What is the purpose of the & in this struct call?

Question

I am having trouble understanding what the purpose of the & means in this if statement. Would anyone be willing to point me in the right direction? I thought struct calls go as follows

car -> model == "jeep"

This is what I am having confusion about:

if ((x->status & 1) == 0){
...
}

So it would & status in this case? For instance, with the care model if there was a call if((car -> model & jeep) != jeep) { return 1; } — coolkitty112, Oct 21 '22 at 03:14
`car -> model == "jeep"` note that this is wrong. Learn C strings. — hyde, Oct 21 '22 at 04:23

score 1 · Answer 1 · answered Oct 21 '22 at 03:29

1

if ((x->status & 1) == 0){ ... }

This code retrieves the value of the status field from the struct pointed to by x, and performs a bitwise and operation against the constant 1, which has the effect of masking off all but the least significant bit. As a result, this code is checking whether the least-significant bit of the field's value is zero.

answered Oct 21 '22 at 03:29

Dan Bonachea

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Thank you so much, this clears up so much : ) – coolkitty112 Oct 21 '22 at 04:35

score 1 · Answer 2 · answered Oct 21 '22 at 04:27

This

if ((x->status & 1) == 0){ ... }

Is same as

unsigned status = x->status;
unsigned status_bit0 = status & 1;
if (status_bit0 == 0) { ... }

And single & with two operands (on both sides) is bitwise AND operator, not to be confused with unary & which is address-of operator and completely unrelated. Learn binary numbers to understand what bitwise AND is and how it can be used to extract a single bit, that's too broad a subject for this answer.

Also note that unsigned may be wrong type, use what ever is the type of the strict field.

Hi, thank you so much, this does make it more clear : ) – coolkitty112 Oct 21 '22 at 04:35 — coolkitty112, Oct 21 '22 at 04:35

What is the purpose of the & in this struct call?

2 Answers2