struct and varialbe

Hi,
I'm not very used to the C syntax, so I'm having this probably rather easy to solve problem for someone with experience.
I have a struct that is of the form

Code:

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typedef struct MyStruct{
    uint32_t myVar:2; 
} MyStruct;

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As far as I know the :2 means that I have a myVar that has actually a width of two unit32_t. Is that correct?
Question is, how how can I assign values to one of the 2 single instances of uint32_t?

As you have it myvar is only 2 bits wide.
If you want two integers you need myvar[2];

Oh ok, thanks.
So I can just assign limited values to the integer if its of the form above? (In this case from 0 - 3 ?)

Yes that would be values( 0 - 3 ) for unsigned.

But remember that your struct is actually using an unsigned int to save the first 2 bits,
therefore you're using up memory for no reason ( 30 bit remain unused )

Quote:

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Originally Posted by zu1u

Hi,
... I have a struct that is of the form

Code:

---

typedef struct MyStruct{
    uint32_t myVar:2; 
} MyStruct;

---

...

---

In C99, the only types guaranteed to be supported for bit fields are _Bool, signed int, or unsigned int. Other types may be supported as implementation-defined.

Quote:

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Originally Posted by Sipher

But remember that your struct is actually using an unsigned int to save the first 2 bits,
therefore you're using up memory for no reason ( 30 bit remain unused )

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How do you know the structure will be 32-bits wide? Why could it not be 16-bits or 64-bits or some other width?

Because the type is 32 bits in this example (uint32_t).