diff --git a/cclox_src/main.cc b/cclox_src/main.cc
index 9c73496..e2694f5 100644
--- a/cclox_src/main.cc
+++ b/cclox_src/main.cc
@@ -1,6 +1,75 @@
-#include <cstdio>
+#include "token.hh"
+#include "scanner.hh"
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <sysexits.h>
+#include <cstdint>
+#include <vector>
+
+#define PROMPT "> "
+
+static bool had_error = false;
+
+void run_file(const char *path);
+void run_prompt();
+void run(const std::string &code);
+void error(int line, const std::string &message);
+void report(int line, const std::string &where, const std::string &message);
+
+int main(int argc, char *argv[]) {
+  if (argc > 2) {
+    std::cout << "Usage: cclox [script]\n";
+    exit(EX_USAGE);
+  }
+
+  if (argc == 2) {
+    run_file(argv[1]);
+  } else {
+    run_prompt();
+  }
 
-int main() {
-  printf("Hello from cclox\n");
   return 0;
 }
+
+void run_file(const char *path) {
+  if (std::ifstream source_code{path, std::ios::ate}) {
+    uint64_t size = source_code.tellg();
+    std::string code(size, '\0');
+    source_code.seekg(0);
+    source_code.read(&code[0], size);
+
+    run(code);
+    if (had_error) {
+      exit(EX_DATAERR);
+    }
+  }
+}
+
+void run_prompt() {
+  std::string line{};
+  std::cout << PROMPT;
+  while (std::getline(std::cin, line)) {
+    run(line);
+    std::cout << PROMPT;
+    had_error = false;
+  }
+}
+
+void run(const std::string &code) {
+  Scanner scanner{code};
+  std::vector<Token> tokens = scanner.scan_tokens();
+
+  for (auto token : tokens) {
+    std::cout << token << '\n';
+  }
+}
+
+void error(int line, const std::string &message) {
+  report(line, "", message);
+}
+
+void report(int line, const std::string &where, const std::string &message) {
+  std::cout << "[line " << line << "] Error" << where << ": " << message << '\n';
+  had_error = true;
+}
diff --git a/cclox_src/object.cc b/cclox_src/object.cc
new file mode 100644
index 0000000..32560a6
--- /dev/null
+++ b/cclox_src/object.cc
@@ -0,0 +1,18 @@
+#include "object.hh"
+
+void Identifier::write(std::ostream &os) const {
+  os << identifier;
+};
+
+void StringLit::write(std::ostream &os) const {
+  os << literal;
+};
+
+void Number::write(std::ostream &os) const {
+  os << number;
+};
+
+std::ostream &operator<<(std::ostream &os, const Object &obj) {
+  obj.write(os);
+  return os;
+}
diff --git a/cclox_src/object.hh b/cclox_src/object.hh
new file mode 100644
index 0000000..fd59666
--- /dev/null
+++ b/cclox_src/object.hh
@@ -0,0 +1,27 @@
+#pragma once
+
+#include <string>
+#include <iostream>
+
+struct Object {
+  Object() = delete;
+  virtual ~Object() = default;
+  virtual void write(std::ostream &os) const = 0;
+};
+
+struct Identifier : public Object {
+  virtual void write(std::ostream &os) const final;
+  std::string identifier;
+};
+
+struct StringLit : public Object {
+  virtual void write(std::ostream &os) const final;
+  std::string literal;
+};
+
+struct Number : public Object {
+  virtual void write(std::ostream &os) const final;
+  double number;
+};
+
+std::ostream &operator<<(std::ostream &os, const Object &obj);
diff --git a/cclox_src/scanner.cc b/cclox_src/scanner.cc
new file mode 100644
index 0000000..68259aa
--- /dev/null
+++ b/cclox_src/scanner.cc
@@ -0,0 +1,7 @@
+#include "scanner.hh"
+#include "token.hh"
+#include <vector>
+
+std::vector<Token> Scanner::scan_tokens() {
+  return std::vector<Token>{};
+}
diff --git a/cclox_src/scanner.hh b/cclox_src/scanner.hh
new file mode 100644
index 0000000..ae24ce1
--- /dev/null
+++ b/cclox_src/scanner.hh
@@ -0,0 +1,11 @@
+#pragma once
+
+#include "token.hh"
+#include <vector>
+
+struct Scanner {
+  Scanner(const std::string &code) : code{code} {};
+  std::vector<Token> scan_tokens();
+
+  std::string code;
+};
diff --git a/cclox_src/token.cc b/cclox_src/token.cc
new file mode 100644
index 0000000..a60b490
--- /dev/null
+++ b/cclox_src/token.cc
@@ -0,0 +1,5 @@
+#include "token.hh"
+
+std::ostream &operator<<(std::ostream &os, const Token &token) {
+  return os << uint8_t(token.type) << ' ' << token.lexeme << ' ' << token.literal;
+}
diff --git a/cclox_src/token.hh b/cclox_src/token.hh
new file mode 100644
index 0000000..4f3e88e
--- /dev/null
+++ b/cclox_src/token.hh
@@ -0,0 +1,39 @@
+#pragma once
+
+#include "object.hh"
+#include <cstdint>
+#include <string>
+
+enum class TokenType : uint8_t {
+  // Single-character tokens.
+  LEFT_PAREN, RIGHT_PAREN, LEFT_BRACE, RIGHT_BRACE,
+  COMMA, DOT, MINUS, PLUS, SEMICOLON, SLASH, STAR,
+
+  // One or two character tokens.
+  BANG, BANG_EQUAL,
+  EQUAL, EQUAL_EQUAL,
+  GREATER, GREATER_EQUAL,
+  LESS, LESS_EQUAL,
+
+  // Literals.
+  IDENTIFIER, STRING, NUMBER,
+
+  // Keywords.
+  AND, CLASS, ELSE, FALSE, FUN, FOR, IF, NIL, OR,
+  PRINT, RETURN, SUPER, THIS, TRUE, VAR, WHILE,
+
+  EOFILE,
+};
+
+struct Token {
+  Token(TokenType type, const std::string &lexeme, Object &literal, int line)
+    : type{type}, lexeme{lexeme}, literal{literal}, line{line}
+  {};
+
+  TokenType type;
+  std::string lexeme;
+  Object &literal;
+  int line;
+};
+
+std::ostream &operator<<(std::ostream &os, const Token &token);