
                break;
            }
            else if (c == 'r' || c == 'R') {
                s = 1;
                break;
            }
            else if (c == 'e' || c == 'E')

                exit(0);
        }
    }
}

// driver code
int main()
{

    // label to reset the value
reset:
    n = MIN;
    i = MIN;
    j = MIN;
    k = MIN, s = MIN;

    print();

    while (1) {

        /* s for start
        e for exit
        p for pause
        r for reset
        */
        if (keyboardhit()) {
            c = getchar();

            if (c != 's')
                continue;

            for (n = MIN; n < MAX; n++) {
                for (i = MIN; i < MAX; i++) {
                    for (j = MIN; j < MAX; j++) {
                        for (k = MIN; k < MILLI; k++) {
                        start:
                            print();
                            if (keyboardhit()) {
                                c = getchar();

                                if (c == 'r' || c == 'R')
                                    goto reset;
                                else if (c == 'e' || c == 'E')
                                    exit(0);
                                else if (c == 's' || c == 'S')
                                    goto start;
                                else if (c == 'P' || c == 'p') {

                                    pthread_create(&t1, NULL, &wait, NULL);

                                    // waiting for join a thread
                                    pthread_join(t1, NULL);
                                    if (s == 1)
                                        goto reset;
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    return 0;
}

Output: