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

img

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

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#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

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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则用于把数值指定为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

printf格式化的原则

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打印整型变量时，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

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int i = 0x80001010;
printf("%d\n", i);  //打印-2147479536 
printf("%u\n", i);  //打印2147487760
printf("%hu\n",i);  //打印4112，高位两字节被截断，打印的实际是0x1010

printf("%hhu\n",i); //打印16，高位三字节被截断，打印的实际是0x10

所以请谨记使用printf打印变量的值与该变量的符号和变量本身无关，即使强转也不行！是有printf的格式字符决定的，应选择对应正确的格式字符