SP Practical 1

Practical : 1
Subject : System Programming

Aim : Write C++ program to implement the lexical analyzer.

Source Code :

#include<stdio.h>

#include<conio.h>

#include<string.h>

#include<ctype.h>

char keyword[32][10]={"void","int","char","float","signed","unsigned","long","double","enum","auto","register","return","struct","break","case","const","continue","default","do","else","extern","for","goto","if","short","sizeof","static","switch","typedef","union","volatile","while"};

char op[7]={"+->*/!="};

void main()

{

            int i,j=0,flag=0;

            char ch;

            char str[20];

            FILE *fp;

            fp=fopen("file38.txt","r");

            if(fp==NULL)

            {

                        printf("there is no content in file");

                        exit(0);

            while((ch=fgetc(fp))!=EOF)

            {

                        flag=0;

                        for(i=0;i<7;i++)

                        {

                                    if(op[i]==ch)

                                    {

                                                flag=1;

                                    }

                        }

                        if(flag==1)

                        {

                                    printf("%c is operator \n",ch);

                        }

                        else if(ch==';')

                        {

                                    printf("statement is over\n");

                                    break;

                        }

                        else if((ch==' ' || ch=='\n') && j!=0)

                        {

                                    str[j]='\0';

                                    j=0;

                                    for(i=0;i<32;i++)

                                    {

                                                if(strcmp(keyword[i],str)==0)

                                                {

                                                            flag=1;

                                                }

                                     }

                                     if(flag==1)

                                     {

                                                printf("%s is keyword\n",str);

                                     }

                                     else

                                     {

                                                printf("%s is identifier\n",str);

                                     }

                                     while(str[j]!=NULL)

                                     {

                                                str[j]='\0';

                                     }

                        }

                        else if(isdigit(ch))

                        {

                                    printf("%c is a constant\n",ch);

                        }

                        else

                        {

                                    str[j]=ch;

                                    j++;

                        }

            }

            fclose(fp);

}

Output :