Lexical Analyzer

Program : Lexical Analyzer

#include<stdio.h>

#include<conio.h>

#include<stdlib.h>

void main() //main function

{

FILE *p;

int i=0,j=0,k=0,flag;

char x,temp[100];

char digit[10]={'0','1','2','3','4','5','6','7','8','9'};



char key[25][10]={"auto","break","case","char","const","continue",

"default","do","double","else","enum","for",

"goto","if","int","return","signed","static",

"struct","union","while","switch","void","float"};

char opera[10][17]={"+","=","*","/","-",">","<"};

clrscr();

p=fopen("text.txt","r"); //open file

if(p==NULL) //if file not present

printf("cannot open the file");

else

{

printf("\tKEYWORD\tIDENTIFIER\tOPERATOR\n");

while((x=fgetc(p))!=EOF)

{

if((x!=' ')&&(x!='\t')&&(x!='\n')) //get keyword

{

temp[i]=x;

i++;

temp[i]='\0';

}

else

{

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

temp[j]=' ';

i=0;

}

for(k=0;k<25;k++) //compare with key

{

if(strcmp(temp,key[k])==0)

{

printf("\n\t%s",temp);

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

temp[j]=' ';

i=0;

}

}

for(j=0;j<strlen(temp);j++) //check identifiers

{

for(k=0;k<11;k++)

{

flag=0;

if(temp[j]==digit[k])

{

flag=1;

break;

}

}

}

if(flag!=0)

{

printf("\n\t\t%s",temp);

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

temp[j]=' ';

i=0;

}

for(k=0;k<10;k++) //check if operator

{

if(strcmp(temp,opera[k])==0)

{

printf("\n\t\t\t\t%s",temp);

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

temp[j]=' ';

i=0;

}

}

}

}

fclose(p); //close the file

getch();

}