C Programming

Initialization of a multidimensional arrays in C/C++

In C/C++, initialization of a multidimensional arrays can have left most dimension as optional. Except the left most dimension, all other dimensions must be specified.

For example, following program fails in compilation because two dimensions are not specified.

#include<stdio.h>
int main()
{
  int a[][][2] = { {{1, 2}, {3, 4}}, 
                   {{5, 6}, {7, 8}}
                 };  // error
  printf("%d", sizeof(a)); 
  getchar();
  return 0;
}

Following 2 programs work without any error.

// Program 1
#include<stdio.h>
int main()
{
  int a[][2] = {{1,2},{3,4}}; // Works
  printf("%d", sizeof(a)); // prints 4*sizeof(int)
  getchar();
  return 0;
}

:::cpp
// Program 2
#include<stdio.h>
int main()
{
  int a[][2][2] = { {{1, 2}, {3, 4}}, 
                     {{5, 6}, {7, 8}}
                   }; // Works
  printf("%d", sizeof(a)); // prints 8*sizeof(int)
  getchar();
  return 0;
}

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