Lexical Analyzer in C and C++

Here you will get the program to actualize lexical analyzer in C and C++.

The compiler is liable for changing over significant level language in machine language. There are a few stages associated with this and the lexical investigation is the main stage.

Lexical analyzer peruses the characters from source code and converts it into tokens.

Various tokens or lexemes are:

Watchwords

Identifiers

Administrators

Constants

Take beneath model.

c = a + b;

Presently beneath I have given execution of basic lexical analyzer which peruses source code from the record and afterwards creates tokens.

Program for Lexical Analyzer in C

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
 
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[] = "+-*/%=";
	FILE *fp;
	int i,j=0;
	
	fp = fopen("program.txt","r");
	
	if(fp == NULL){
		printf("error while opening the file\n");
		exit(0);
	}
	
	while((ch = fgetc(fp)) != EOF){
   		for(i = 0; i < 6; ++i){
   			if(ch == operators[i])
   				printf("%c is operator\n", ch);
   		}
   		
   		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 indentifier\n", buffer);
   		}
   		
	}
	
	fclose(fp);
	
	return 0;
}

The source code present in record appears in the above picture.

Program for Lexical Analyzer in C++

#include<iostream>
#include<fstream>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
 
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("program.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<<ch<<" is operator\n";
   		}
   		
   		if(isalnum(ch)){
   			buffer[j++] = ch;
   		}
   		else if((ch == ' ' || ch == '\n') && (j != 0)){
   				buffer[j] = '\0';
   				j = 0;
   				   				
   				if(isKeyword(buffer) == 1)
   					cout<<buffer<<" is keyword\n";
   				else
   					cout<<buffer<<" is indentifier\n";
   		}
   		
	}
	
	fin.close();
	
	return 0;
}

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Output