To find the given matrix is a unit matrix (or) not

Program:

#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();
}

Output:

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