what is the unsigned datatype?

Question

I've seen this unsigned "typeless" type used a couple of times, but never seen an explanation for it. I suppose there's a corresponding signed type. Here's an example:

static unsigned long next = 1;
/* RAND_MAX assumed to be 32767 */
int myrand(void) {
    next = next * 1103515245 + 12345;
    return((unsigned)(next/65536) % 32768);
}
void mysrand(unsigned seed) {
    next = seed;
}

What I have gathered so far:
- on my system, sizeof(unsigned) = 4 (hints at a 32-bit unsigned int)
- it might be used as a shorthand for casting another type to the unsigned version:

signed long int i = -42;
printf("%u\n", (unsigned)i);

Is this ANSI C, or just a compiler extension?

Answer 1

unsigned really is a shorthand for unsigned int, and so defined in standard C.

Answer 2

unsigned means unsigned int. signed means signed int. using just unsigned is a lazy way of declaring an unsigned int in C. Yes this is ANSI.

Answer 3

in C, unsigned is a shortcut for unsigned int.

You have the same for long that is a shortcut for long int

And it is also possible to declare a unsigned long (it will be a unsigned long int).

This is in the ANSI standard

Answer 4

Historically in C, if you omitted a datatype "int" was assumed. So "unsigned" is a shorthand for "unsigned int". This has been considered bad practice for a long time, but there is still a fair amount of code out there that uses it.