C EOF符号值和带符号的字符 [英] C EOF symbolic value and signed character

问题描述

今天，当我想到一个我无法用自己的能力解决的想法时，我只是躺在床上思考编程知识。

today i just lay on my bed meditating programming stuff when an idea flows into my mind which i can't solve with my own ability.Below is the Question.

为什么-1？通常getchar（）返回一个值范围是0到127，因为这些值对应于标准字符集，但是如果系统识别扩展字符集，它可能返回0到255之间的值。在这两种情况下，值-1都不对应任何字符，因此可以用来表示文件结尾。

1。）对于上面的语句是因为我记得除了带符号的整数外，带符号的字符也是C中存在的一种变量，因此这意味着可以使用-128到127之间的值。但是为什么书中提到-1并不与任何字符使用相抵触

1.)It is weird for the statement above because i remember besides signed integer , signed character is also one type of variable exist in C , so that's mean the value from -128 to 127 can be used.But why still the book mention -1 does not contradict to any character use for keyboard input??

推荐答案

标准不是说它是 -1 。

EOF 扩展为一个整数常量表达式，类型为int和
a负值，它由多个函数返回以指示
文件结束，即不再有来自流的输入

EOF which expands to an integer constant expression, with type int and a negative value, that is returned by several functions to indicate end-of-file, that is, no more input from a stream

这不是您可以从文件中读取的值。 getc 是带外值，在文件结束以外的任何情况下都不会返回。

It's not a value that you can read from a file. It's an "out of band" value that getc and such can't return in any case other than "end of file".

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