实验报告一一、 实验目的编制一个词法分析程序。二、 实验内容和要求输入：源程序字符串。输出：二元组（种别，单词符号本身）。三、 实验方法、步骤及结果测试2.主要程序段及其解释：for(i=0;ch[i]!='\0';i++){if((ch[i]=='+')||(ch[i]=='=')||(ch[i]=='/')||(ch[i]=='*')||(ch[i]=='>=')||(ch[i]=='<=')||(ch[i]=='<')||(ch[i]=='>'))//判断字符是否为运算符；switch(ch[i]){case '+':printf("(2,%c)",ch[i]);printf("\n");break;case '-':printf("(3,%c)",ch[i]);printf("\n");break;case '*':printf("(4,%c)",ch[i]);printf("\n");break;case'/':printf("(5,%c)",ch[i]);printf("\n");break;                  case '<':printf("(6,%c)",ch[i]);printf("\n");break;case '<=':printf("(7,%c)",ch[i]);printf("\n");break;case'>':printf("(8,%c)",ch[i]);printf("\n");break;                     case '>=':printf("(9,%c)",ch[i]);printf("\n");break;case '=':printf("(11,%c)",ch[i]);printf("\n");break;default:break;}else if((ch[i]>=32)&&(ch[i]<=41)||(ch[i]=='.')||(ch[i]>=91&&ch[i]<=96)||(ch[i]==';')||(ch[i]=='?'))//判断字符是否为界符；switch(ch[i]){case '#':printf("(0,%c)",ch[i]);printf("\n");break;case ';':printf("(12,%c)",ch[i]);printf("\n");break;case '(':printf("(13,%c)",ch[i]);printf("\n");break;case ')':printf("(14,%c)",ch[i]);printf("\n");break;case '?':printf("(15,%c)",ch[i]);printf("\n");break;case '.':printf("(16,%c)",ch[i]);printf("\n");break;case ' ':printf("(17,%c)",ch[i]);printf("\n");break;case '"':printf("(18,%c)",ch[i]);printf("\n");break;case ',':printf("(19,%c)",ch[i]);printf("\n");break;default:printf("(35,%c)",ch[i]);printf("\n");break;}else  if(ch[i]>=48&&ch[i]<=57)//判断字符是否为常数；
{printf("(20,");//常数的种别码为28；for(;(ch[i]>=48&&ch[i]<=57);i++){printf("%c",ch[i]);//printf("%c",a[k]);
}i--;printf(")\n");}//memset(a,0,100);k=0;}else{if((ch[i]>='a'&&ch[i]<='z')||(ch[i]>='A'&&ch[i]<='Z'))for(;((ch[i]>='a'&&ch[i]<='z')||(ch[i]>='A'&&ch[i]<='Z'));i++,j++){str[j]=ch[i];//把一整串字符赋值给str数组}i--;if(strcmp(str,"auto")==0|strcmp(str,"int")==0||strcmp(str,"do")==0||strcmp(str,"while")==0||            strcmp(str,"long")==0||strcmp(str,"short")==0||strcmp(str,"case")==0||(str,"switch")==0||        strcmp(str,"typedef")==0||(str,"const")==0||(str,"static")==0||strcmp(str,"double")==0||strcmp(str,"char")==0||(str,"return")==0)//判断字符是否为关键字
{printf("(1,%s)\n",str);memset(str,0,100); j=0;}else{//printf("(29,%s)\n",str);
printf("(10,%s)\n",str);memset(str,0,100); j=0;}}}}3.运行结果及分析四、 实验总结问题：不知道如何把关键字作为一个整体输出；解决方法：先把单个字符存在一个字符数组里，然后判断是否为关键字，如果是的话，用%s把字符数组里的字符输出；否则的为标识符。体会：通过在编程中不断的发现问题，然后不断的解决，使自己更加熟练的掌握编程的思想。