/*
 * Program RPM.c
 *
 * Illustrates how a single function can pass back several values using
 * parameters passed by reference.
 *
 * Displays the minimum, maximum and average values of an electric motor
 * RPM data stored in integer array.
 */

#include <stdio.h>

/* Number of RPM entries in the array */
#define DATASIZE 16

/* Function prototypes */
void RPMstats(int * min, int * max, double * avg, int data[]);

int main(void)
{

    /* Declare int variables to hold minimum, and maximum RPM values */
	int min=0,max=0;
    /* declare double variable to store the average RPM value */
	double avg=0.00;

    /* Hard-coded RPM data values (in real life would be provided by sensor. */
    int RPMdata[] = { 2023, 1987, 1902, 1902, 1689, 1778, 1939, 1546,
                      1345, 1777, 2321, 2322, 2331, 2200, 2222, 1954};

    /* Call RPMstats function to obtain minimum, maximum and average RPM values */
	RPMstats(&min,&max,&avg,RPMdata);

    /* Print the results */
    printf("The min value: %d\n", min);
	printf("The maximum value: %d\n", max);
	printf("The average value: %lf\n", avg);

    /* Pause */
    printf("Press ENTER to exit");
    getchar();

    /* Return success to OS */
    return 0;
}

/* Function RPMstats
 *
 * Returns minimum, maximum and average RPM values to the calling program
 * using parameters passed by reference.
 *
 * Parameter min:  pointer to integer, will hold the value of the minimum RPM
 * Parameter max:  pointer to integer, will hold the value of the maximum RPM
 * Parameter avg:  pointer to double,  will hold the value of the average RPM
 * Parameter data: array containing the RPM values
 *
 * Return: no return value. All results passed back to parameters by reference
 */
void RPMstats(int * min, int * max, double * avg, int data[])
{
    /* local variables */
     int a=0;
	 double sum=0.00;

    /* initialise min, max and sum to the value of the 1st element in array */
	*min=data[a];
	*max=data[a];

    /* obtain min, max, and the sum in loop through rest of array*/
    for(a=0;a<DATASIZE;a++)
	{
		if(data[a]<=*min)
		*min=data[a];
		else
		*min=*min;

		if(data[a]>=*max)
		*max=data[a];
		else
		*max=*max;

		sum+=data[a];

	}

    /* Pass back value of average */
	*avg=sum/DATASIZE;
}