练习2-1 编写一个程序一确定分别由signed及unsigned限定的char，short，int及long类型变量的取值范围。采用打印标准头文件中的相应值以及直接计算两种方式实现。通过直接计算来确定浮点类型的取值范围是一项难度很大的任务。

1.打印标准头文件中的相应值

#include <stdio.h>
#include <limits.h>
main()
{
    /* signed types */

    printf("signed char min = %d\n", SCHAR_MIN);
    printf("signed char max = %d\n", SCHAR_MAX);
    printf("signed short min = %d\n", SHRT_MIN);
    printf("signed short max = %d\n", SHRT_MAX);
    printf("signed int min = %d\n", INT_MIN);
    printf("signed int max = %d\n", INT_MAX);
    printf("signed long min = %d\n", LONG_MIN);
    printf("signed long max = %d\n", LONG_MAX);

    /*unsigned types*/
    printf("unsigned char max = %d\n", UCHAR_MAX);
    printf("unsigned short max = %d\n", USHRT_MAX);
    printf("unsigned int max = %d\n", UINT_MAX);
    printf("unsigned long max = %d\n", ULONG_MAX);

    return 0;
}

输出：

 

2.直接计算方式

#include <stdio.h>
/*determine ranges of types*/

main()
{
     /* signed ranges of types*/

    printf(" signed char min = %d \n", -(char)((unsigned char) ~0 >> 1));

    printf(" signed char max = %d \n", (char)((unsigned char) ~0 >> 1));

    printf(" signed short min = %d \n", -(short)((unsigned short) ~0 >> 1));

    printf(" signed short max = %d \n", (short)((unsigned short) ~0 >> 1));

    printf(" signed int min = %d \n", -(int)((unsigned int) ~0 >> 1));

    printf(" signed int max = %d \n", (int)((unsigned int) ~0 >> 1));

    printf(" signed long min = %d \n", -(long)((unsigned long) ~0 >> 1));

    printf(" signed long max = %d \n", (long)((unsigned long) ~0 >> 1));


    /*unsigned types*/

    printf(" unsigned char max = %d \n",(unsigned char) ~0);

    printf(" unsigned int max = %d \n",(unsigned int) ~0);

    printf(" unsigned short max = %d \n",(unsigned short) ~0);

    printf(" unsigned long max = %d \n",(unsigned long) ~0);


    return 0;
}

输出：