Thread: passing multidimensional array

hello,
this program is supposed to convert an array with dec values to binary. it compiles without errors but then it gives a segfault:

Code:

#include <stdio.h>

void dectobin (int *dec, int **bit);

int main( void ) {

int dec[8] = { 12,13,14,15,16,17,18,19 } ;
int **bit ;

dectobin (dec, bit);

return 0;
}

void dectobin (int *dec, int **bit) {

 int j,i;
   
 for( i = 0; i < 8; i++ ) {
	for(j=7;j>=0;j--) 
      {
	bit[i][j] = (dec[i] % 2);
	dec[i] /=2;
	}
      }
      
 for( i = 0 ; i < 8; i++ ) {
 
	printf("\n");
	
	for(j=0; j<8; j++)
	printf("%d",bit[i][j]);
	
	}
}

thank you , it works well , although i still have a question . If i just pass the bit[][] to the function it will say :

Code:

invalid use of array with unspecified bounds

That means i have to pass the array with specified bounds like bit[][8] ? Why is that? why doesn't bit[][] work?

It doesn't work because of how the compiler and computer give memory to the array. The 2-d array is nothing more than a group of 1d arrays one after the other. It needs a number in the second bracket to know how long to make each segment. (Hope that made sense). If you don't want to have to worry about the size of your array, just malloc() it instead.