Question

PLEASE COMMENT THE FOLLOWING LEXICAL ANALYSER PROGRAM. Thank you.

#include

#include

#include

#include

#include

using namespace std;

int isKeyword(char buffer[]){

char keywords[32][10] = {"auto","break","case","char","const","continue","default",

"do","double","else","enum","extern","float","for","goto",

"if","int","long","register","return","short","signed",

"sizeof","static","struct","switch","typedef","union",

"unsigned","void","volatile","while"};

int i, flag = 0;

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

if(strcmp(keywords[i], buffer) == 0){

flag = 1;

break;

}

}

return flag;

}

int main(){

char ch, buffer[15], operators[] = "+-*/%=";

ifstream fin("Text.txt");

int i,j=0;

if(!fin.is_open()){

cout<<"error while opening the file\n";

exit(0);

}

while(!fin.eof()){

ch = fin.get();

  

for(i = 0; i < 6; ++i){

if(ch == operators[i])

cout<

}

  

if(isalnum(ch)){

buffer[j++] = ch;

}

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

buffer[j] = '\0';

j = 0;

if(isKeyword(buffer) == 1)

cout<

else

cout<

}

}

fin.close();

return 0;

}

Answer 1

Working code implemented in C and appropriate comments provided for better understanding.

Source Code for main.c:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>

int isKeyword(char buffer[]){
char keywords[35][30] = {"auto","break","case","char","const","continue","default",
"do","double","else","enum","extern","float","for","goto",
"if","int","long","register","return","short","signed",
"sizeof","static","struct","switch","typedef","union",
"unsigned","void","volatile","while","main","includestdioh","stdio"};
int i, flag = 0;

for(i = 0; i < 35; ++i){
if(strcmp(keywords[i], buffer) == 0){
flag = 1;
break;
}
}

return flag;
}

int main(){
char ch, buffer[15], operators[] = "+-*/%=";
FILE *fp;
int i,j=0;

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

if(fp == NULL){
printf("error while opening the file\n");
// <stdlib.h> is used for exit
exit(0);
}

while((ch = fgetc(fp)) != EOF){
for(i = 0; i < 6; ++i){
if(ch == operators[i])
printf("%c is operator\n", ch);
}

// isalnum need ctype library import
if(isalnum(ch)){
buffer[j++] = ch;
}
  
else if((ch == ' ' || ch == '\n') && (j != 0)){
buffer[j] = '\0';
j = 0;

if(isKeyword(buffer) == 1)
printf("%s is keyword\n", buffer);
else
printf("%s is identifier\n", buffer);
}

}

fclose(fp);

return 0;
}

Sample Output Screenshots: