Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
Practical – 01
AIM: - Program to implement Lexical Analyzer.
What is Lexical Analyzer?
A lexical analyzer, also known as a lexer or scanner.
It is a component of a compiler that processes input text (usually source code) and
converts it into a sequence of tokens.
Each token represents a basic element of the language, such as keywords, identifiers,
operators, and literals.
Source Code: -
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#define MAX 100
int isKeyword(char *str) {
const char *keywords[] = {
"int", "float", "if", "else", "while", "for", "return", "void", "main"
};
for (int i = 0; i < 9; i++) {
if (strcmp(str, keywords[i]) == 0) return 1;
}
return 0;
}
int isOperator(char c) {
char operators[] = "+-*/%=<>";
for (int i = 0; operators[i] != '\0'; i++) {
if (c == operators[i])
return 1;
}
return 0;
}
void lexicalAnalyzer(char *code) {
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
int i = 0;
char token[MAX];
printf("Tokens:\n");
while (code[i] != '\0') {
if (isspace(code[i])) {
i++;
continue;
}
if (isalpha(code[i])) {
int j = 0;
while (isalnum(code[i])) {
token[j++] = code[i++];
}
token[j] = '\0';
if (isKeyword(token)) printf("Keyword: %s\n", token);
else
printf("Identifier: %s\n", token);
}
else if (isdigit(code[i]))
{
int j = 0;
while (isdigit(code[i])) { token[j++] = code[i++];
}
token[j] = '\0';
printf("Number: %s\n", token);
}
else if (isOperator(code[i])) {
printf("Operator: %c\n", code[i]); i++;
}
else {
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
printf("Delimiter: %c\n", code[i]); i++;
}
}
}
int main() {
char code[MAX];
printf("Enter a code snippet: ");
fgets(code, MAX, stdin);
lexicalAnalyzer(code);
return 0;
}
OUTPUT: -
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
Practical – 02
AIM: - Program to count digits, vowels and symbols in C.
SOURCE CODE: -
#include <stdio.h>
#include <ctype.h>
int main() {
char str[100];
int digits = 0, vowels = 0, symbols = 0;
printf("Enter a string: ");
fgets(str, sizeof(str), stdin);
for (int i = 0; str[i] != '\0'; i++)
char ch = str[i];
if (isdigit(ch))
digits++;
else if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' || ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch
== 'U')
vowels++;
else if (!isalnum(ch) && !isspace(ch))
symbols++;
printf("Digits: %d\n", digits);
printf("Vowels: %d\n", vowels);
printf("Symbols: %d\n", symbols);
return 0;
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
OUTPUT: -
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
Practical – 03
AIM: - Program to check validation of User Name and Password in C.
SOURCE CODE: -
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define USERNAME_MIN_LENGTH 3
#define USERNAME_MAX_LENGTH 15
#define PASSWORD_MIN_LENGTH 8
int isValidUsername(const char *username) {
int length = strlen(username);
if (length < USERNAME_MIN_LENGTH || length > USERNAME_MAX_LENGTH) {
return 0;
if (isdigit(username[0])) {
return 0;
for (int i = 0; i < length; i++) {
if (!isalnum(username[i]) && username[i] != '_') {
return 0;
return 1;
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
int isValidPassword(const char *password) {
int length = strlen(password);
if (length < PASSWORD_MIN_LENGTH) {
return 0;
int hasUpper = 0, hasLower = 0, hasDigit = 0, hasSpecial = 0;
for (int i = 0; i < length; i++) {
if (isupper(password[i])) {
hasUpper = 1;
} else if (islower(password[i])) {
hasLower = 1;
} else if (isdigit(password[i])) {
hasDigit = 1;
} else if (ispunct(password[i])) {
hasSpecial = 1;
return hasUpper && hasLower && hasDigit && hasSpecial;
int main() {
char username[20];
char password[20];
printf("Enter username: ");
scanf("%s", username);
if (isValidUsername(username)) {
printf("Username is valid.\n");
} else {
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
printf("Invalid username. It must be 3-15 characters long, start with a letter, and can only contain letters,
digits, and underscores.\n");
return 1;
printf("Enter password: ");
scanf("%s", password);
if (isValidPassword(password)) {
printf("Password is valid.\n");
} else {
printf("Invalid password. It must be at least 8 characters long and contain at least one uppercase letter, one
lowercase letter, one digit, and one special character.\n");
return 1;
printf("Username and password are valid.\n");
return 0;
OUTPUT: -
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
Practical – 04
AIM: - Program to implement Predictive Parsing LL (1) in C.
