How do unsigned integers work

Question

As the title suggests, I am curious about how an unsigned int (or things like NSUInteger, u_int_blah, but I assume these are all

Answer 1

When a unsigned comparing with signed, they will all be cast into unsigned. The procedure is relative to how the data is stored in memory. In binary, a minus number( like -3), will be stored like :

-3 : 1111 1111 1111 1101
3  : 0000 0000 0000 0011

you can tell that -3 can be like :

// result  : 0000 0000 0000 0011

result = for_every_bit_of_3( not **ThisBit** );  
// result  : 1111 1111 1111 1100 

result = result + 1;
// result  : 1111 1111 1111 1101 

So the loop:

for (unsigned int x = 5; x > -10; x--) {
    // will x ever reach below zero, or will the loop terminate
}

will be like

// 4,294,967,286 is what -10 cast to unsigned
for (unsigned int x = 5; x > 4294967286; x--) {
    // will x ever reach below zero, or will the loop terminate
}