Passing functions call by value?

I was doing a book example showing passing function pointers. Out of curiosity I took out the pointer syntax and it still works. Does that mean that the function is being passed call by value?

Code:

---

#include <stdio.h>

#define SIZE 10

void bubble( int [], const int, int (*)( int, int ) );
int ascending( int, int );
int descending( int, int );

int main()
{

        int order,
            counter,
            a[ SIZE ] = { 2, 6, 4, 8, 10, 12 , 89, 68, 45, 37 };

        printf( "Enter 1 to sort in ascending order,\n"
                  "Enter 2 to sort ind escending order: " );
        scanf( "%d", &order );
        printf( "\nData items in original order\n" );

        for ( counter = 0; counter < SIZE; counter++ )
                printf( "%5d", a[ counter ] );

        if ( order == 1 ) {
                bubble( a, SIZE, ascending );
                printf( "\nData items in ascending order\n" );
        }
        else {
                bubble( a, SIZE, descending );
                printf( "\nData items in descending order\n" );
        }

        for ( counter = 0; counter < SIZE; counter++ )
                printf( "%5d", a [counter ] );

        printf( "\n" );

        return 0;
}


//-----------------------------------------------It was ( *compare )( int, int )------------------------------
void bubble( int work[], const int size, int (compare)( int, int ) )
{
        int pass, count;

        void swap( int *, int * );

        for ( pass = 1; pass < size; pass++ )

                for ( count = 0; count < size - 1; count++ )

                        if ( (compare)( work[ count ], work[ count + 1 ] ) )
                                swap( &work[ count ], &work[ count + 1 ] );
}



void swap( int *element1Ptr, int *element2Ptr )
{
        int temp;

        temp = *element1Ptr;
        *element1Ptr = *element2Ptr;
        *element2Ptr = temp;
}



int ascending( int a, int b )
{
        return b < a;

}


int descending( int a, int b )
{
        return b > a;
}

---

It's a piece of syntactic sugar -- any function parameter that is itself a function is actually interpreted as a pointer to function (much like your int work[] is actually converted to int *work in the same prototype there). And there's a corresponding piece of syntactic sugar on the other side -- even though compare is a function pointer, you don't need to dereference it to call the function to which it points; using it as a function call is enough.

As as for tips...
I suggest not putting prototypes inside functions. They go to the top of the file or inside headers; nowhere else.
Then, do not strip the parameter names from the prototypes.