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Answer 1

+1 A:

You can read about the keyword unsigned in the C++ Reference.

There are two different types in this matter, signed and un-signed. The default for integers is signed which means that they can have negative values.

On a 32-bit system an integer is 32 Bit which means it can contain a value of ~4 Milion.

And when it is signed, this means you need to split it, leaving -2 milions to +2 milions.

When it is unsigned however the value cannot contain any negative numbers, so for integers this would mean 0 to +4 milion.

There is a bit more informationa bout this on Wikipedia.

Filip Ekberg 2010-01-20 08:09:23

I like singed for most things myself. Yummy carbon and carmelization!

Omnifarious 2010-01-20 08:15:00

How about edit typos?... thats what the "edit" button is there for!

Filip Ekberg 2010-01-20 10:16:46

Answer 2

+8 A:

Does the unsigned keyword default to a data type in C++

Yes,signed and unsigned may also be used as standalone type specifiers

The integer data types char, short, long and int can be either signed or unsigned depending on the range of numbers needed to be represented. Signed types can represent both positive and negative values, whereas unsigned types can only represent positive values (and zero).

An unsigned integer containing n bits can have a value between 0 and 2ⁿ - 1 (which is 2ⁿ different values).

However,signed and unsigned may also be used as standalone type specifiers, meaning the same as signed int and unsigned int respectively. The following two declarations are equivalent:

unsigned NextYear;
unsigned int NextYear;

Prasoon Saurav 2010-01-20 08:12:31

Isn't that a "yes", then? It defaults to int, if used without a type?

unwind 2010-01-20 10:19:52

You are right,edited.

Prasoon Saurav 2010-01-20 11:14:51

Answer 3

+7 A:

From the link above:

Several of these types can be modified using the keywords signed, unsigned, short, and long. When one of these type modifiers is used by itself, a data type of int is assumed

This means that you can assume the author is using ints.

futureelite7 2010-01-20 08:14:20

Answer 4

+5 A:

Integer Types:

short            -> signed short
signed short
unsigned short
int              -> signed int
signed int
unsigned int
signed           -> signed int
unsigned         -> unsigned int
long             -> signed long
signed long
unsigned long

Be careful of char:

char  (is signed or unsigned depending on the implmentation)
signed char
unsigned char

Martin York 2010-01-20 08:14:40

@Firas : _I know it is in C_ .Implicit int is neither a part of ISO C99 nor a part of ISO C++

Prasoon Saurav 2010-01-20 08:26:05

Using 'unsigned' (by itself) to declare the 'unsigned int' type is standard in C++. In the current standard: 7.1.5.2 [dcl.simple.type] has a table that identifies each type declaration to the actual type used. That table has a correspondence from 'unsigned' declaration to 'unsigned int' type.

David Rodríguez - dribeas 2010-01-20 08:43:34

Note that char has identical *behavior* to either signed char or unsigned char, but remains a separate type no matter what.

Roger Pate 2010-01-20 09:10:22

@Firas: See Section: 3.9.1 Fundamental types. Paragrah 2: <quote>There are five standard signed integer types : “signed char”, “short int”, “int”, “long int”, and “long long int”.</quote>

Martin York 2010-01-20 14:24:31

Answer 5

A:

Yes, it means unsigned int. It used to be that if you didn't specify a data type in C there were many places where it just assumed int. This was try, for example, of function return types.

This wart has mostly been eradicated, but you are encountering its last vestiges here. IMHO, the code should be fixed to say unsigned int to avoid just the sort of confusion you are experiencing.

Omnifarious 2010-01-20 08:17:32

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