Why is type int needed to handle EOF and return of getchar()?

问题

As written in book-

The problem is distinguishing the end of the input from valid data. The solution is that getchar returns a distinctive value when there is no more input, a value that cannot be confused with any real character. This value is called EOF,for "end of file." We must declare c to be a type big enough to hold any value that getchar returns. We can't use char since c must be big enough to hold EOF in addition to any possible char. Therefore we use int.

main()
{
    int c;
    c = getchar();
    while(c != EOF) {
    putchar(c);
    c = getchar();
    }
}

I am not able to understand the actual reason of using int instead of char. What will be returned by EOF such that cannot be stored in char.

回答1:

A char can hold 256 different values (0 to 255). If EOF was a char, the value of EOF would therefore be some value between 0 and 255, which would imply that there would be one character that you cannot read. Therefore the value of EOF cannot be between 0 and 255, which implies that it cannot fit into a char, which implies that its type must be larger than char, for example an int.

In other words EOF is not a char and we don't want to store it in a char. It's only purpose is to enable a program to detect that one char beyond the end of the file has been attempted to read.

Or still in other words: let's suppose EOF is defined as 255 and therefore fit's into a char. Now let's suppose getchar returns the value 255 (that is EOF). Now what does that value represent? Is it an EOF or is it the character 255?

来源：https://stackoverflow.com/questions/48870708/why-is-type-int-needed-to-handle-eof-and-return-of-getchar

标签

getchar