Question

Here is MSDN link
From http://msdn.microsoft.com/en-us/library/s3f49ktz(v=VS.80).aspx

It says:
unsigned int : 4byte
Range of Value 0 to 4,294,967,295

Hence my test code:

void main(void) 
{       
    unsigned int sum;   //4byte, 32bit
    sum = 2147483648;  //2^31 represent by 1 followed by 31 0s
    printf("sum is %d\n",sum); 
    sum = sum -1 ;     //2^31-1 represent by 0 followed by 31 1s
    printf("sum is %d\n",sum);
    getchar();
} 

I am sure 4,294,967,295=2^32-1, printf will print “0”, dump most significant bit
I think MSDN should wrote range of value: 0 to 2147483647
Is that right?

Answer 1

That’s incorrect, if you want to get 4b you should do

unsigned int sum;
sum = 0;
sum -= 1;

Alternatively

unsigned int sum = -1; // will give the same result

This should give you the correct max value for an unsigned int (as hackish as that is). Also as others pointed out you should use %u as the formatter in your printf so that the value gets interpreted correctly.

An unsigned int uses all bits as magnitude bits so the leading bit is no longer considered a sign bit so that becomes 2^32 – 1 instead of just 2^31 – 1