The C Programming Language 1-9 — Windows Live

我用了位置标识的方法，虽然有点臃肿，不过道理还是很明显的

#include <stdio.h>

#define WAIT 0   //an initial place
#define FIRST 1  //a place in the first blank
#define OTHER 2  //a place in the balnk that follows
#define WORD 3   //a place in a word
#define FIRST_OVER 4

main()
{
    long state,c;
    state = WAIT;
    c = getchar();
    while (c != EOF)
    {
    //make state into different value
        if ((state == WAIT) && (c == ‘ ‘)){
                state = FIRST;
                }
        if ((state == FIRST_OVER) && (c == ‘ ‘)){
                state = OTHER;
                }
        if ((state == OTHER) && (c != ‘ ‘)){
                state = WORD;
                }
        if ((state == WAIT) && (c != ‘ ‘)){
                state = WORD;
                }
     //process the character string by different value of state          
        if (state == FIRST){
                putchar(c);
                state = FIRST_OVER;
                }
        if (state == WORD){
                putchar(c);
                state = WAIT;
                }
        c = getchar();
    }
    system("pause");
}

Nothing is odd with the program here but if you don’t take care of two points here,you may get puzzled with the output display.

//1.5.2 character counting

#include <stdio.h>
main()
{
    long cn;
    cn = 0;
    while (getchar() != EOF){
        ++cn;
        }
    printf("%1d\n",cn);
    system("pause");
}

 
I can’t get the result at first,for that time,I directly enter a string with an ENTER,but find nothing given,that is,it don’t seem to work properly but the code is properly written,what’s wrong?
Asking a friends,I get the result,there’s nothing wrong with the code,but something not properly with the output.Check with the DOS blank like this:
type in a string that you want to test,and then turn to a new line type in ctrl and z,at last you will get a properly displayed answer.

ctrl+Z在控制台中就是EOF，输入的字符串末尾没有EOF，所以while循环会无限执行下去，以致无法执行printf部分，所以在控制台中输入zrtl+Z，给定一个EOF使得输入的string有这个结束符，就能跳到下一个printf了

Get inputs from related service,like keyboard,and then copy what you get to the output,like screen.

/*1.5.1 file copying – original version*/

#include <stdio.h>
main()
{
    int c = 0;
    c = getchar();
    while (c != EOF)
    {
        putchar(c);
        c = getchar();
    }
}

There’s something interesting here,we’ve learned printf() before,if we use it here,what will happen?

/*1.5.1 file copying*/

#include <stdio.h>
main()
{
    int c = 0;
    c = getchar();
    while (c != EOF)
    {
        c = getchar();
        printf("%d\n",c);
    }
}

The output of this program display input characters’ ASCII code instead of its original value and this is something different from putchar().
But I still have a question about it.It works alright but I’m afraid at the first input,it will return something,as far as I’m concerned,not properly designed.
If I type in one character,’1’ or ‘a’ for example,it will eventually give me a ‘10’,which,in the ASCII code,stands for Null;

and if I type in a string,’abcdef’ for instance,it will feedback every character’s ASCII code properly but lacks the last one’s own ASCII code instead of 10,which stands for a Null character;

if I type in nothing but only give an ‘Enter’,it will feedback nothing at all.
 
All the phenomenon above only exist at the first typing in,while at the next that follow,it will feedback properly.
As far as I am concerned,every character,no matter one character or a string,is terminated with a ‘’ whose ASCII code  is 10,but why the program fail to give input’s own ASCII code instead of only showing a ‘’\o’ ‘s?

用printf()替代putchar()之后，运行程序出现了一个比较有趣的问题。
第一次出入的字符总会得到错误的结果：如果输入单个字符，则只会返回10，而10在ASCII码中代表的是空位符；如果输入一个字符串，则字符串中最后一位字符的ASCII码无法得到，取而代之的还是一个10；如果什么也不输入，而只回车的话，就会什么也不得到。
然而上面这些现象在第二次输入时就不再出现了，所有的输入都得到想要的结果，当然，第二次输入回车还是会返回一个10.

现在我所掌握掌握的知识是，一个字符串，无论是单个字符还是一连串的字符，都是以结尾的，所以上面显示的10正是这个字符，可是为什么第一次输入的时候会出现错误呢？