diff --git a/README.md b/README.md
index 6903e26..ac33bce 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,7 @@ program = [ "type" type_definitions ";" ]
     [ constant_part ]
     { procedure_definition }
     [ variable_part ]
-    compound_statement ".";
+    "begin" [ statement_list ] "end" ".";
 
 procedure_definition = "proc" ident formal_parameter_list ";" ( block | "extern" ) ";";
 
@@ -45,14 +45,18 @@ block = [ constant_part ]
 constant_part = "const" ident "=" integer { "," ident "=" integer } ";";
 variable_part = "var" variable_declarations ";";
 
-statement = compound_statement
-          | ident ":=" expression
+statement = ident ":=" expression
           | ident actual_parameter_list
-          | "while" condition "do" statement
-          | "if" expression "then" statement [ else statement ];
+          | while_do
+          | if_then_else;
+
+
+while_do = "while" condition "do" [ statement_list ] "end";
+if_then_else = "if" expression
+    "then" [ statement_list ]
+    [ else statement_list ] "end";
 
 statement_list = statement {";" statement };
-compound_statement = "begin" [ statement_list ] "end";
 
 condition = "odd" expression |
             expression ("="|"#"|"<"|"<="|">"|">=") expression;
@@ -86,8 +90,9 @@ variable_declarations = variable_declaration { ";" variable_declaration };
 variable_declaration = ident ":" type_expression;
 
 type_expression = "array" integer "of" type_expression
-                | "^" type_expression
+                | "pointer" "to" type_expression
                 | "record" field_list "end"
+                | "union" field_list "end"
                 | ident;
 
 field_list = field_declaration { ";" field_declaration };
diff --git a/example.elna b/example.elna
index d56148f..9526d90 100644
--- a/example.elna
+++ b/example.elna
@@ -3,6 +3,10 @@ type
   R = record
     x: Int;
     y: Int
+  end,
+  U = union
+    a: Int;
+    b: Int
   end;
 
 proc test_string();
@@ -25,14 +29,13 @@ begin
 
   x := 0;
   while x < 2 do
-  begin
     writei(a[x]);
 	x := x + 1
   end
 end;
 
 proc test_pointer();
-var x: Int, p: ^Int;
+var x: Int, p: pointer to Int;
 begin
   x := 5;
   p := @x;
@@ -55,6 +58,17 @@ begin
   writei(r.y)
 end;
 
+proc test_union();
+var u: U;
+begin
+  writei("");
+  writei("Test union:");
+
+  u.a := 9;
+
+  writei(u.b)
+end;
+
 proc test_primitive();
 var c: Char, z: Float;
 begin
@@ -89,6 +103,7 @@ begin
     writei("Test if: True")
   else
     writei("Test if: False")
+  end
 end;
 
 proc test_not();
@@ -101,6 +116,7 @@ begin
     writei("Test not true.")
   else
     writei("Test not false")
+  end
 end;
 
 proc test_param(d: Int, e: Int);
@@ -132,6 +148,7 @@ begin
   test_not();
   test_param(8, 7);
   test_const_char();
+  test_union();
 
   exit(0)
 end.
diff --git a/gcc/elna-generic.cc b/gcc/elna-generic.cc
index 6e6bfe8..b8a2cb2 100644
--- a/gcc/elna-generic.cc
+++ b/gcc/elna-generic.cc
@@ -15,9 +15,9 @@ namespace elna
 {
 namespace gcc
 {
-    generic_visitor::generic_visitor()
+    generic_visitor::generic_visitor(std::shared_ptr<source::symbol_table<tree>> symbol_table)
     {
-        this->symbol_map = std::make_shared<source::symbol_table<tree>>();
+        this->symbol_map = symbol_table;
     }
 
     void generic_visitor::visit(source::call_statement *statement)
@@ -270,7 +270,7 @@ namespace gcc
         this->current_expression = build_string_literal(string->string().size() + 1, string->string().c_str());
     }
 
