/****
This program generates a series of random numbers and saves them in a
file.  It uses C's capabilities for random number generation. The user
is first prompted for a seed for the random number generator. The
numbers are then generated (the quantity of numbers is determined by
the constant MaxNum) in the function GenRand.  The data are then saved
in the function SaveRand, which first prompts the user for a file
name. After the name is given the file is opened -- if this causes an
error the calling program is notified. If there was no error the data
are saved and the file is closed. A NO_ERROR condition is returned to
the calling program.  Written by Erik Cheever, 1/94
****/

#include <stdio.h>
#include <stdlib.h>       // This library contains random number stuff

#define MaxNum 100        // Number of random numbers generated
#define ERROR -1          // Constants used to signify errors
#define NO_ERROR 0        

// Generate the random numbers and save in array
void GenRand(int *Nums) {
    int i, randNum;

    for (i=0; i<MaxNum; i++) {
        randNum = rand();     // This is a (bad) library routine to generate a random number */
        Nums[i] = randNum;    // Save in array
    }
}

// Saves random numbers, returns NO_ERROR if no errors
int SaveRand(int *Nums) { 
    int i;
    char FileName[80];
    FILE *OutFile;

    printf("Enter file name: ");              // Get name of file
    scanf("%s",FileName);
    OutFile = fopen(FileName,"w");            // Open the file
    if (OutFile == NULL) {                    // If error, return and report
        return (ERROR);
    }
    
    fprintf(OutFile,"%d\n",MaxNum);           // First line in file is number of numbers
    for (i=0; i<MaxNum; i++) {                // Write the numbers to the file
        fprintf(OutFile,"%d\n",Nums[i]);
    }
    fclose(OutFile);                          // Close the file

    return(NO_ERROR);                         // Return, report no errors
}

main() {
    int randNums[MaxNum], i, iseed;

    // user interaction stuff
    printf("This program generates a series of random values and then saves it.\n");
    printf("Enter the seed for the random number generator:");
    scanf("%d",&iseed);

    // sets the seed value for the random number generator
    srand(iseed);

    GenRand(randNums); /*Note we use pointer to array since we want values changed*/
    if (SaveRand(randNums) == NO_ERROR) {
        printf("\nDone.\n");
    }
    else {
        printf("Error in SaveRand.\n");
    }
}