Tipos aritmeticos

(Véase también type para la descripción general del sistema de tipos y la lista de utilidades relacionadas con el tipo que proporciona la biblioteca C)

[editar] Tipos de carácter

• signed char - tipo para la representación de caracteres con signo.
• unsigned char - tipo para la representación de caracteres sin signo. También se utiliza para inspeccionar representaciones de objetos (memoria bruta).
• char - tipo para la representación de caracteres. Equivalente a un signed char o a un unsigned char (el cual está definido por la implementación y puede ser controlado por un modificador en la línea de comandos del compilador), pero los char son de un un tipo distinto, diferente tanto del signed char como del unsigned char.

Tenga en cuenta que la biblioteca estándar también define los nombres de los [[../typedef} wchar_t , char16_t, y char32_t (desde C11) para representar caracteres anchos.

Tipos de enteros

• short int (también accesible como short, puede usar el término clave signed)
• unsigned short int (también accesible como unsigned short)
• int (también accesible como signed int)

Este es el tipo de entero más óptimo para la plataforma, y se garantiza que sea de al menos 16 bits. La mayoría de los sistemas actuales utilizan 32 bits (ver Modelos de datos más abajo).

• unsigned int (también accesible como unsigned), la contraparte sin signo de {c|int]], que implementa la aritmética de módulos. Adecuado para manipulaciones de bits.
• long int (también accesible como long)
• unsigned long int (también accesible como unsigned long)

Nota: al igual que con todos los especificadores de tipo, se permite cualquier orden: unsigned long int y long int unsigned long} nombran el mismo tipo.

La siguiente tabla resume todos los tipos de enteros disponibles y sus propiedades:

Además del mínimo número de bits, el Estándar C garantiza que

1 == sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long) <= sizeof(long long).

Nota: esto permite el caso extremo en el que los bytes tengan un tamaño de 64 bits, todos los tipos (incluyendo char) tienen un ancho de 64 bits, y sizeof devuelve 1 para cada tipo.

Nota: la aritmética de números enteros se define de forma diferente para los tipos de números enteros con y sin signo. Véase operadores aritmeticos}, en particular desbordamientos de enteros.

[editar] Data models

The choices made by each implementation about the sizes of the fundamental types are collectively known as data model. Four data models found wide acceptance:

32 bit systems:

• LP32 or 2/4/4 (int is 16-bit, long and pointer are 32-bit)

• Win16 API

• ILP32 or 4/4/4 (int, long, and pointer are 32-bit);

• Win32 API
• Unix and Unix-like systems (Linux, Mac OS X)

64 bit systems:

• LLP64 or 4/4/8 (int and long are 32-bit, pointer is 64-bit)

• Win64 API

• LP64 or 4/8/8 (int is 32-bit, long and pointer are 64-bit)

• Unix and Unix-like systems (Linux, Mac OS X)

Other models are very rare. For example, ILP64 (8/8/8: int, long, and pointer are 64-bit) only appeared in some early 64-bit Unix systems (e.g. Unicos on Cray).

Note that exact-width integer types are available in <stdint.h> since C99

[editar] Real floating types

C has three types for representing real floating-point values:

• float - single precision floating point type. Matches IEEE-754 32 bit floating point type if supported.
• double - double precision floating point type. Matches IEEE-754 64 bit floating point type if supported
• long double - extended precision floating point type. Matches IEEE-754 extended floating-point type if supported, otherwise matches some non-standard extended floating-point type as long as its precision is better than double and range is at least as good as double, otherwise matches the type double. Some x86 and x86_64 implementations use the 80-bit x87 floating point type.

Floating-point types may support special values:

• infinity (positive and negative), see INFINITY
• the negative zero, -0.0. It compares equal to the positive zero, but is meaningful in some arithmetic operations, e.g. 1.0/0.0 == INFINITY, but 1.0/-0.0 == -INFINITY)
• not-a-number (NaN), which does not compare equal with anything (including itself). Multiple bit patterns represent NaNs, see nan, NAN. Note that C takes no special notice of signalling NaNs (specified by IEEE-754), and treates all NaNs as quiet.

Real floating-point numbers may be used with arithmetic operators + - / * and various mathematical functions from math.h. Both built-in operators and library functions may raise floating-point exceptions and set errno as described in math_errhandling

Floating-point expressions may have greater range and precision than indicated by their types, see FLT_EVAL_METHOD. Assignment, return, and cast force the range and precision to the one associated with the declared type.

Floating-point expressions may also be contracted, that is, calculated as if all intermediate values have infinite range and precision, see #pragma STDC FP_CONTRACT.

Some operations on floating-point numbers are affected by and modify the state of the floating-point environment (most notably, the rounding direction)

Implicit conversions are defined between real floating types and integer, complex, and imaginary types.

See Limits of floating point types and the math.h library for additional details, limits, and properties of the floating-point types.

#include <complex.h>
#include <stdio.h>
int main(void)
{
    double complex z = 1 + 2*I;
    z = 1/z;
    printf("1/(1.0+2.0i) = %.1f%+.1fi\n", creal(z), cimag(z));
}

1/(1.0+2.0i) = 0.2-0.4i

float a[4] = {1, 2, 3, 4};
float complex z1, z2;
memcpy(&z1, a, sizeof z1); // z1 becomes 1.0 + 2.0i
memcpy(&z2, a+2, sizeof z2); // z2 becomes 3.0 + 4.0i

#include <stdio.h>
#include <complex.h>
#include <math.h>
int main(void)
{
   double complex z = (1 + 0*I) * (INFINITY + I*INFINITY);
// textbook formula would give
// (1+i0)(∞+i∞) ⇒ (1×∞ – 0×∞) + i(0×∞+1×∞) ⇒ NaN + I*NaN
// but C gives a complex infinity
   printf("%f + i*%f\n", creal(z), cimag(z));
 
// textbook formula would give
// cexp(∞+iNaN) ⇒ exp(∞)×(cis(NaN)) ⇒ NaN + I*NaN
// but C gives  ±∞+i*nan
   double complex y = cexp(INFINITY + I*NAN);
   printf("%f + i*%f\n", creal(y), cimag(y));
 
}

inf + i*inf 
inf + i*nan

#include <complex.h>
#include <stdio.h>
int main(void)
{
    double imaginary z = 3*I;
    z = 1/z;
    printf("1/(3.0i) = %+.1fi\n", cimag(z));
}

1/(3.0i) = -0.3i

[editar] Keywords

char, int, short, long, signed, unsigned, float, double. _Bool, _Complex, _Imaginary

[editar] Range of values

The following table provides a reference for the limits of common numeric representations. As the C Standard allows any signed integer representation, the table gives both the minimum guaranteed requirements (which correspond to the limits of one's complement or sign-and-magnitude) and the limits of the most commonly used implementation, two's complement. All popular data models (including all of ILP32, LP32, LP64, LLP64) use two's complement representation, though.

Note: actual (as opposed to guaranteed minimal) ranges are available in the library headers <limits.h> and <float.h>

[editar] See also