-    void generic_visitor::build_binarary_operation(bool condition, source::binary_expression *expression,
+    void generic_visitor::build_binary_operation(bool condition, source::binary_expression *expression,
             tree_code operator_code, tree left, tree right, tree target_type)
     {
         auto expression_location = get_location(&expression->position());
@@ -354,7 +354,7 @@ namespace gcc
         }
         if (operator_code != ERROR_MARK) // An arithmetic operation.
         {
-            build_binarary_operation(left_type == integer_type_node || left_type == double_type_node,
+            build_binary_operation(left_type == integer_type_node || left_type == double_type_node,
                     expression, operator_code, left, right, target_type);
             return;
         }
@@ -373,7 +373,7 @@ namespace gcc
         }
         if (operator_code != ERROR_MARK) // A logical operation.
         {
-            build_binarary_operation(left_type == boolean_type_node,
+            build_binary_operation(left_type == boolean_type_node,
                     expression, operator_code, left, right, target_type);
             return;
         }
@@ -538,7 +538,7 @@ namespace gcc
             tree record_type_node = make_node(RECORD_TYPE);
             tree_chain record_chain;
 
-            for (auto& field : record_type->fields())
+            for (auto& field : record_type->fields)
             {
                 if (field_names.find(field.first) != field_names.cend())
                 {
@@ -564,6 +564,38 @@ namespace gcc
 
             return record_type_node;
         }
+        else if (source::union_type_expression *union_type = type.is_union())
+        {
+            std::set<std::string> field_names;
+            tree union_type_node = make_node(UNION_TYPE);
+            tree_chain union_chain;
+
+            for (auto& field : union_type->fields)
+            {
+                if (field_names.find(field.first) != field_names.cend())
+                {
+                    error_at(get_location(&field.second->position()), "repeated field name");
+                    return error_mark_node;
+                }
+                field_names.insert(field.first);
+
+                tree field_type = build_type(*field.second);
+                if (field_type == NULL_TREE || field_type == error_mark_node)
+                {
+                    return field_type;
+                }
+                tree field_declaration = build_decl(get_location(&field.second->position()),
+                        FIELD_DECL, get_identifier(field.first.c_str()), field_type);
+                TREE_ADDRESSABLE(field_declaration) = 1;
+                DECL_CONTEXT(field_declaration) = union_type_node;
+
+                union_chain.append(field_declaration);
+            }
+            TYPE_FIELDS(union_type_node) = union_chain.head();
+            layout_type(union_type_node);
+
+            return union_type_node;
+        }
         return NULL_TREE;
     }
 
diff --git a/gcc/elna-tree.cc b/gcc/elna-tree.cc
index 3e91f74..6cac5ee 100644
--- a/gcc/elna-tree.cc
+++ b/gcc/elna-tree.cc
@@ -34,12 +34,6 @@ namespace gcc
         return TREE_CODE(type) == ARRAY_TYPE;
     }
 
-    bool is_record_type(tree type)
-    {
-        gcc_assert(TYPE_P(type));
-        return TREE_CODE(type) == RECORD_TYPE;
-    }
-
     tree tree_chain_base::head()
     {
         return first;
@@ -79,5 +73,10 @@ namespace gcc
     {
         return m_block;
     }
+
+    std::shared_ptr<elna::source::symbol_table<tree>> builtin_symbol_table()
+    {
+        return std::make_shared<elna::source::symbol_table<tree>>();
+    }
 }
 }
diff --git a/include/elna/gcc/elna-generic.h b/include/elna/gcc/elna-generic.h
index 96d6856..905d376 100644
--- a/include/elna/gcc/elna-generic.h
+++ b/include/elna/gcc/elna-generic.h
@@ -31,11 +31,11 @@ namespace gcc
         void enter_scope();
         tree_symbol_mapping leave_scope();
 
