q2.c

#include <stdio.h>

void Identity(int *matrix, size_t size)
{
  for (size_t i = 0; i < size; ++i) {
    for (size_t j = 0; j < size; ++j) {
      matrix[i * size + j] = (i == j) ? 1 : 0;
    }
  }
}

void PrintMatrix(int *matrix, size_t size)
{
  for (size_t i = 0; i < size; ++i) {
    for (size_t j = 0; j < size; ++j) {
      printf("%d", matrix[i * size + j]);
    }
    printf("\n");
  }
}

int main(int argc, char const *argv[])
{
  size_t size = 0;
  printf("Size of matrix: ");
  scanf("%zd", &size);

  int matrix[size][size];
  Identity(&matrix[0][0], size);
  PrintMatrix(&matrix[0][0], size);

  return 0;
}