bits like int x:4

[esler]

hi

i want to create an unsigned integer array with 10 members each of them is 4 bit.
for example
unsigned int x:4; create an int element with 4 bit ,so 0 to 15 can be assgined t ox

how can i create an array like i explain above

[Magos]

As far as I know, you cannot create your own sized datatypes. What you could do is use bitshifting and masking to store several of your 4bitIntegers in one larger datatype.

ie: a char is 8bit (which means you can store 2 4bitInts in it)

To get the first int:

((CharVar & 0xF0) >> 4)

To get the second int4 (4-bit int):

(CharVar & 0x0F)

To store the first int4:

CharVar = (CharVar & 0x0F) | ((Int4 << 4) & 0xF0)

To store the second int4:

CharVar = (CharVar & 0xF0) | (Int4 & 0x0F)

[foniks munkee]

The format of the code that you are using looks a bit like bit fields.
EG:

struct foo 
{
   unsigned int x     : 1;
   unsigned int y     : 4;
};

..but this doesn't work with arrays. What is it that you need to do exactly?

[esler]

foniks munkee said that
"..but this doesn't work with arrays. What is it that you need to do exactly?"

for example 10000 students at a university . i want to manipulate their grades . a student can take 5 lesson ,and each lesson have 2 midterms,2quiz and a final. the range for mid quiz and finals are 0-100 ,so if i use int for hold grades it wastes the memory so much . For 6 bit is enough to hold mid grades...

i think it is more clear

[Shiro]

>so if i use int for hold grades it wastes the memory so much

For an application like you're working on, I wouldn't care about memory. I guess you're working on a PC which has I guess, lots of memory.

Instead of an unsigned int, you could use an unsigned char.

[foniks munkee]

Well, if you have to store the students name with their score you could use an array of structures and use bit fields to store the scores.