-        void build_binarary_operation(bool condition, source::binary_expression *expression,
+        void build_binary_operation(bool condition, source::binary_expression *expression,
             tree_code operator_code, tree left, tree right, tree target_type);
 
     public:
-        generic_visitor();
+        generic_visitor(std::shared_ptr<source::symbol_table<tree>> symbol_table);
 
         void visit(source::program *program) override;
         void visit(source::procedure_definition *definition) override;
diff --git a/include/elna/gcc/elna-tree.h b/include/elna/gcc/elna-tree.h
index a4ecdd5..64f5e31 100644
--- a/include/elna/gcc/elna-tree.h
+++ b/include/elna/gcc/elna-tree.h
@@ -26,7 +26,6 @@ namespace gcc
     bool is_pointer_type(tree type);
     bool is_string_type(tree type);
     bool is_array_type(tree type);
-    bool is_record_type(tree type);
 
     class tree_chain_base
     {
@@ -58,5 +57,7 @@ namespace gcc
         tree bind_expression();
         tree block();
     };
+
+    std::shared_ptr<elna::source::symbol_table<tree>> builtin_symbol_table();
 }
 }
diff --git a/include/elna/source/ast.h b/include/elna/source/ast.h
index dd99e53..d363aa9 100644
--- a/include/elna/source/ast.h
+++ b/include/elna/source/ast.h
@@ -52,6 +52,7 @@ namespace source
     class array_type_expression;
     class pointer_type_expression;
     class record_type_expression;
+    class union_type_expression;
     class variable_expression;
     class array_access_expression;
     class field_access_expression;
@@ -83,6 +84,7 @@ namespace source
         virtual void visit(array_type_expression *) = 0;
         virtual void visit(pointer_type_expression *) = 0;
         virtual void visit(record_type_expression *) = 0;
+        virtual void visit(union_type_expression *) = 0;
         virtual void visit(variable_expression *) = 0;
         virtual void visit(array_access_expression *) = 0;
         virtual void visit(field_access_expression *is_field_access) = 0;
@@ -116,6 +118,7 @@ namespace source
         virtual void visit(array_type_expression *expression) override;
         virtual void visit(pointer_type_expression *) override;
         virtual void visit(record_type_expression *expression) override;
+        virtual void visit(union_type_expression *expression) override;
         virtual void visit(variable_expression *) override;
         virtual void visit(array_access_expression *expression) override;
         virtual void visit(field_access_expression *expression) override;
@@ -253,6 +256,7 @@ namespace source
         virtual array_type_expression *is_array();
         virtual pointer_type_expression *is_pointer();
         virtual record_type_expression *is_record();
+        virtual union_type_expression *is_union();
 
     protected:
         type_expression(const struct position position);
@@ -310,23 +314,36 @@ namespace source
         virtual ~pointer_type_expression() override;
     };
 
-    class record_type_expression final : public type_expression
+    using field_t = std::pair<std::string, type_expression *>;
+    using fields_t = std::vector<field_t>;
+
+    class composite_type_expression : public type_expression
+    {
+    protected:
+        composite_type_expression(const struct position position, fields_t&& fields);
+
+    public:
+        fields_t fields;
+
+        virtual ~composite_type_expression() override;
+    };
+
+    class record_type_expression final : public composite_type_expression
     {
     public:
-        using field_t = std::pair<std::string, type_expression *>;
-        using fields_t = std::vector<field_t>;
-
         record_type_expression(const struct position position, fields_t&& fields);
+
         virtual void accept(parser_visitor *visitor) override;
-
-        fields_t& fields();
-
         record_type_expression *is_record() override;
+    };
 
-        virtual ~record_type_expression() override;
+    class union_type_expression final : public composite_type_expression
+    {
+    public:
+        union_type_expression(const struct position position, fields_t&& fields);
 
-    private:
-        fields_t m_fields;
+        virtual void accept(parser_visitor *visitor) override;
+        union_type_expression *is_union() override;
     };
 
     /**
@@ -443,13 +460,11 @@ namespace source
 
     class compound_statement : public statement
     {
-        std::vector<statement *> m_statements;
-
     public:
-        explicit compound_statement(const struct position position);
-        virtual void accept(parser_visitor *visitor) override;
+        std::vector<statement *> statements;
 
