# Gauss Elimination Method Using C

Earlier in Gauss Elimination Method Algorithm and Gauss Elimination Method Pseudocode , we discussed about an algorithm and pseudocode for solving systems of linear equation using Gauss Elimination Method. In this tutorial we are going to implement this method using C programming language.

## Complete Program for Gauss Elimination method using C Programming Language

``````
#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<stdlib.h>

#define   SIZE   10

int main()
{
float a[SIZE][SIZE], x[SIZE], ratio;
int i,j,k,n;

clrscr();

/* Inputs */
/* 1. Reading number of unknowns */
printf("Enter number of unknowns: ");
scanf("%d", &n);
/* 2. Reading Augmented Matrix */
for(i=1;i<=n;i++)
{
for(j=1;j<=n+1;j++)
{
printf("a[%d][%d] = ",i,j);
scanf("%f", &a[i][j]);
}
}
/* Applying Gauss Elimination */
for(i=1;i<=n-1;i++)
{
if(a[i][i] == 0.0)
{
printf("Mathematical Error!");
exit(0);
}
for(j=i+1;j<=n;j++)
{
ratio = a[j][i]/a[i][i];

for(k=1;k<=n+1;k++)
{
a[j][k] = a[j][k] - ratio*a[i][k];
}
}
}
/* Obtaining Solution by Back Subsitution */
x[n] = a[n][n+1]/a[n][n];

for(i=n-1;i>=1;i--)
{
x[i] = a[i][n+1];
for(j=i+1;j<=n;j++)
{
x[i] = x[i] - a[i][j]*x[j];
}
x[i] = x[i]/a[i][i];
}
/* Displaying Solution */
printf("\nSolution:\n");
for(i=1;i<=n;i++)
{
printf("x[%d] = %0.3f\n",i, x[i]);
}
getch();
return(0);
}
``````

## Output: Gauss Elimination Method for Solving Systems of Linear Equations

```Enter number of unknowns: 3
a[1][1] = 1
a[1][2] = 1
a[1][3] = 1
a[1][4] = 9
a[2][1] = 2
a[2][2] = -3
a[2][3] = 4
a[2][4] = 13
a[3][1] = 3
a[3][2] = 4
a[3][3] = 5
a[3][4] = 40

Solution:
x[1] = 1.000
x[2] = 3.000
x[3] = 5.000
```
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