C复习笔记(2)-6.18

6月18日

#include <stdio.h>

(1)

/*count characters in input; 1st version*/

int main(void)

{

    long nc;

    nc = 0;

    while (getchar() != EOF)

       ++nc;

    printf("%ld/n",nc);

    return 0;

}

Note: when you Enter Backspace key, the machine would send the buffered string into input,

So 12345 counts 6.

 

(2)

#include <stdio.h>

 

/*count lines in input;*/

int main(void)

{

    int c,nl;

   

    nl = 0;

    while ((c = getchar())!= EOF)

       if (c == '/n')

           ++nl;

    printf("%ld",nl);

}

Newcomers to C occasionally write = when they mean ==. The result is usually a legal expression, so you will get no warning.

 

A character written between single quotes represents an integer value equal to the numerical value of the character in the machine's character set. This is called a character constant, although it is just another way to write a small integer. So, for example, 'A' is a character constant; in the ASCII character set its value is 65, the internal representation of the character A.

 

You should note carefully that '/n' is a single character, and in expressions is just an integer; on the other hand, “/n” is a string constant that happens to contain only one character.