C Program to Design Lexical Analyzer

Written by siddhartha. Posted in Compiler Design

Source Code

/*************************************************************************************/
/*  C Program to Design Lexical Analyzer*/
/*  Download more programs at http://sourcecode4u.com/ */
/*************************************************************************************/
#include<string.h>
#include<ctype.h>
#include<stdio.h>
void keyword(char str[10])
{ if(strcmp("for",str)==0||strcmp("while",str)==0||strcmp("do",str)==0||
    strcmp("int",str)==0||strcmp("float",str)==0||strcmp("char",str)==0||
    strcmp("double",str)==0||strcmp("static",str)==0||strcmp("switch",str)==0||
    strcmp("case",str)==0)
    printf("\n%s is a keyword",str);
    else
    printf("\n%s is an identifier",str);
}
main()
{
    FILE *f1,*f2,*f3;
    char c,str[10],st1[10];
    int num[100],lineno=0,tokenvalue=0,i=0,j=0,k=0;
    printf("\nEnter the c program");/*gets(st1);*/
    f1=fopen("input","w");
    while((c=getchar())!=EOF)
    putc(c,f1);
    fclose(f1);
    f1=fopen("input","r");
    f2=fopen("identifier","w");
    f3=fopen("specialchar","w");
    while((c=getc(f1))!=EOF)
    {
        if(isdigit(c))
        {
            tokenvalue=c-'0';
            c=getc(f1);
            while(isdigit(c))
            {
                tokenvalue*=10+c-'0';
                c=getc(f1);
            }
            num[i++]=tokenvalue;
            ungetc(c,f1);
        } else if(isalpha(c))
        {
            putc(c,f2);
            c=getc(f1);
            while(isdigit(c)||isalpha(c)||c=='_'||c=='$')
            {
                putc(c,f2);
                c=getc(f1);
            }
            putc(' ',f2);
            ungetc(c,f1);
        } else if(c==' '||c=='\t')
        printf(" ");
        else if(c=='\n')
        lineno++;
        else
        putc(c,f3);
    }
    fclose(f2);
    fclose(f3);
    fclose(f1);
    printf("\nThe no's in the program are");
    for(j=0;j<i;j++)
    printf("%d",num[j]);
    printf("\n");
    f2=fopen("identifier","r");
    k=0;
    printf("The keywords and identifiersare:");
    while((c=getc(f2))!=EOF)
    {
        if(c!=' ')
        str[k++]=c;
        else
        {
            str[k]='\0';
            keyword(str);
            k=0;
        }
    }
    fclose(f2);
    f3=fopen("specialchar","r");
    printf("\nSpecial characters are");
    while((c=getc(f3))!=EOF)
    printf("%c",c);
    printf("\n");
    fclose(f3);
    printf("Total no. of lines are:%d",lineno);
}

Out Put

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