[help]segmentation fault

[hakagiri]

i've problem with my source code

#include<stdio.h>

main()
{
	int j;
	float t[100],dt,dx,*r;

	dt=0.01;
	dx=0.1;	
	t[0]=0;
	
	{
		t[j]=t[j-1]+dt;
		*r=t[j]/(dx*dx);
		printf("t[%d] =%.2f\n",j,t[j]);
		printf("\n\nr[%d] =%.2f\n",j,*r);
		j++;
	}
	while(*r<=0.5);
}

[gerard4143]

You didn't allocate or assign any memory to r...

[Cabhan]

The segfault is probably occurring because you didn't malloc r, like gerard said. However, you have other problems too.

First, you don't initialize j. j will probably default to 0, but you should assign 0 to it initially.

Also, I assume you're trying to use a do-while loop? You forgot the "do".

[Rubberman]

The pointer variable is not pointing to any valid memory (float) address. This is why you are crashing. Better declaration:

    float t[100],dt,dx,*r = (float*)malloc(sizeof(float));

P.S. If this is a school exercise, please observe that the forums do not allow help with such - see the terms of use for details of what is allowed.