C program for inverse of a matrix

/*Inverse of a matrix*/

#include<stdio.h>

#include<math.h>

void

main()

{

                int i,j,det,k,a[20][20];

                float I[20][20],U[20][20];

                printf("enter the elements of input matrix:");

                for(i=0;i<2;i++)

                {

                                for(j=0;j<2;j++)

                                                scanf("%d",&a[i][j]);

                }

                printf("the input matrix is:");

                printf("\n");

                for(i=0;i<2;i++)

                {

                                for(j=0;j<2;j++)

                                                printf("%d\t",a[i][j]);

                                printf("\n");

                }

                /*matrix determinant*/

                det=(a[0][0]*a[1][1])-(a[0][1]*a[1][0]);

                printf("\n The determinant is=%d\n",det);

                /*matrix inverse*/

                if(det==0)

                                printf("The matrix inverse is not possible:");

                else

                {

                                for(i=0;i<2;i++)

                                {

                                                for(j=0;j<2;j++)

                                                {

                                                                if(i==j)

                                                                {

                                                                                I[i][j]=(a[(i+1)%2][(j+1)%2]);

                                                                }

                                                                else

                                                                {

                                                                                I[i][j]=-(a[i][j]);

                                                                }

                                                }

                                }

                                printf("The inverse matrix is \n");

                                for(i=0;i<2;i++)

                                {

                                                for(j=0;j<2;j++)

                                                                printf("%.4f\t",(I[i][j]/det));

                                                printf("\n");

                                }

                                /*product matrix*/

                                for(i=0;i<2;i++)

                                {for(j=0;j<2;j++)

                               

                                {

                                                U[i][j]=0;

                                                for(k=0;k<2;k++)

                                                                U[i][j]=U[i][j]+a[i][k]*I[k][j];

                                }

                                }

                                printf("\n the product matrix is:\n");

                                for(i=0;i<2;i++)

                                {

                                                for(j=0;j<2;j++)

                                                                printf("%.4f\t",(U[i][j]/det));

                                                printf("\n");

                                }

                }

}

RESULT 1:

enter the elements of input matrix:1 2 3 4

the input matrix is:

1       2

3       4

 The determinant is=-2

The inverse matrix is

-2.0000 1.0000

1.5000  -0.5000

 the product matrix is:

1.0000  0.0000

0.0000  1.0000

Press any key to continue

RESULT 2:

enter the elements of input matrix:1 1 1 1

the input matrix is:

1       1

1       1

 The determinant is=0

The matrix inverse is not possible:

Press any key to continue