diff --git a/projects/07/calculator/CMakeLists.txt b/projects/07/calculator/CMakeLists.txt
index c3bbaf8..14b4d29 100644
--- a/projects/07/calculator/CMakeLists.txt
+++ b/projects/07/calculator/CMakeLists.txt
@@ -7,6 +7,8 @@ project(${TARGET} LANGUAGES CXX)
 add_executable(
     ${TARGET}
     calculator.cpp
+    token.cpp
+    variable.cpp
 )
 
 install(TARGETS ${TARGET})
diff --git a/projects/07/calculator/calculator.cpp b/projects/07/calculator/calculator.cpp
index d1bf53e..f70c992 100644
--- a/projects/07/calculator/calculator.cpp
+++ b/projects/07/calculator/calculator.cpp
@@ -5,189 +5,8 @@
 
 #include <std_lib_facilities.h>
 
-struct Token
-{
-  char kind;
-  double value;
-  string name;
-
-  Token(char ch) : kind{ch}, value{0} {}
-
-  Token(char ch, double val) : kind{ch}, value{val} {}
-
-  Token(char ch, string id) : kind{ch}, name{id} {}
-};
-
-class Token_stream
-{
-  bool full{false};
-  Token buffer{'\0'};
-
-public:
-  Token_stream() {}
-
-  Token get ();
-  void putback (Token t);
-
-  void ignore (char);
-};
-
-void Token_stream::putback(Token t)
-{
-  if (full)
-    error("putback() into a full buffer");
-
-  buffer = t;
-  full = true;
-}
-
-constexpr char quit = 'q';
-constexpr char print = ';';
-constexpr char number = '8';
-constexpr char name = 'a';
-constexpr char let = 'L';
-
-const string prompt = "> ";
-const string result = "= ";
-const string declkey = "let";
-const string quitkey = "quit";
-
-Token Token_stream::get()
-{
-  if (full)
-  {
-    full = false;
-    return buffer;
-  }
-
-  char ch;
-  cin >> ch;
-
-  switch (ch)
-  {
-  case '(':
-  case ')':
-  case '+':
-  case '-':
-  case '*':
-  case '/':
-  case '%':
-  case print:
-  case '=':
-    return Token{ch};
-
-  case '.':
-  case '0':
-  case '1':
-  case '2':
-  case '3':
-  case '4':
-  case '5':
-  case '6':
-  case '7':
-  case '8':
-  case '9':
-  {
-    cin.putback(ch);
-    double val;
-    cin >> val;
-    return Token{number, val};
-  }
-
-  default:
-    if (isalpha(ch))
-    {
-      string s;
-      s += ch;
-      while (cin.get(ch) && (isalpha(ch) || isdigit(ch)))
-        s += ch;
-      cin.putback(ch);
-
-      if (s == declkey)
-        return Token{let};
-
-      if (s == quitkey)
-        return Token{quit};
-
-      return Token{name, s};
-    }
-    error("bad token");
-  }
-}
-
-void Token_stream::ignore(char c)
-{
-  if (full && c == buffer.kind)
-  {
-    full = false;
-    return;
-  }
-  full = false;
-
-  for (char ch; cin >> ch;)
-  {
-    if (ch == c)
-      return;
-  }
-}
-
-struct Variable
-{
-  string name;
-  double value;
-
-  Variable(string n, double v) : name{n}, value{v} {}
-};
-
-vector<Variable> var_table;
-
-double get_value (const string& s)
-{
-  for (const auto& var : var_table)
-  {
-    if (var.name == s)
-      return var.value;
-  }
-
-  error("get: undefined name ", s);
-}
-
-void set_value (const string& s, double d)
-{
-  for (auto& var : var_table)
-  {
-    if (var.name == s)
-    {
-      var.value = d;
-      return;
-    }
-  }
-
-  error("set: undefined name ", s);
-}
-
-bool is_declared (const string& s)
-{
-  for (const auto& var : var_table)
-  {
-    if (var.name == s)
-      return true;
-  }
-
-  return false;
-}
-
-double define_name (const string& var, double val)
-{
-  if (is_declared(var))
-    error(var, " declared twice");
-
-  var_table.push_back(Variable{var, val});
-
-  return val;
-}
-
-Token_stream ts;
+#include "token.h"
+#include "variable.h"
 
 double expression ();
 
