To find the given matrix is a unit matrix or not Using C

# include <stdio.h>
# include <conio.h>

void main()
{
int mat[10][10] ;
int i, j, size, flag = 1 ;
clrscr() ;
printf("Enter size of the square matrix : ") ;
scanf("%d", &size) ;
printf("\nEnter the elements of the matrix : \n\n") ;
for(i = 0 ; i < size ; i++)
for(j = 0 ; j < size ; j++)
scanf("%d", &mat[i][j]) ;
for(i = 0 ; i < size ; i++)
{
for(j = 0 ; j < size ; j++)
{
if(i == j)
if(mat[i][j] != 1)
flag = 0 ;
if(i != j)
if(mat[i][j] != 0)
flag = 0 ;
}
}
if(flag == 1)
printf("\nThe matrix is an unit matrix") ;
else
printf("\nThe matrix is not an unit matrix") ;
getch() ;
}

RUN 1 :
~~~~~~~
Enter size of the square matrix : 3
Enter the elements of the matrix :
1 0 0
0 1 0
0 0 1
The matrix is an unit matrix

RUN 2 :
~~~~~~~
Enter size of the square matrix : 3
Enter the elements of the matrix :
1 2 3
4 1 5
6 7 1
The matrix is not an unit matrix