Why can I work with int> +32767?

Question

I can read that int range (signed) from [-32767, +32767] but I can say for example

int a=70000; int b=71000; int c=a+b; printf("%i", c); return 0; 

And the result is 141000 (correct). Shouldn't the debugger tell me "this operation is out of range" or something like that?

I believe this should be with me, ignoring the basics of C programming, but not one of the books I'm reading now says anything about this "problem."

EDIT: 2147483647 seems to be an upper limit, thanks. If the sum exceeds this number, the result is negative, expected, but if it is a subtraction, for example: 2147483649-2147483647 = 2 , the result will still be good. I mean, why is the value 2147483649 true for this purpose (or at least it seems to me)?

Answer 1

You misunderstood. The standard ensures that a int contains [-32767, +32767], but is allowed to hold more. (In particular, almost every compiler that you most likely use allows you to use the range [-2147483648, 2147483647]).

There is one more problem. If you assign the value assigned to a and b more, you probably won't get any warnings or errors. Integer overflow causes "undefined behavior", and literally everything is allowed.

Answer 2

Range [-32767, +32767] is the required minimum range. Implementations are allowed to provide a larger range.

Answer 3

In C ++, int has a length of at least 16 bits, but usually 32 bits on modern hardware. You can write INT_MIN and INT_MAX and test yourself.

Please note that signed integer overflow is undefined behavior , you are not guaranteed to receive a warning, except, possibly, high compiler warnings and debug mode.

Answer 4

All types are compiler dependent. int used as the "native word" of the base equipment, which in 16-bit systems meant that int was 16 bits (which leads to a range from -32 to + 32 k). When 32-bit systems began to appear, then int naturally followed and became 32 bits, which can store values ​​from -2 to +2 billion.

However, this use of the "native word" for int did not follow when 64-bit systems appeared; I don’t know a 64-bit system or compiler with an int 64 bits.

See this link of integer types for more information.

Answer 5

If int is four bytes, then unsigned is 4294967295, signed max. 2147483647 and signed by min. -2147483648

 unsigned int ui = ~0; int max = ui>>1; int min = ~max; int size = sizeof(max); 

Answer 6

While the standard ensures that the int size must be 16 bits, it is usually implemented as a 32-bit value.

Answer 7

The size of the int (and the maximum value it can hold) depends on the compiler and the computer you are using. There is no guarantee that it will have 2 bytes or 4 bytes, but for C ++ variables there is a guaranteed minimum size.

You can see the list of minimum sizes for C ++ types on this page: http://www.cplusplus.com/doc/tutorial/variables/