-        std::vector<statement *>& statements();
+        compound_statement(const struct position position, std::vector<statement *>&& statements);
+        virtual void accept(parser_visitor *visitor) override;
 
         virtual ~compound_statement() override;
     };
@@ -556,8 +571,8 @@ namespace source
     class if_statement : public statement
     {
         expression *m_prerequisite;
-        statement *m_body;
-        statement *m_alternative;
+        compound_statement *m_body;
+        compound_statement *m_alternative;
 
     public:
         /**
@@ -567,12 +582,12 @@ namespace source
          * \param alternative Statement executed if the condition is not met.
          */
         if_statement(const struct position position, expression *prerequisite,
-                statement *body, statement *alternative = nullptr);
+                compound_statement *body, compound_statement *alternative = nullptr);
         virtual void accept(parser_visitor *visitor) override;
 
         expression& prerequisite();
-        statement& body();
-        statement *alternative();
+        compound_statement& body();
+        compound_statement *alternative();
 
         virtual ~if_statement() override;
     };
@@ -583,7 +598,7 @@ namespace source
     class while_statement : public statement
     {
         expression *m_prerequisite;
-        statement *m_body;
+        compound_statement *m_body;
 
     public:
         /**
@@ -592,11 +607,11 @@ namespace source
          * \param body Statement executed while the condition is met.
          */
         while_statement(const struct position position, expression *prerequisite,
-                statement *body);
+                compound_statement *body);
         virtual void accept(parser_visitor *visitor) override;
 
         expression& prerequisite();
-        statement& body();
+        compound_statement& body();
 
         virtual ~while_statement() override;
     };
diff --git a/source/ast.cc b/source/ast.cc
index fdbe984..07d6837 100644
--- a/source/ast.cc
+++ b/source/ast.cc
@@ -43,7 +43,7 @@ namespace source
 
     void empty_visitor::visit(compound_statement *statement)
     {
-        for (auto& nested_statement : statement->statements())
+        for (const auto nested_statement : statement->statements)
         {
             nested_statement->accept(this);
         }
@@ -114,7 +114,15 @@ namespace source
 
     void empty_visitor::visit(record_type_expression *expression)
     {
-        for (auto& field : expression->fields())
+        for (auto& field : expression->fields)
+        {
+            field.second->accept(this);
+        }
+    }
+
+    void empty_visitor::visit(union_type_expression *expression)
+    {
+        for (auto& field : expression->fields)
         {
             field.second->accept(this);
         }
@@ -244,6 +252,11 @@ namespace source
         return nullptr;
     }
 
+    union_type_expression *type_expression::is_union()
+    {
+        return nullptr;
+    }
+
     pointer_type_expression *type_expression::is_pointer()
     {
         return nullptr;
@@ -321,9 +334,23 @@ namespace source
         delete m_base;
     }
 
+    composite_type_expression::composite_type_expression(const struct position position,
+            fields_t&& fields)
+        : type_expression(position), fields(std::move(fields))
+    {
+    }
+
+    composite_type_expression::~composite_type_expression()
+    {
+        for (auto& field_declaration : fields)
+        {
+            delete field_declaration.second;
+        }
+    }
+
     record_type_expression::record_type_expression(const struct position position,
-            record_type_expression::fields_t&& fields)
-        : type_expression(position), m_fields(std::move(fields))
+            fields_t&& fields)
+        : composite_type_expression(position, std::move(fields))
     {
     }
 
@@ -332,22 +359,25 @@ namespace source
         visitor->visit(this);
     }
 
-    record_type_expression::fields_t& record_type_expression::fields()
-    {
-        return m_fields;
-    }
-
     record_type_expression *record_type_expression::is_record()
     {
         return this;
     }
 
-    record_type_expression::~record_type_expression()
+    union_type_expression::union_type_expression(const struct position position,
+            fields_t&& fields)
+        : composite_type_expression(position, std::move(fields))
     {
-        for (auto& field_declaration : fields())
-        {
-            delete field_declaration.second;
-        }
+    }
+
+    union_type_expression *union_type_expression::is_union()
+    {
+        return this;
+    }
+
+    void union_type_expression::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
     }
 
     variable_declaration::variable_declaration(const struct position position, const std::string& identifier,
@@ -766,8 +796,8 @@ namespace source
         }
     }
 