@@ -315,8 +134,6 @@ double statement ()
   }
 }
 
-void clean_up_mess () { ts.ignore(print); }
-
 void calculate ()
 {
   while (true)
diff --git a/projects/07/calculator/test_ans.txt b/projects/07/calculator/test_ans.txt
new file mode 100644
index 0000000..f002515
--- /dev/null
+++ b/projects/07/calculator/test_ans.txt
@@ -0,0 +1,54 @@
+> = 0
+> = 1
+> = 2
+> = 3
+> = 4
+> = 5
+> = 6
+> = 7
+> = 8
+> = 9
+> = 3
+> = 3
+> = 6
+> = -1
+> = -1
+> = -4
+> = 2
+> = 2
+> = 6
+> = 0.5
+> = 0.5
+> = 0.166667
+> = 7
+> = -5
+> = 1.66667
+> = 0.333333
+> = divide by zero
+> = primary expected
+> = 3
+> = -3
+> = 3
+> = -3
+> = 3
+> = 10
+> = 21
+> = divide by zero
+> = bad token
+> = bad token
+> = 1
+> = 21
+> = -4.5
+> = 0
+> = 0
+> = 2
+> = 0
+> = 4.2
+> = 3.3
+> = 0.2
+> = 2
+> = 3
+> = 0
+> = 5
+> = 1
+> 
\ No newline at end of file
diff --git a/projects/07/calculator/test_in.txt b/projects/07/calculator/test_in.txt
new file mode 100644
index 0000000..037dc66
--- /dev/null
+++ b/projects/07/calculator/test_in.txt
@@ -0,0 +1,50 @@
+0; 1; 2; 3; 4; 5; 6; 7; 8; 9;
+
+1 + 2;  1+2;  1 + 2 + 3;
+1 - 2;  1-2;  1 - 2 - 3;
+
+1 * 2;  1*2;  1 * 2 * 3;
+1 / 2;  1/2;  1 / 2 / 3;
+
+1 + 2*3;  1 - 2*3;
+1 + 2/3;  1 - 2/3;
+
+3/0;
+
+();
+(3);
+-(3);
++(3);
+(-3);
+(+3);
+(3+7);
+(3*7);
+
+3 / (3 - 3);
+
+3 * 4&5;
+
+93"43-189'3dfrer4734***&340#$%%%8340909909()()*(&)))((( ;
+
+4 / (2 + 2*1);
+1 + 4 * (2 + 3/2*2);
+
+72 / (10*(9-5) - 7*8);
+
++2 - 2;  -2 + 2;
+
+2 % 4;
+4 % 2;
+4.2 % 8;
+3.3 % 6.6;
+6.8 % 3.3;
+
+let x = 2;  let q=3;
+
+x*q - (x * q);
+
+q + x;
+
+x/(x + 2*q - q*2);
+
+quit
diff --git a/projects/07/calculator/token.cpp b/projects/07/calculator/token.cpp
new file mode 100644
index 0000000..ae6e1c1
--- /dev/null
+++ b/projects/07/calculator/token.cpp
@@ -0,0 +1,93 @@
+#include "token.h"
+
+Token_stream ts;
+
+void Token_stream::putback(Token t)
+{
+  if (full)
+    error("putback() into a full buffer");
+
+  buffer = t;
+  full = true;
+}
+
+Token Token_stream::get()
+{
+  if (full)
+  {
+    full = false;
+    return buffer;
+  }
+
+  char ch;
+  cin >> ch;
+
+  switch (ch)
+  {
+  case '(':
+  case ')':
+  case '+':
+  case '-':
+  case '*':
+  case '/':
+  case '%':
+  case print:
+  case '=':
+    return Token{ch};
+
+  case '.':
+  case '0':
+  case '1':
+  case '2':
+  case '3':
+  case '4':
+  case '5':
+  case '6':
+  case '7':
+  case '8':
+  case '9':
+  {
+    cin.putback(ch);
+    double val;
+    cin >> val;
+    return Token{number, val};
+  }
+
+  default:
+    if (isalpha(ch))
+    {
+      string s;
+      s += ch;
+      while (cin.get(ch) && (isalpha(ch) || isdigit(ch)))
+        s += ch;
+      cin.putback(ch);
+
+      if (s == declkey)
+        return Token{let};
+
+      if (s == quitkey)
+        return Token{quit};
+
+      return Token{name, s};
+    }
+    error("bad token");
+  }
+}
+
+void Token_stream::ignore(char c)
+{
+  if (full && c == buffer.kind)
