K& R答案书中的问题 [英] problem in K&R answer book
问题描述
大家好
这是K& R给答案书中给出的程序
============= =======================
#include< stdio.h>
int main（）
{
printf（" signed char =％d"， - （char）（（unsigned char）~0>> 1） ）;
printf（" signed char =％d"，（char）（（unsigned char）~0>> 1））;
返回0;
}
============================= =====
这是打印我们可以存储在签名字符中的最大值..
这个输出是
-127
127
但是我们可以将-128作为签名字符中的值存储在< limits.h>
#define SCHAR_MIN（-128）
为什么在最着名的K& R答案书中以这种方式给出
我是错的还是程序错了..
PLZ帮帮我
问候
prem
Hi everyone
this is the program given in answer book to K&R
====================================
#include <stdio.h>
int main()
{
printf (" signed char = %d", -(char) ((unsigned char) ~0 >> 1));
printf (" signed char = %d", (char) ((unsigned char) ~0 >> 1));
return 0;
}
==================================
This is to print the maximum value we can store in a signed char..
the output of this is
-127
127
but we can store -128 as the value in a signed char and also in <limits.h>
# define SCHAR_MIN (-128)
why is it given in that way in the most famous K&R answerbook
am i wrong or the program is wrong..
plz help me
regards
prem
推荐答案
Prem Mallappa写道：
Prem Mallappa wrote:
大家好
这是K& R给答案书中给出的程序
= ===================================
#include< stdio.h>
int main（）
{
printf（" signed char =％d"， - （char）（（unsigned char）~0>> 1））;
printf（" signed char =％d"，（char）（（unsigned char）〜 0>> 1））;
返回0;
}
===================== =============
这是打印我们可以存储在签名字符中的最大值..
这个输出是
-127
127
但是我们可以将-128作为值存储在一个有符号的char中，也可以存储在< limits.h>
#define SCHAR_MIN（-128）
为什么在最着名的K& R答案书中以这种方式给出
我错了或程序错了..
PLZ帮帮我
Hi everyone
this is the program given in answer book to K&R
====================================
#include <stdio.h>
int main()
{
printf (" signed char = %d", -(char) ((unsigned char) ~0 >> 1));
printf (" signed char = %d", (char) ((unsigned char) ~0 >> 1));
return 0;
}
==================================
This is to print the maximum value we can store in a signed char..
the output of this is
-127
127
but we can store -128 as the value in a signed char and also in <limits.h>
# define SCHAR_MIN (-128)
why is it given in that way in the most famous K&R answerbook
am i wrong or the program is wrong..
plz help me
-127是SCHAR_MIN的允许值。
我不知道你指的是哪个K& R问题。
-
pete
-127 is an allowable value for SCHAR_MIN.
I don''t know which K&R problem you are refering to.
--
pete
pete写道：
pete wrote:
Prem Mallappa写道：
Prem Mallappa wrote:
大家好
这是程序在给K& R的答案书中给出了
================================== ==
#include< stdio.h>
int main（）
{
printf（" signed char =％d"， - （char）（（unsigned char）~0>> 1））;
printf（" signed char =％d"，（char）（（unsigned char）〜 0>> 1））;
返回0;
}
===================== =============
这是打印我们可以存储在签名字符中的最大值..
这个输出是
-127
127
但是我们可以将-128作为值存储在签名字符中，也可以存储在
< limits.h>
#define SCHAR_MIN（ - 128）
为什么在最着名的K& R答案书中以这种方式给出
我错了或程序错了..
PLZ帮帮我
Hi everyone
this is the program given in answer book to K&R
====================================
#include <stdio.h>
int main()
{
printf (" signed char = %d", -(char) ((unsigned char) ~0 >> 1));
printf (" signed char = %d", (char) ((unsigned char) ~0 >> 1));
return 0;
}
==================================
This is to print the maximum value we can store in a signed char..
the output of this is
-127
127
but we can store -128 as the value in a signed char and also in
<limits.h>
# define SCHAR_MIN (-128)
why is it given in that way in the most famous K&R answerbook
am i wrong or the program is wrong..
plz help me
-127是SCHAR_MIN允许的值。
我不知道你指的是哪个K& R问题。
-127 is an allowable value for SCHAR_MIN.
I don''t know which K&R problem you are refering to.
运动C编程语言2-1：由Kernighan和Ritchie ...
- 写一个程序来确定Char，short，int的范围......两者都签了
和未签名的，通过打印批准来自标准标题的priate值和
直接计算..
Excercise 2-1 of C programming Language : by Kernighan and Ritchie...
-- Write a program to determine the ranges of Char, short, int.. both signed
and unsigned, by printing appropriate values from standard headers and by
direct computation..
Prem Mallappa写道：
Prem Mallappa wrote:
大家好。
这是给K& R答案书中给出的程序
======================== ============
#include< stdio.h>
int main（）
{
printf（" signed char =％d"， - （char）（（unsigned char）~0>> 1））;
printf（" signed char =％d"，（char）（（unsigned char）〜 0>> 1））;
返回0;
}
===================== =============
这是打印我们可以存储在签名字符中的最大值..
这个输出是
-127
127
但是我们可以将-128作为值存储在一个有符号的char中，也可以存储在< limits.h>
#define SCHAR_MIN（-128）
为什么在最着名的K& R答案书中以这种方式给出
我错了或程序错了..
Hi everyone
this is the program given in answer book to K&R
====================================
#include <stdio.h>
int main()
{
printf (" signed char = %d", -(char) ((unsigned char) ~0 >> 1));
printf (" signed char = %d", (char) ((unsigned char) ~0 >> 1));
return 0;
}
==================================
This is to print the maximum value we can store in a signed char..
the output of this is
-127
127
but we can store -128 as the value in a signed char and also in <limits.h>
# define SCHAR_MIN (-128)
why is it given in that way in the most famous K&R answerbook
am i wrong or the program is wrong..
（1）它适合某些机器;其他人错了
（2）假设（char）与（签名字符）相同是错误的
（3）不终止最后一个是错误的带有
行终止字符（''\ n''）的输出行。
试试这个：
#include< stdio.h>
#include< limits.h>
int main（）
{
printf（"％d \ n"，
（有符号字符）（（无符号字符）1<<（CHAR_BIT - 1）））;
printf（" signed char =％d"，
- （signed char）（（unsigned char）~0>> 1））;
printf（" signed char =％d \ n"，
（signed char）（（unsigned char）~0>> 1））;
返回0;
}
-
Martin Ambuhl
(1) It''s right for some machines; wrong for others
(2) It is wrong in assuming that (char) is the same as (signed char)
(3) It is wrong in not terminating the last line of output with a
line-termination character (''\n'').
Try this:
#include <stdio.h>
#include <limits.h>
int main()
{
printf(" %d\n",
(signed char) ((unsigned char) 1 << (CHAR_BIT - 1)));
printf(" signed char = %d",
-(signed char) ((unsigned char) ~0 >> 1));
printf(" signed char = %d\n",
(signed char) ((unsigned char) ~0 >> 1));
return 0;
}
--
Martin Ambuhl
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