what are default integer values?

Question

I read somewhere that default floating point values like 1.2 are double not float.
So what are default integer values like 6 , are they short , int or long?

I heard that range of `short` and `int` is same. so a value bigger than `int` may come under `long` but what about small values, as they can be `short` and `int` both. — kevin gomes, Jan 27 '14 at 14:11
By the way, these are normally called "constant expressions" or "integer constants". The phrase "default values" normally implies a standard value like `0` or `0.0` which happens in certain cases (such as defining a `static` variable without an initializer) — Brandin, Jan 27 '14 at 14:33
After reading the answers below, test yourself and see if you can explain why `sizeof(4294967295u)` < `sizeof(2147483648)` :) — Lundin, Jan 27 '14 at 14:59

interjay · Accepted Answer · 2014-01-27T14:16:10.753

7

The type of integer literals given in base 10 is the first type in the following list in which their value can fit:

int
long int
long long int

For octal and hexadecimal literals, unsigned types will be considered as well, in the following order:

int
unsigned int
long int
unsigned long int
long long int
unsigned long long int

You can specify a u suffix to force unsigned types, an l suffix to force long or long long, or an ll suffix to force long long.

Reference: C99, 6.4.4.1p5

edited Jan 27 '14 at 14:16

answered Jan 27 '14 at 14:09

interjay

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what suffix for `short` – kevin gomes Jan 27 '14 at 14:13
@kevingomes There is no suffix for `short`. But if you need it (and you usually don't because conversion is automatic), you can cast to `short`. – interjay Jan 27 '14 at 14:14

legends2k · Answer 2 · 2014-06-11T06:56:57.670

Just if someone is interested:

C11 §6.4.4.1/5:

The type of an integer constant is the first of the corresponding list in which its value can be represented.

---------------------------------------------------------------------------
Suffix        Decimal Constant              Octal/Hexadecimal Constant
---------------------------------------------------------------------------
none          int                           int
              long int                      unsigned int
              long long int                 unsigned long int
                                            long long int
                                            unsigned long long int
---------------------------------------------------------------------------
u or U        unsigned int                  unsigned int
              unsigned long int             unsigned long int
              unsigned long long int        unsigned long long int
---------------------------------------------------------------------------
l or L        long int                      long int
              long long int                 unsigned long int
                                            long long int
                                            unsigned long long int
---------------------------------------------------------------------------
Both u or U   unsigned long int             unsigned long int
and l or L    unsigned long long int        unsigned long long int
---------------------------------------------------------------------------
ll or LL      long long int                 long long int
                                            unsigend long long int
---------------------------------------------------------------------------
Both u or U   unsigned long long int        unsigned long long int
and ll or LL
---------------------------------------------------------------------------

As for the prefix §6.4.4.1/3:

A decimal constant begins with a nonzero digit and consists of a sequence of decimal digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed by a sequence of the decimal digits and the letters a (or A) through f (or F) with values 10 through 15 respectively.

FYI, I used a modified version of your table [here](http://stackoverflow.com/a/24148306/1708801). — Shafik Yaghmour, Jun 10 '14 at 18:50

Shafik Yaghmour · Answer 3 · 2014-01-27T14:52:08.130

2

There are three types of integer literals(or integer constants in the standards terminology): decimal, octal or hex and the rule are slightly different for your specific example 6 would be int but in general for decimal constants without a suffix(u, U, l, L, ll, LL) it will be based on which type can represent the value which is covered in the draft C99 standard section 6.4.4.1 Integer constants paragraph 5 which says:

The type of an integer literal is the first of the corresponding list in which its value can be represented.

so for a decimal literal without a suffix the types would be the first of:

int
long int
long long int

and for octal and hex the types would be the first of:

int
unsigned int
long int
unsigned long int
long long int
unsigned long long int

edited Jan 27 '14 at 14:52

answered Jan 27 '14 at 14:10

Shafik Yaghmour

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"Integer literals", not "constants", I think. – Kerrek SB Jan 27 '14 at 14:12
why 6 is `int` ,it can also be `short` – kevin gomes Jan 27 '14 at 14:12
@KerrekSB: `C11` calls them constants – legends2k Jan 27 '14 at 14:13
@KerrekSB literal is C++ it comes under the integer constants section in C99. – Shafik Yaghmour Jan 27 '14 at 14:13
Sorry, my bad. I always think these questions are about C++ when in fact they are about C. Indeed, in C the only constants are literals, so that makes sense. – Kerrek SB Jan 27 '14 at 14:15
1

Still, it might be wise to refer to them as _integer literals_, then everyone knows what you mean. "Constants" might mean a whole lot of different things in C, the term is simply not helpful. – Lundin Jan 27 '14 at 14:44

what are default integer values?

3 Answers3

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