diff --git a/cclox_src/scanner.cc b/cclox_src/scanner.cc
index dbc0a1d..2bd0668 100644
--- a/cclox_src/scanner.cc
+++ b/cclox_src/scanner.cc
@@ -2,10 +2,32 @@
 #include "token.hh"
 #include "error_handler.hh"
 #include "object.hh"
+#include <string>
 #include <vector>
 
 extern ErrorHandler error_handler;
 
+Scanner::Scanner(const std::string &code) : code{code}, tokens{}, start{0}, current{0}, line{1} {
+  keywords = {
+    std::pair<std::string, TokenType>("and", TokenType::AND),
+    std::pair<std::string, TokenType>("class", TokenType::CLASS),
+    std::pair<std::string, TokenType>("else", TokenType::ELSE),
+    std::pair<std::string, TokenType>("false", TokenType::FALSE),
+    std::pair<std::string, TokenType>("for", TokenType::FOR),
+    std::pair<std::string, TokenType>("fun", TokenType::FUN),
+    std::pair<std::string, TokenType>("if", TokenType::IF),
+    std::pair<std::string, TokenType>("nil", TokenType::NIL),
+    std::pair<std::string, TokenType>("or", TokenType::OR),
+    std::pair<std::string, TokenType>("print", TokenType::PRINT),
+    std::pair<std::string, TokenType>("return", TokenType::RETURN),
+    std::pair<std::string, TokenType>("super", TokenType::SUPER),
+    std::pair<std::string, TokenType>("this", TokenType::THIS),
+    std::pair<std::string, TokenType>("true", TokenType::TRUE),
+    std::pair<std::string, TokenType>("var", TokenType::VAR),
+    std::pair<std::string, TokenType>("while", TokenType::WHILE),
+  };
+}
+
 std::vector<Token> Scanner::scan_tokens() {
   while (!is_at_end()) {
     start = current;
@@ -20,6 +42,18 @@ bool Scanner::is_at_end() {
   return current >= code.size();
 }
 
+bool Scanner::is_digit(char c) {
+  return c >= '0' && c <= '9';
+}
+
+bool Scanner::is_alpha(char c) {
+  return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_';
+}
+
+bool Scanner::is_alphanumeric(char c) {
+  return is_alpha(c) || is_digit(c);
+}
+
 void Scanner::scan_token() {
   char c = advance();
   switch (c) {
@@ -66,7 +100,14 @@ void Scanner::scan_token() {
       string();
       break;
     default:
-      error_handler.error(line, "Unexpected character.");
+      if (is_digit(c)) {
+        number();
+      } else if(is_alpha(c)) {
+        identifier();
+      } else {
+        error_handler.error(line, "Unexpected character.");
+      }
+
       break;
   }
 }
@@ -92,6 +133,14 @@ char Scanner::peek() {
   return code.at(current);
 }
 
+char Scanner::peek_next() {
+  if (current + 1 >= code.size()) {
+    return '\0';
+  }
+
+  return code.at(current + 1);
+}
+
 void Scanner::add_token(TokenType type) {
   add_token(type, Object{});
 }
@@ -121,3 +170,36 @@ void Scanner::string() {
   std::string value = code.substr(no_quote_start, no_quote_end - no_quote_start);
   add_token(TokenType::STRING, Object(StringObjectType::LITERAL, value));
 }
+
+void Scanner::number() {
+  while (is_digit(peek())) {
+    advance();
+  }
+
+  if (peek() == '.' && is_digit(peek_next())) {
+    // Consume the "."
+    advance();
+
+    while (is_digit(peek())) {
+      advance();
+    }
+  }
+
+  std::string value = code.substr(start, current - start);
+  add_token(TokenType::NUMBER, Object(std::stod(value)));
+}
+
+void Scanner::identifier() {
+  while (is_alphanumeric(peek())) {
+    advance();
+  }
+
+  std::string value = code.substr(start, current - start);
+  auto it = keywords.find(value);
+  if (it != keywords.end()) {
+    TokenType type = it->second;
+    add_token(type);
+  } else {
+    add_token(TokenType::IDENTIFIER, Object(StringObjectType::IDENTIFIER, value));
+  }
+}
diff --git a/cclox_src/scanner.hh b/cclox_src/scanner.hh
index fb9b0e2..e819094 100644
--- a/cclox_src/scanner.hh
+++ b/cclox_src/scanner.hh
@@ -3,20 +3,29 @@
 #include "token.hh"
 #include <cstddef>
 #include <vector>
+#include <string>
+#include <unordered_map>
 
 struct Scanner {
-  Scanner(const std::string &code) : code{code}, tokens{}, start{0}, current{0}, line{1} {};
+  Scanner(const std::string &code);
   std::vector<Token> scan_tokens();
   bool is_at_end();
+  bool is_digit(char c);
+  bool is_alpha(char c);
+  bool is_alphanumeric(char c);
   void scan_token();
   char advance();
   bool match(char expected);
   char peek();
+  char peek_next();
   void add_token(TokenType type);
   void add_token(TokenType type, Object literal);
   void string();
+  void number();
+  void identifier();
 
   std::string code;
   std::vector<Token> tokens;
   std::size_t start, current, line;
+  std::unordered_map<std::string, TokenType> keywords;
 };