C program to print digital clock with current time

The time.h header defines four variable types, two macro and various functions for manipulating date and time. A brief description of the variable types defined in the header time.h is as : 

• size_t : This is the unsigned integral type and is the result of the sizeof keyword.
• clock_t : This is a type suitable for storing the processor time.
• time_t is : This is a type suitable for storing the calendar time.
• struct tm : This is a structure used to hold the time and date.

Below is the implementation of digital clock. On executing the program, the output window will show the time when the program was executed. 

C

// C implementation of digital clock
#include <stdio.h>
#include <time.h>

// driver code
int main()
{
    time_t s, val = 1;
    struct tm* current_time;

    // time in seconds
    s = time(NULL);

    // to get current time
    current_time = localtime(&s);

    // print time in minutes,
    // hours and seconds
    printf("%02d:%02d:%02d",
           current_time->tm_hour,
           current_time->tm_min,
           current_time->tm_sec);

    return 0;
}

Output : 

Below is the C program to show the current time inside a rectangular bar. The output window shows the day, month, date, current time and year.

C

// C program to print digital
// clock using graphics
#include <graphics.h>
#include <time.h>

// driver code
int main()
{
    // DETECT is a macro defined in
    // "graphics.h" header file
    int dt = DETECT, gmode, midx, midy;
    long current_time;
    char strftime[30];

    // initialize graphic mode
    initgraph(&dt, &gmode, "");

    // to find mid value in horizontal
    // and vertical axis
    midx = getmaxx() / 2;
    midy = getmaxy() / 2;

    // set current colour to white
    setcolor(WHITE);

    // make a rectangular box in
    // the middle of screen
    rectangle(midx - 200, midy - 40, midx + 200,
                                     midy + 40);

    // fill rectangle with white color
    floodfill(midx, midy, WHITE);
    while (!kbhit()) {

        // get current time in seconds
        current_time = time(NULL);

        // store time in string
        strcpy(strftime, ctime(&current_time));

        // set color of text to red
        setcolor(RED);

        // set the text justification
        settextjustify(CENTER_TEXT, CENTER_TEXT);

        // to set styling to text
        settextstyle(SANS_SERIF_FONT, HORIZ_DIR, 3);

        // locate position to write
        moveto(midx, midy);

        // print current time
        outtext(strftime);
    }
    getch();

    // deallocate memory for graph
    closegraph();
}

Output : 

References : 
cprogramforbeginners