-    compound_statement::compound_statement(const struct position position)
-        : statement(position)
+    compound_statement::compound_statement(const struct position position, std::vector<statement *>&& statements)
+        : statement(position), statements(std::move(statements))
     {
     }
 
@@ -776,14 +806,9 @@ namespace source
         visitor->visit(this);
     }
 
-    std::vector<statement *>& compound_statement::statements()
-    {
-        return m_statements;
-    }
-
     compound_statement::~compound_statement()
     {
-        for (auto statement : m_statements)
+        for (auto statement : statements)
         {
             delete statement;
         }
@@ -836,7 +861,7 @@ namespace source
     }
 
     if_statement::if_statement(const struct position position, expression *prerequisite,
-            statement *body, statement *alternative)
+            compound_statement *body, compound_statement *alternative)
         : statement(position), m_prerequisite(prerequisite), m_body(body),
         m_alternative(alternative)
     {
@@ -852,12 +877,12 @@ namespace source
         return *m_prerequisite;
     }
 
-    statement& if_statement::body()
+    compound_statement& if_statement::body()
     {
         return *m_body;
     }
 
-    statement *if_statement::alternative()
+    compound_statement *if_statement::alternative()
     {
         return m_alternative;
     }
@@ -874,7 +899,7 @@ namespace source
     }
 
     while_statement::while_statement(const struct position position, expression *prerequisite,
-            statement *body)
+            compound_statement *body)
         : statement(position), m_prerequisite(prerequisite), m_body(body)
     {
     }
@@ -889,7 +914,7 @@ namespace source
         return *m_prerequisite;
     }
 
-    statement& while_statement::body()
+    compound_statement& while_statement::body()
     {
         return *m_body;
     }
diff --git a/source/lexer.ll b/source/lexer.ll
index 6f5c397..75c1925 100644
--- a/source/lexer.ll
+++ b/source/lexer.ll
@@ -76,6 +76,15 @@ type                    {
 record                  {
                             return yy::parser::make_RECORD(this->location);
                         }
+union                   {
+                            return yy::parser::make_UNION(this->location);
+                        }
+pointer                 {
+                            return yy::parser::make_POINTER(this->location);
+                        }
+to                      {
+                            return yy::parser::make_TO(this->location);
+                        }
 true                    {
                             return yy::parser::make_BOOLEAN(true, this->location);
                         }
diff --git a/source/parser.yy b/source/parser.yy
index 57aaf5a..06582bc 100644
--- a/source/parser.yy
+++ b/source/parser.yy
@@ -62,8 +62,8 @@
 %token <std::string> CHARACTER "character"
 %token <std::string> STRING "string"
 %token <bool> BOOLEAN
-%token IF WHILE DO
-%token CONST VAR PROCEDURE ARRAY OF TYPE RECORD
+%token IF WHILE DO THEN ELSE
+%token CONST VAR PROCEDURE ARRAY OF TYPE RECORD POINTER TO UNION
 %token BEGIN_BLOCK END_BLOCK EXTERN
 %token LEFT_PAREN RIGHT_PAREN LEFT_SQUARE RIGHT_SQUARE SEMICOLON DOT COMMA
 %token AND OR NOT
@@ -71,9 +71,6 @@
 %token PLUS MINUS MULTIPLICATION DIVISION
 %token ASSIGNMENT COLON HAT AT
 
