C Exercises: Generates 50 random numbers between -0.5 and 0.5

C Basic Declarations and Expressions: Exercise-66 with Solution

Write a C program that generates 50 random numbers between -0.5 and 0.5 and writes them to the file rand.dat. The first line of ran.dat contains the number of random numbers, while the next 50 lines contain 50 random numbers.

Sample Solution:

C Code:

#include <stdio.h> 
#include <stdlib.h> 
#include <time.h> 
#define N 50
int main() {
  int i;
  char str;
  FILE * fptr;
  
  // Open a file for writing
  fptr = fopen("rand.dat", "w");
  if (fptr == NULL) {
    printf("Error in creating output.dat\n");
    return 0;
  }

  // Seed the random number generator
  srand(time(NULL));
  
  // Write the number of values to the file
  fprintf(fptr, "%d\n", N);
  
  // Generate and write random numbers to the file
  for (i = 1; i <= N; i++) {
    fprintf(fptr, "%0.4lf\n", (rand() % 2001 - 1000) / 2.e3);
  }
  
  // Close the file
  fclose(fptr);
  
  // Open the file for reading
  fptr = fopen ("rand.dat", "r");  
  str = fgetc(fptr);
  
  // Print the contents of the file
  while (str != EOF)
  {
    printf ("%c", str);
    str = fgetc(fptr);
  }
  
  // Close the file
  fclose(fptr);
  
  return 0;
}

Sample Output:

50
-0.4215
0.2620
0.3065
-0.0485
-0.2085
-0.2490
-0.2780
0.2905
-0.3120
0.1275
0.4010
0.3060
0.4680
-0.1135
0.0130
-0.0145
-0.1890
-0.3825
0.3790
-0.2370
0.0840
-0.1985
0.2065
0.4445
0.0785
-0.2370
-0.0705
0.3870
-0.4695
0.1525
0.2755
0.3880
-0.3075
-0.1400
-0.3825
-0.0155
-0.1105
-0.1605
-0.4470
0.0780
0.4675
0.2330
-0.3380
0.2135
0.3980
0.1750
0.4780
-0.2915
0.0715
0.3565

Flowchart:

C programming Code Editor:

Previous:Write a C program that accepts integers from the user until a zero or a negative number, display the number of positive values, the minimum value, the maximum value and the average of all numbers
Next: Write a C program to evaluate the equation y=xn when n is a non-negative integer.