C语言中基本整型数据类型

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C语言中的基本整型数据类型

整型家族包括字符、短整型、整型、长整型，它们都分为有符号和无符号两种版本

整型值相互之间的大小的规则：

长整型至少应该和整型一样长，而整型至少应该和短整型一样长

一般情况下各种类型在32、64位机上的大小

long,unsigned long pointer为机器全字长，其实也就是这几种类型的大小和CPU的位数是一样的。

下面的程序是在X86架构环境上，使用gcc version 4.7.2 20121109 (Red Hat 4.7.2-8) (GCC)编译得到的

#include <stdio.h>int main(){        printf("the char range is           %-20hhd~%20hhu, size is %u\n", 0x80, 0x7f, sizeof(char));        printf("the usigned char range is   %-20hhu~%20hhu, size is %u\n", 0x0, 0xff, sizeof(unsigned char));        printf("the short range is          %-20hd~%20hu, size is %u\n", 0x8000, 0x7fff, sizeof(short));        printf("the unsigned short range is %-20hu~%20hu, size is %u\n", 0x0, 0xffff, sizeof(unsigned short));        printf("the int range is            %-20d~%20u, size is %u\n", 0x80000000, 0x7fffffff, sizeof(int));        printf("the unsigned int range is   %-20u~%20u, size is %u\n", 0x0, 0xffffffff,  sizeof(unsigned int));        printf("the long range is           %-20ld~%20lu, size is %u\n", 0x80000000, 0x7fffffff, sizeof(long));        printf("the unsigned long range is  %-20lu~%20lu, size is %u\n", 0x0, 0xffffffff, sizeof(unsigned long));        printf("the llong range is          %-20lld~%20llu, size is %u\n", 0x8000000000000000, 0x7fffffffffffffff, sizeof(long long));        printf("the unsigned llong range is %-20lld~%20llu, size is %u\n", 0x0ll, 0xffffffffffffffff, sizeof(unsigned long long));        printf("default constant size is %u %u %u\n", sizeof('b'), sizeof(0x0), sizeof(0x0ll));}

运行结果

the char range is -128 ~ 127, size is 1
the usigned char range is 0 ~ 255, size is 1
the short range is -32768 ~ 32767, size is 2
the unsigned short range is 0 ~ 65535, size is 2
the int range is -2147483648 ~ 2147483647, size is 4
the unsigned int range is 0 ~ 4294967295, size is 4
the long range is -2147483648 ~ 2147483647, size is 4
the unsigned long range is 0 ~ 4294967295, size is 4
the llong range is -9223372036854775808~ 9223372036854775807, size is 8
the unsigned llong range is 0 ~18446744073709551615, size is 8

default constant size is 4 4 8

整型字面值（整型常量）

字面值这个术语是字面值常量的缩写------这是一种实体，指定了自身的值，并且不允许发生改变。

当程序内出现整型常量时，它是属于整型家族类型中的哪一种？答案取决于常量是如何书写的，可以在有些常量的后面添加一个后缀来改变缺省规则。在整数常量后面添加L或l，可以使这个整数被解释为long整型值，字符U或u则用于吧数值指定为unsigned 整型值，如果一个常量后面添加这两个字符中的各一个，那么它就被解释为unsigned long整型值。对于字符常量。它们的类型总是int。不能再它们后面添加unsigned或者long后缀

C语言一般默认整型常量（字符常量/整型常量）类型为int，

如果使用格式字符%llu，printf会认为要输出的这个值的大小为8字节，所以如果对应的参数如果为0x0的话则有可能打印出乱七八糟的东西（因为它读了8个字节而不是4个字节）

另外printf整型变量时，打印的是有符号还是无符号取决于格式字符，与实际传入的参数类型及符号无关。

例如

int i = 0x80001010;

printf("%d\n", i);打印-2147479536

printf("%u\n", i);打印2147487760

printf("%hu\n",i);打印4112高两位被截断，打印的实际是0x1010

printf("%hhu\n",i);打印16高三位被截断，打印的实际是0x10

所以请谨记使用printf打印变量的大小与符号与变量本身无关，即使强转也不行！应选择对应正确的格式字符

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