读入十六进制值会在C ++中给出错误的数字

Question

I am trying to read in a hex value using the following code. It is supposed to read in a value from dataFile and the value is supposed to be "810c0001".

int in;
dataFile>>hex>>in>>dec;
cout <<"I just wrote the value: "<<hex<<in<<dec<<endl;

After I run the program the output is shown as "I just wrote the value: 7fffffff". I noticed this problem only occurs when the most significant bit is filled. If I change the inputs '8'to a '7' I get the correct output of: "I just wrote the value: 710c0001" What are some things I can do to read in the correct value? Thank you

Answer 1

That's because int size is 4bytes which means it can only store values from -2,147,483,648 to 2,147,483,647.

7fffffff=2,147,483,647

The value 0x810c0001 is out of range. You can change the variable type to unsigned int to be able to store larger values in a case that you only care about positive numbers.