How would you set a variable to the largest number possible in C?

Question

How would you set a variable to equal infinity (or any guaranteed largest number value) in C?

Answer 1

Another portable way to get maximum value of integer:

Unsigned integer

unsigned int uMax = (unsigned int)~0;

Signed integer

signed int iMax = (unsigned int)~0 >> 1;

Explanation

• ~0 -> setting all bits to one
• >> 1 -> erasing sign bit, by shifting all bits to the right by one position
• (unsigned int) typecasting to unsigned int after bits inversion instead of using ~0U, because C doesn't have a suffix for short,char literals (everything smaller than int in general)

So for biggest possible char value - just change in formula typecasting to unsigned char and etc.

Bonus - minimum value of signed int

Simply just invert all bits once more in max signed int expression:

signed int iMin = ~((unsigned int)~0 >> 1);

That sets first sign bit to one and the rest bits - to zero