lexical analyser program

#include <stdio.h>

#include <string.h>

#include <ctype.h>

// Check if token is a keyword

int isKeyword(char *word) {

char *keywords[] = {"int", "float", "if", "else", "while", "for", "return"};

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

if (strcmp(word, keywords[i]) == 0)

return 1;

}

return 0;

}

// Check if token is a valid identifier

int isIdentifier(char *word) {

if (!(isalpha(word[0]) || word[0] == '_'))

return 0;

for (int i = 1; word[i] != '\0'; i++) {

if (!(isalnum(word[i]) || word[i] == '_'))

return 0;

}

return 1;

}

// Check if token is a number (literal)

int isNumber(char *word) {

for (int i = 0; word[i] != '\0'; i++) {

if (!isdigit(word[i]))

return 0;

}

return 1;

}

// Check if character is an operator

int isOperator(char ch) {

return (ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == '=');

}

// Check if character is punctuation

int isPunctuation(char ch) {

return (ch == ',' || ch == ';' || ch == '(' || ch == ')' || ch == '{' || ch == '}');

}

int main() {

FILE *fp;

char filename[100], ch, word[100];

int i = 0;

printf("Enter file name: ");

scanf("%s", filename);

fp = fopen(filename, "r");

if (fp == NULL) {

printf("Error: File not found.\n");

return 1;

}

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

if (isalnum(ch) || ch == '_') {

word[i++] = ch;

} else {

word[i] = '\0';

i = 0;

if (strlen(word) > 0) {

if (isKeyword(word))

printf("Keyword: %s\n", word);

else if (isNumber(word))

printf("Literal: %s\n", word);

else if (isIdentifier(word))

printf("Identifier: %s\n", word);

else

printf("Unknown token: %s\n", word);

}

if (isOperator(ch))

printf("Operator: %c\n", ch);

else if (isPunctuation(ch))

printf("Punctuation: %c\n", ch);

}

}

fclose(fp);

return 0;

}