Using pointers

Code:

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#include <stdio.h>
#include <stdlib.h>

void find_closest_flight(int desired_time, int *departure_time, int *arrival_time);




int main()
{
    int hour = 0;
    int minute = 0;

    // Departure times in minutes after midnight
    // int departure_times[] =
    // {8*60, 9*60+43, 11*60+19, 12*60+47,
    // 14*60, 15*60+45, 19*60, 21*60+45};

    // Arrival times in minutes after midnight
    // int arrival_times[] =
    // { 10*60+16, 11*60+52, 13*60+31, 15*60,
    // 16*60+8, 17*60+55, 21*60+20, 23*60+58};

    // Length of the array.
    //int length = sizeof(arrival_times) / sizeof(arrival_times[0]);

    int departure_hour, departure_min;
    char departure_halfday;
    int arrival_hour, arrival_min;
    char arrival_halfday;

    // int i;
    // int time_in_minutes;
    // int difference1, difference2, difference3;
    // int min_difference, best_index;

    printf ("\nEnter a 24-hour time: ");
    scanf("%d:%d", &hour, &minute);
    printf ("You entered %2d:%02d\n", hour, minute);

    // Get user's time in minutes after midnight.
    //time_in_minutes = hour*60 + minute;

    //Look through the departure time array and find the value that
    //is closest to the time entered by the user.
    //min_difference = 100000;
    // for (i = 0; i < length; i++)
    // {
        //Difference between user's time and flight time today.
        // difference1 = abs(time_in_minutes - departure_times[i]);
        // if (difference1 < min_difference)
        // {
            // min_difference = difference1;
            // best_index = i;
        // }

      // Difference between user's time and flight time previous day.
        // difference2 = abs(time_in_minutes - (departure_times[i]  - 60*24));
        // if (difference2 < min_difference)
        // {
            // min_difference = difference2;
            // best_index = i;
        // }

        //Difference between user's time and flight time next day.
        // difference3 = abs(time_in_minutes - (departure_times[i] + 60*24));
        // if (difference3 < min_difference)
        // {
            // min_difference = difference3;
            // best_index = i;
        // }
    // }

    // We have determined the closes departure time in minutes after midnight.
    // Now output it as a time of day.
    // i = best_index;
    // departure_hour = departure_times[i] / 60;
    // departure_min = departure_times[i] % 60;
    // departure_halfday = 'a';
    // arrival_hour = arrival_times[i] / 60;
    // arrival_min = arrival_times[i] % 60;
    // arrival_halfday = 'a';

    if (departure_hour >= 12)
    {
        // Departure is at noon or later.
        departure_halfday = 'p';
        if (departure_hour > 12)
        {
            departure_hour -= 12;
        }
    }
    else
    {
      // Departure is before noon.
      if (departure_hour < 1)
        {
            // 30 minutes after midnight should be 12:30 A.M.
            departure_hour += 12;
        }
    }

    if (arrival_hour >= 12)
    {
        // Arrival time is at noon or later.
        arrival_halfday = 'p';
        if (arrival_hour > 12)
        {
            arrival_hour -= 12;
        }
    }
    else
    {
      // Arrival time is before noon.
      if (arrival_hour < 1)
        {
            arrival_hour += 12;
        }
    }

    printf ("closest departure time is %2d:%02d %c.m., ",
        departure_hour, departure_min, departure_halfday);

    printf("arriving at %2d:%02d %c.m.",
        arrival_hour,  arrival_min,  arrival_halfday);
    getchar();
    getchar();
    return 0;
}


void find_closest_flight(int desired_time, int *departure_time, int *arrival_time)
{
        int hour = 0;
        int minute = 0;
        //int desired_time;
        //int departure_time;
        //int arrival_time;
       
        departure_time = &departure_time;
        arrival_time = &arrival_time;
       
        int departure_hour, departure_min;
    char departure_halfday;
    int arrival_hour, arrival_min;
    char arrival_halfday;
       
       
    int i;
    int time_in_minutes;
    int difference1, difference2, difference3;
    int min_difference, best_index;
       
        // Departure times in minutes after midnight
    int departure_times[] =
    {8*60, 9*60+43, 11*60+19, 12*60+47,
    14*60, 15*60+45, 19*60, 21*60+45};

    // Arrival times in minutes after midnight
    int arrival_times[] =
    { 10*60+16, 11*60+52, 13*60+31, 15*60,
    16*60+8, 17*60+55, 21*60+20, 23*60+58};
       
        i = best_index;
    departure_hour = departure_times[i] / 60;
    departure_min = departure_times[i] % 60;
    departure_halfday = 'a';
    arrival_hour = arrival_times[i] / 60;
    arrival_min = arrival_times[i] % 60;
    arrival_halfday = 'a';
        int length = sizeof(arrival_times) / sizeof(arrival_times[0]);
               
    // Get user's time in minutes after midnight.
    time_in_minutes = hour*60 + minute;       
       
        //Look through the departure time array and find the value that
    //is closest to the time entered by the user.
    min_difference = 100000;
    for (i = 0; i < length; i++)
    {
        // Difference between user's time and flight time today.
        difference1 = abs(time_in_minutes - departure_times[i]);
        if (difference1 < min_difference)
        {
            min_difference = difference1;
            best_index = i;
        }

        // Difference between user's time and flight time previous day.
        difference2 = abs(time_in_minutes - (departure_times[i]  - 60*24));
        if (difference2 < min_difference)
        {
            min_difference = difference2;
            best_index = i;
        }

        // Difference between user's time and flight time next day.
        difference3 = abs(time_in_minutes - (departure_times[i] + 60*24));
        if (difference3 < min_difference)
        {
            min_difference = difference3;
            best_index = i;
        }
   
return;
                }

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Does anyone know how to write pointers in the (void) Function. Also how store time inside the pointers.

What do you mean by "write pointers in the function"? If intptr is a pointer-to-int, you can store an int at the address pointed to by writing *intptr = 43.

I mean declaring and calling a pointer under the void find_closest_flight(int desired_time, int *departure_time, int *arrival_time) seen in my example.

You declare a pointer the same as any other variable: type first, then name. You cannot call a pointer, just as you cannot call any other variable. Edit: And this

Code:

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        departure_time = &departure_time;
        arrival_time = &arrival_time;

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is a really bad idea.