floting point divide by 0 error

[rajat.sethi93]

#include<stdio.h>
#include<conio.h>
void main()
{
 float a[5][5],x[3];float t,s;
 int i,j,k;
 printf("enter a matrix of order 3*4");
 for(i=0;i<3;i++)
 {
  for(j=0;j<4;j++)
  {
  scanf("%f",&a[i][j]);
  }
 }
 for(i=0;i<3;i++)
 {
  for(j=0;j<4;j++)
  printf("%f ",a[i][j]);
  printf("\n");
 }
 for(i=0;i<=1;i++)
 {
  for(j=i+1;j<=2;j++)
  {
  t=a[j][i]/a[i][i];
  for(k=i;k<=3;k++)
  a[j][k]=a[j][k]-t*a[i][k];
  }
 }
 printf("The upper triangular matrix is as\n");
 for(i=0;i<3;i++)
 {
 for(j=0;j<4;j++)
 printf(" %f",a[i][j]);
 printf("\n");
 }
 for(i=2;i>=0;i--)
 {
  s=0.0;
  for(j=i+1;j<3;j++)
  {
   s=s+a[i][j]*x[j];
   x[i]=(a[i][3]-s)/a[i][i];
  }
 }
 printf("\nRoots of the equation are");
 for(i=0;i<=2;i++)
 printf(" %f",x[i]);
 getch();
}

[rajat.sethi93]

Can any one help me with this??????????????

[WaltP]

Where are you dividing?

Just before those statements, output the values used to figure out the denominator. For example, for line 43, display i and a[i][i]
Now figure out what that value should be and why it is zero.

[rajat.sethi93]

can u get the errors out of it..............

[rajat.sethi93]

its basically Guass elimination method

[NathanOliver]

We wouldnt know where to start. Did you try printing out the values before you divide to see where you are dividing by 0 like WlatP suggested? Learning how to debug your code is an important part of becoming a programer.

[DavidB]

Like WaltP already suggested, go through your code and find all the places where division occurs. I see it on lines 25 and 43. Insert a line or two before the division statements that check to see if the denominator is 0:
e.g. - if (a[i][i] == 0) printf("\nAttempted division by zero. Execution aborted.");return 0;

Or something like that. That way your program doesn't just crash.

In any case, you are not going to be able to solve this equation completely. To solve for N variables, you need N equations. You have a 3X4 matrix (I think), so you will not be able to solve uniquely for all the variables. Is your system 3X4? The a matrix is 5X5, the x vector is 3, and your comment for the data entry indicates a 3X4 system. Which is it?

[rajat.sethi93]

thanks