error while Using malloc in creating 2D and 1D array

Question

I am creating 1d arrays B and T of n size and a 2D array A of nxn size,where n has been computed earlier. But the program crashes after Pause, what am i possibly doing wrong??

float *B = malloc(sizeof(int) * (n));
float *T = malloc(sizeof(int) * (n));
system("PAUSE");
float **A;                                                    
A = malloc(sizeof(int) * (n));
for(j = 0; j < n; j++)
{ 
    A[j] = malloc(sizeof(int) * (j));
}

i, j and n are integers.

Answer 1

a 2D array A of nxn size

You're passing the wrong types to sizeof . You should be using sizeof(float) and sizeof(float *) . But the more serious (and insidious) problem is:

A[j]=(float*)malloc(sizeof(int)*(j));
                                 ^

You want n instead of j .

Answer 2

Never repeat the type name in the argument to malloc() ; doing so makes it easy to say the wrong type, which creates errors.

You should use sizeof , like so:

float *B = malloc(n * sizeof *B);
float **A = malloc(n * sizeof *A);
for(j = 0; j < n; ++j)
  A[j] = malloc(n * sizeof *A[j]);

Also, in C you shouldn't cast the return value of malloc() .