What does 'var = &Binary[0][0][0][0]' mean in C?

Question

I saw this assignment:

u = &Binary[0][0][0][0]

in a for loop:

for (i = 0, u = &Binary[0][0][0][0]; i < MAX_ADDRESSES; i++, u++)

from this section:

#define ILLEGAL_VALUE 0xFFFF
#define MAX_MODULES 8
#define MAX_SECTORS 16
#define MAX_SYLLABLES 3
#define MAX_WORDS 256
#define MAX_ADDRESSES (MAX_MODULES * MAX_SECTORS * MAX_SYLLABLES * MAX_WORDS)

...

int i;
uint16_t *u;

// Initialize the binary as completely unused.
for (i = 0, u = &Binary[0][0][0][0]; i < MAX_ADDRESSES; i++, u++)
  *u = ILLEGAL_VALUE;

for an assembler.

I am not very familiar with c (or other compiled languages), awk is somewhat similar to c.

In awk var[x] is an array, but this seems not to be an array, or any other variable.

What is this piece of code ' &Binary[0][0][0][0] ' ?

Edit:

Indeed I found this:

typedef uint16_t
    BinaryImage_t[MAX_MODULES][MAX_SECTORS][MAX_SYLLABLES][MAX_WORDS];
#define ILLEGAL_VALUE 0xFFFF

So it is an array after all !

However I am surprised by the ampersand as the first character of the array name ?

Answer 1

Somewhere in your code is likely a declaration for a multi-dimensional array named Binary Most likely a 4-d array of type uint16_t (16-bit unsigned int)

uint16_t Binary[MAX_MODULES][MAX_SECTORS][MAX_SYLLABLES][MAX_WORDS];

This expression: &Binary[0][0][0][0]

is the address of the first element in this multi-dimensional array. While the array is declared as a 4-d array, it appears the for-loop is simply enumerating over all elements in the array via pointer to initialize each with the ILLEGAL_VALUE constant.

For what it's worth, the for-loop could likely be replaced with:

memset(Binary, 0xff, sizeof(Binary));

Answer 2

regarding:

u = &Binary[0][0][0][0]

this means set the contents of u with the address of the very first entry in a 4 dimensional array