#include<stdio.h>#include<stdlib.h>#include<string.h>#define _KEY_WOED_END "waiting for your expanding"     //关键字结束标志 typedef struct{    int typenum;    char * word;}WORD; char input[255];   //输入换缓冲区 char token[255]="";   //单词缓冲区 int p_input;        //输入换缓冲区指针 int p_token;        //单词缓冲区指针 char ch;           //当前所读的字符 char *rwtab[]={"begin","if","then","while","do","end",_KEY_WOED_END};        //C语言关键字 WORD * scaner();    //词法扫描函数，获得关键字 main(){    int over=1;    WORD *oneword;    oneword=(WORD *)malloc(sizeof(WORD));    printf("请输入您的字符串（以#作为结束标志）:");    scanf("%[^#]s",input);                        //读入源程序字符串到缓冲区，以#结束，允许多行输入    p_input=0;    printf("您输入的字符串是:%s\n\n",input);    while(over<1000&&over!=-1)    {        oneword=scaner();        printf("(%d,%s)\n",oneword->typenum,oneword->word);        over=oneword->typenum;    }    printf("\n\n备注:数字10代表所输入的不是关键词，只是普通词\n");    printf("     数字20代表您输入的是数字\n");    printf("     数字1000是结束标志\n\n"); } //需要用到的自编函数参考实现//从输入缓冲区读取一个字符到ch中 char m_getch(){    ch=input[p_input];    p_input=p_input+1;    return (ch);}   //去掉空白字符void getbc(){    while(ch==‘ ‘||ch==10){    ch=input[p_input];    p_input=p_input+1;    }} //拼接单词void concat(){    token[p_token]=ch;    p_token=p_token+1;    token[p_token]=‘\0‘;}   //判断是否字母int letter(){    if(ch>=‘a‘&&ch<=‘z‘||ch>=‘A‘&&ch<=‘Z‘)return 1;    else return 0;} //判断是否数字int digit(){    if(ch>=‘0‘&&ch<=‘9‘)        return 1;    else        return 0;} //检索关键字表格int reserve(){    int i=0;    for(i=0;i<7;i++)    {        if(!strcmp(rwtab[i],token))        {            return i+1;        }        i=i+1;    }    return 10;}    //回退一个字符void retract(){    p_input=p_input-1;} WORD *scaner(){    WORD *myword;    myword=(WORD *)malloc(sizeof(WORD));    myword->typenum=10;    myword->word="";    p_token=0;    m_getch();    getbc();    if(letter())    {        while(letter()||digit())        {           concat();           m_getch();                 }        retract();        myword->typenum=reserve();        myword->word=token;        return(myword);    }    else if(digit())    {        while(digit())        {            concat();            m_getch();        }        retract();        myword->typenum=20;        myword->word=token;        return(myword);    }    else    {        switch(ch)        {        case ‘=‘:m_getch();            if(ch==‘=‘)            {                myword->typenum=39;                myword->word="==";                return(myword);            }            retract();            myword->typenum=21;            myword->word="=";            return(myword);            break;        case ‘+‘:            myword->typenum=22;                myword->word="+";                return(myword);                break;        case ‘-‘:            myword->typenum=23;                myword->word="-";                return(myword);                break;        case ‘*‘:            myword->typenum=24;            myword->word="*";            return(myword);            break;        case ‘/‘:            myword->typenum=25;            myword->word="/";            return(myword);            break;        case ‘(‘:            myword->typenum=26;            myword->word="(";            return(myword);            break;        case ‘)‘:            myword->typenum=27;            myword->word=")";            return(myword);            break;        case ‘[‘:            myword->typenum=28;            myword->word="[";            return(myword);            break;        case ‘]‘:            myword->typenum=29;            myword->word="]";            return(myword);            break;        case ‘{‘:            myword->typenum=30;            myword->word="{";            return(myword);            break;        case ‘}‘:            myword->typenum=31;            myword->word="}";            return(myword);            break;        case ‘,‘:            myword->typenum=32;            myword->word=",";            return(myword);            break;        case ‘:‘:            myword->typenum=33;            myword->word=":";            return(myword);            break;        case ‘;‘:            myword->typenum=34;            myword->word=";";            return(myword);            break;        case ‘>‘:            myword->typenum=35;            myword->word=">";            return(myword);            break;        case ‘<‘:            myword->typenum=36;            myword->word="<";            return(myword);            break;        case ‘!‘:            m_getch();            if(ch==‘=‘)            {                myword->typenum=40;                myword->word="!=";                return(myword);            }            retract();            myword->typenum=-1;            myword->word="ERROR";            return(myword);            break;        case ‘\0‘:            myword->typenum=1000;            myword->word="OVER";            return(myword);            break;        default:            myword->typenum=-1;            myword->word="ERROR";            return(myword);            }        }    }