-%precedence THEN
-%precedence ELSE
-
 %type <elna::source::literal *> literal;
 %type <elna::source::constant_definition *> constant_definition;
 %type <std::vector<elna::source::constant_definition *>> constant_part constant_definitions;
@@ -84,7 +81,6 @@
 %type <elna::source::expression *> expression pointer summand factor comparand logical_operand;
 %type <std::vector<elna::source::expression *>> expressions actual_parameter_list;
 %type <elna::source::designator_expression *> designator_expression;
-%type <elna::source::compound_statement *> compound_statement;
 %type <elna::source::assign_statement *> assign_statement;
 %type <elna::source::call_statement *> call_statement;
 %type <elna::source::while_statement *> while_statement;
@@ -167,11 +163,6 @@ procedure_definitions:
 procedure_part:
     /* no procedure definitions */ {}
     | procedure_definitions { std::swap($$, $1); }
-compound_statement: BEGIN_BLOCK optional_statements END_BLOCK
-        {
-            $$ = new elna::source::compound_statement(elna::source::make_position(@1));
-            std::swap($$->statements(), $2);
-        }
 assign_statement: designator_expression ASSIGNMENT expression
         {
             $$ = new elna::source::assign_statement(elna::source::make_position(@1), $1, $3);
@@ -181,21 +172,22 @@ call_statement: IDENTIFIER actual_parameter_list
             $$ = new elna::source::call_statement(elna::source::make_position(@1), $1);
             std::swap($$->arguments(), $2);
         }
-while_statement: WHILE expression DO statement
+while_statement: WHILE expression DO optional_statements END_BLOCK
         {
-            $$ = new elna::source::while_statement(elna::source::make_position(@1),
-                $2, $4);
+            auto body = new elna::source::compound_statement(elna::source::make_position(@3), std::move($4));
+            $$ = new elna::source::while_statement(elna::source::make_position(@1), $2, body);
         }
 if_statement:
-    IF expression THEN statement
+    IF expression THEN optional_statements END_BLOCK
         {
-            $$ = new elna::source::if_statement(elna::source::make_position(@1),
-                $2, $4);
+            auto then = new elna::source::compound_statement(elna::source::make_position(@3), std::move($4));
+            $$ = new elna::source::if_statement(elna::source::make_position(@1), $2, then);
         }
-    | IF expression THEN statement ELSE statement
+    | IF expression THEN optional_statements ELSE optional_statements END_BLOCK
         {
-            $$ = new elna::source::if_statement(elna::source::make_position(@1),
-                $2, $4, $6);
+            auto then = new elna::source::compound_statement(elna::source::make_position(@3), std::move($4));
+            auto _else = new elna::source::compound_statement(elna::source::make_position(@5), std::move($6));
+            $$ = new elna::source::if_statement(elna::source::make_position(@1), $2, then, _else);
         }
 literal:
     INTEGER
@@ -315,8 +307,7 @@ designator_expression:
             $$ = new elna::source::variable_expression(elna::source::make_position(@1), $1);
         }
 statement:
-    compound_statement { $$ = $1; }
-    | assign_statement { $$ = $1; }
+    assign_statement { $$ = $1; }
     | call_statement { $$ = $1; }
     | while_statement { $$ = $1; }
     | if_statement { $$ = $1; }
@@ -344,14 +335,18 @@ type_expression:
         {
             $$ = new elna::source::array_type_expression(elna::source::make_position(@1), $4, $2);
         }
-    | HAT type_expression
+    | POINTER TO type_expression
         {
-            $$ = new elna::source::pointer_type_expression(elna::source::make_position(@1), $2);
+            $$ = new elna::source::pointer_type_expression(elna::source::make_position(@1), $3);
         }
     | RECORD field_list END_BLOCK
         {
             $$ = new elna::source::record_type_expression(elna::source::make_position(@1), std::move($2));
         }
+    | UNION field_list END_BLOCK
+        {
+            $$ = new elna::source::union_type_expression(elna::source::make_position(@1), std::move($2));
+        }
     | IDENTIFIER
         {
             $$ = new elna::source::basic_type_expression(elna::source::make_position(@1), $1);
@@ -359,7 +354,7 @@ type_expression:
 variable_declaration: IDENTIFIER COLON type_expression
         {
             $$ = new elna::source::variable_declaration(elna::source::make_position(@1), $1, $3);
-        };
+        }
 variable_declarations:
     variable_declaration COMMA variable_declarations
         {