Originally Posted by Mac.Z

Hello,
I'm getting started with C++ and have some questions about the variable types:

1)The size of a variable type, is it defined by the compiler or computer or both? and why it differ from one to another?

2)Isn't short int supposed to hold smaller data than int can hold and the same with int and long it, then why sometimes the sizez of data that both of them can hold(short int & int or int & long it) are equal ??
on my pc with Microsoft Visal C++:

Help with Code Tags

c Syntax (Toggle Plain Text)

    cout<< "int: " <<sizeof(int) <<"\n";
    cout<< "short int: " <<sizeof(short int) <<"\n";

cout<< "int: " <<sizeof(int) <<"\n"; cout<< "short int: " <<sizeof(short int) <<"\n";

both can hold 2 bytes only, then what's the point of having short int? the same applies to double & long double..both can hold the same size of data too.

3)For me, "unsigned long int" can hold 4 bytes, it's mentioned that maximum value it can hold is "4,294,967,295" what if I wanted to input a bigger number?what should I use?

4)For following code:

Help with Code Tags

c Syntax (Toggle Plain Text)

unsigned int c;
cout <<"Enter c: ";
cin >>c;
cout <<c <<endl;

unsigned int c; cout <<"Enter c: "; cin >>c; cout <<c <<endl;

what does the program do when I enter I negative value ? I tried -1 and the output was:4294967295..how "-1" was processed? and why it didn't get refused by the program ?!!!

5)For the following code:

Help with Code Tags

c Syntax (Toggle Plain Text)

double c;
cout <<"Enter C: ";
cin>>c;
cout <<c <<endl;

double c; cout <<"Enter C: "; cin>>c; cout <<c <<endl;

What does the program do when I enter a value bigger than it can hold ? I tried 1000000( one million) and the output was:"1e+006", how that value was processed ?

any help would be much appreciated

thanks

Originally Posted by dwks

The way most implementations represent negative numbers means that overflow (the maximum value +1) and underflow (the minimum value, in this case 0, -1) simply wrap. This is standard for underflow for unsigned types, I think, but is otherwise undefined. You created underflow, and the value wrapped to the highest possible value.


It would wrap as many times as nessesary. For example, if it can hold values from 0 to 10, and you enter 43, you would end up with 3. Think of it as the value you assigned to it modulo the maximum value (for unsigned types).

Originally Posted by Mac.Z

but this is not the case with float or int ..I tried to input a value bigger than the maximum one for a specific variable then followed it by another variable but couldn't figure out how the wrapping has been done.