Why does my program crash when I introduce arithmetic operations involving arrays? - c

Question

The purpose of the program I'm developing is to get data from two different files, perform mathematical operations involving these data, and then store the results in another file. The number of lines is counted in order to perform further calculations such as averages etc. Everything is working fine when no arithmetical operations are include. For instance, the following program successfully opens the files, reads them, allocates memory for the data, stores them into these arrays, prints the arrays contents in order to verify if the data are there, and then writes the data to another file:
#include <stdio.h>
#include <stdlib.h>
int main()
{
float *VarA;
float *VarB;
int n = 0;
int m = 0;
int i;
FILE *input1;
FILE *input2;
FILE *output;
input1 = fopen("C:\\...\\test.txt","r");
if (input1 == NULL)
{
printf("Error! Could not open input 1.\n");
exit(1);
}
else
printf("Input1 opening: OK.\n");
input2 = fopen("C:\\...\\test2.txt","r");
if (input2 == NULL)
{
printf("Error! Could not open input 2.\n");
exit(1);
}
else
printf("Input2 opening: OK.\n");
while(fscanf(input1,"%f") == 1)
n++;
rewind(input1);
printf("n = %i\n", n);
while(fscanf(input2,"%f") == 1)
m++;
rewind(input2);
printf("m = %i\n", m);
if(m != n)
{
printf("Error: Number of rows does not match!\n");
exit(1);
}
else
printf("Number of rows matches.\n");
VarA = calloc(n, sizeof(float));
if(VarA == NULL)
{
printf("Could not allocate memory for VarA.\n");
exit(1);
}
VarB = calloc(m, sizeof(float));
if(VarA == NULL)
{
printf("Could not allocate memory for VarB.\n");
exit(1);
}
for(i = 0; i < n; i++)
fscanf(input1,"%f",&VarA[i]);
fclose(input1);
for(i = 0; i < m; i++)
fscanf(input2,"%f",&VarB[i]);
fclose(input2);
for(i = 0; i < n; i++)
{
printf("VarA: %f\n",VarA[i]);
printf("VarB: %f\n",VarB[i]);
}
output = fopen("C:\\...\\out.txt","w");
if (output == NULL)
{
printf("Error! Could not open output.\n");
exit(1);
}
else
printf("Output opening: OK.\n");
for(i = 0; i < n; i++)
{
fprintf(output,"VarA: %f\n",VarA[i]);
fprintf(output,"VarB: %f\n",VarB[i]);
}
fclose(output);
free(VarA);
free(VarB);
return 0;
}
But if I add any simple arithmetic operation involving these arrays, the program simply crashes right after the second input is opened. For instance, suppose that I add the following lines to the code:
float SumA;
SumA = VarA[0] + VarB[0];
printf("SumA is: %f\n", SumA);
So that we get:
#include <stdio.h>
#include <stdlib.h>
int main()
{
float *VarA;
float *VarB;
float SumA;
int n = 0;
int m = 0;
int i;
FILE *input1;
FILE *input2;
FILE *output;
input1 = fopen("C:\\...\\test.txt","r");
if (input1 == NULL)
{
printf("Error! Could not open input 1.\n");
exit(1);
}
else
printf("Input1 opening: OK.\n");
input2 = fopen("C:\\...\\test2.txt","r");
if (input2 == NULL)
{
printf("Error! Could not open input 2.\n");
exit(1);
}
else
printf("Input2 opening: OK.\n");
while(fscanf(input1,"%f") == 1)
n++;
rewind(input1);
printf("n = %i\n", n);
while(fscanf(input2,"%f") == 1)
m++;
rewind(input2);
printf("m = %i\n", m);
if(m != n)
{
printf("Error: Number of rows does not match!\n");
exit(1);
}
else
printf("Number of rows matches.\n");
VarA = calloc(n, sizeof(float));
if(VarA == NULL)
{
printf("Could not allocate memory for VarA.\n");
exit(1);
}
VarB = calloc(m, sizeof(float));
if(VarA == NULL)
{
printf("Could not allocate memory for VarB.\n");
exit(1);
}
for(i = 0; i < n; i++)
fscanf(input1,"%f",&VarA[i]);
fclose(input1);
for(i = 0; i < m; i++)
fscanf(input2,"%f",&VarB[i]);
fclose(input2);
for(i = 0; i < n; i++)
{
printf("VarA: %f\n",VarA[i]);
printf("VarB: %f\n",VarB[i]);
}
output = fopen("C:\\...\\out.txt","w");
if (output == NULL)
{
printf("Error! Could not open output.\n");
exit(1);
}
else
printf("Output opening: OK.\n");
for(i = 0; i < n; i++)
{
fprintf(output,"VarA: %f\n",VarA[i]);
fprintf(output,"VarB: %f\n",VarB[i]);
}
fclose(output);
SumA = VarA[0] + VarB[0];
printf("SumA is: %f\n", SumA);
free(VarA);
free(VarB);
return 0;
}
Then the program stops working. I tried to change the positions of these lines, but the result is the same. Does anyone know what I'm doing wrong?