+  {
+    full = false;
+    return;
+  }
+  full = false;
+
+  for (char ch; cin >> ch;)
+  {
+    if (ch == c)
+      return;
+  }
+}
+
+void clean_up_mess () { ts.ignore(print); }
\ No newline at end of file
diff --git a/projects/07/calculator/token.h b/projects/07/calculator/token.h
new file mode 100644
index 0000000..9ad3c8d
--- /dev/null
+++ b/projects/07/calculator/token.h
@@ -0,0 +1,48 @@
+#ifndef TOKEN_H
+#define TOKEN_H 1
+
+#include <std_lib_facilities.h>
+
+struct Token
+{
+  char kind;
+  double value;
+  string name;
+
+  Token(char ch) : kind{ch}, value{0} {}
+
+  Token(char ch, double val) : kind{ch}, value{val} {}
+
+  Token(char ch, string id) : kind{ch}, name{id} {}
+};
+
+class Token_stream
+{
+  bool full{false};
+  Token buffer{'\0'};
+
+public:
+  Token_stream() {}
+
+  Token get ();
+  void putback (Token t);
+
+  void ignore (char);
+};
+
+extern Token_stream ts;
+
+constexpr char quit = 'q';
+constexpr char print = ';';
+constexpr char number = '8';
+constexpr char name = 'a';
+constexpr char let = 'L';
+
+const string prompt = "> ";
+const string result = "= ";
+const string declkey = "let";
+const string quitkey = "quit";
+
+void clean_up_mess ();
+
+#endif  // #ifndef TOKEN_H
\ No newline at end of file
diff --git a/projects/07/calculator/variable.cpp b/projects/07/calculator/variable.cpp
new file mode 100644
index 0000000..09b1775
--- /dev/null
+++ b/projects/07/calculator/variable.cpp
@@ -0,0 +1,49 @@
+#include "variable.h"
+
+vector<Variable> var_table;
+
+double get_value (const string& s)
+{
+  for (const auto& var : var_table)
+  {
+    if (var.name == s)
+      return var.value;
+  }
+
+  error("get: undefined name ", s);
+}
+
+void set_value (const string& s, double d)
+{
+  for (auto& var : var_table)
+  {
+    if (var.name == s)
+    {
+      var.value = d;
+      return;
+    }
+  }
+
+  error("set: undefined name ", s);
+}
+
+bool is_declared (const string& s)
+{
+  for (const auto& var : var_table)
+  {
+    if (var.name == s)
+      return true;
+  }
+
+  return false;
+}
+
+double define_name (const string& var, double val)
+{
+  if (is_declared(var))
+    error(var, " declared twice");
+
+  var_table.push_back(Variable{var, val});
+
+  return val;
+}
\ No newline at end of file
diff --git a/projects/07/calculator/variable.h b/projects/07/calculator/variable.h
new file mode 100644
index 0000000..5a4afc8
--- /dev/null
+++ b/projects/07/calculator/variable.h
@@ -0,0 +1,21 @@
+#ifndef VARIABLE_H
+#define VARIABLE_H 1
+
+#include <std_lib_facilities.h>
+
+struct Variable
+{
+  string name;
+  double value;
+
+  Variable(string n, double v) : name{n}, value{v} {}
+};
+
+extern vector<Variable> var_table;
+
+double get_value (const string& s);
+void set_value (const string& s, double d);
+bool is_declared (const string& s);
+double define_name (const string& var, double val);
+
+#endif  // #ifndef VARIABLE_H
\ No newline at end of file