Source Code: -
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAX 100
#define EMPTY "e" // For epsilon production
char table[10][10][MAX];
char nonTerminals[10];
char terminals[10];
int numNonTerminals = 0, numTerminals = 0;
char stack[MAX];
int top = -1;
void push(char *str) {
for (int i = strlen(str) - 1; i >= 0; i--) {
stack[++top] = str[i];
}
}
void pop() {
if (top >= 0) {
top--;
}
}
char peek() {
return top >= 0 ? stack[top] : '\0';
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
}
int getSymbolIndex(char *array, char symbol) {
for (int i = 0; i < strlen(array); i++) {
if (array[i] == symbol) {
return i;
}
}
return -1;
}
void displayStack() {
printf("Stack: ");
for (int i = 0; i <= top; i++) {
printf("%c", stack[i]);
}
printf("\n");
}
void predictiveParsing(char *input) {
int ptr = 0;
char currentSymbol; push("$");
push(&nonTerminals[0]); // Push the start symbol
printf("Parsing Steps:\n");
while (peek() != '$') {
currentSymbol = peek();
if (currentSymbol == input[ptr]) {
printf("Matched: %c\n", currentSymbol);
pop();
ptr++;
}
else if (strchr(nonTerminals, currentSymbol)) {
int ntIndex = getSymbolIndex(nonTerminals, currentSymbol);
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
int tIndex = getSymbolIndex(terminals, input[ptr]);
if (tIndex == -1) {
printf("Error: Unexpected symbol '%c'\n", input[ptr]); return;
}
char *production = table[ntIndex][tIndex];
if (strcmp(production, "") == 0) {
printf("Error: No rule for '%c' with '%c'\n", currentSymbol, input[ptr]);
return;
}
printf("Production: %c -> %s\n", currentSymbol, production);
pop();
if (strcmp(production, EMPTY) != 0) {
push(production);
}
}
else {
printf("Error: Unexpected symbol '%c'\n", currentSymbol);
return;
}
displayStack(); // Optional: For debugging purposes
}
if (input[ptr] == '$') {
printf("Input accepted.\n");
}
else {
printf("Error: Input not fully consumed.\n");
}
}
int main() {
int i, j;
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
char input[MAX];
printf("Enter number of non-terminals: ");
scanf("%d", &numNonTerminals);
printf("Enter non-terminals (single character each): ");
for (i = 0; i < numNonTerminals; i++) {
scanf(" %c", &nonTerminals[i]);
}
printf("Enter number of terminals: ");
scanf("%d", &numTerminals);
printf("Enter terminals (single character each): ");
for (i = 0; i < numTerminals; i++) {
scanf(" %c", &terminals[i]);
}
terminals[numTerminals++] = '$';
for (i = 0; i < numNonTerminals; i++) {
for (j = 0; j < numTerminals; j++) {
strcpy(table[i][j], "");
}
}
printf("Enter parsing table (use e for epsilon):\n");
for (i = 0; i < numNonTerminals; i++) {
for (j = 0; j < numTerminals; j++) {
printf("Production for %c with %c: ", nonTerminals[i], terminals[j]); scanf("%s",
table[i][j]);
}
}
printf("Enter the input string (end with $): ");
scanf("%s", input);
predictiveParsing(input);
return 0;
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
OUTPUT: -
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
Practical – 05
AIM: -Program to implement Recursive Descent Parsing in C.
Source Code: -
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAX 100
char input[MAX];
int pos = 0;
void E();
void T();
void E_prime();
void T_prime();
void F();
void error() {
printf("Error in parsing!\n");
exit(1);
}
void match(char expected) {
if (input[pos] == expected) {
printf("Matched: %c\n", input[pos]);
pos++;
} else {
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
error();
}
}
void E() {
printf("Applying Production: E -> T E'\n");
T();
E_prime();
}
void E_prime() {
if (input[pos] == '+') {
printf("Applying Production: E' -> + T E'\n");
match('+');
T();
E_prime();
} else {
printf("Applying Production: E' -> epsilon\n");
}
}
void T() {
printf("Applying Production: T -> F T'\n");
F();
T_prime();
}
void T_prime() {
if (input[pos] == '*') {
printf("Applying Production: T' -> * F T'\n");
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
match('*');
F();
T_prime();
} else {
printf("Applying Production: T' -> epsilon\n");
}
}
void F() {
if (isalnum(input[pos])) {
printf("Applying Production: F -> id\n");
match(input[pos]);
} else if (input[pos] == '(') {
printf("Applying Production: F -> ( E )\n");
match('(');
E();
match(')');
} else {
error();
}
}
int main() {
printf("Enter the input string (end with $): ");
scanf("%s", input);
if (input[strlen(input) - 1] != '$') {
printf("Error: Input string must end with '$'.\n");
return 1;
}
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
Faculty of Engineering & Technology
Subject: - Complier Design (303105350)
B. Tech AI & AI-DS 6th Semester
printf("Parsing Steps:\n");
E();
if (input[pos] == '$') {
printf("Input accepted.\n");
} else {
printf("Parsing failed! Extra characters found.\n");
}
return 0;
}
OUTPUT: -
Name: - Smita Singh
Enrollment: - 2203031241233 Page |
Division: - 6AI9
