diff --git a/README.md b/README.md
index 58f49a7..e0f9b5d 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,8 @@ integer = digit { digit };
 float = integer "." integer;
 boolean = "true" | "false";
 
+literal = integer | float | boolean | "'" character "'" | """ { character } """;
+
 program = [ "type" type_definitions ";" ]
     [ constant_part ]
     { procedure_definition }
@@ -64,11 +66,7 @@ comparand = summand { ("+" | "-") summand };
 summand = factor { ("*" | "/") factor };
 factor = pointer { unary_prefix pointer };
 
-pointer = integer
-        | float
-        | boolean
-        | "'" character "'"
-        | """ { character } """
+pointer = literal
         | designator_expression { $$ = $1; }
         | "(" expression ")";
 
diff --git a/example.elna b/example.elna
index 3d04501..c2b216c 100644
--- a/example.elna
+++ b/example.elna
@@ -103,6 +103,22 @@ begin
     writei("Test not false")
 end;
 
+proc test_param(d: Int, e: Int);
+begin
+  writei("");
+  writei("Test param");
+  writei(d);
+  writei(e)
+end;
+
+proc test_const_char();
+const x = 'u';
+begin
+  writei("");
+  writei("Test constant character");
+  writei(x)
+end;
+
 begin
   test_primitive();
   test_string();
@@ -111,5 +127,7 @@ begin
   test_record();
   test_const();
   test_if();
-  test_not()
+  test_not();
+  test_param(8, 7);
+  test_const_char()
 end.
diff --git a/gcc/elna-generic.cc b/gcc/elna-generic.cc
index 0cfbf47..988c82f 100644
--- a/gcc/elna-generic.cc
+++ b/gcc/elna-generic.cc
@@ -87,10 +87,17 @@ namespace gcc
         }
         else if (symbol)
         {
-            tree fndecl_type = build_function_type_list(integer_type_node, NULL_TREE);
+            tree fndecl_type = build_function_type(void_type_node, TYPE_ARG_TYPES(symbol->payload));
             tree printf_fn = build1(ADDR_EXPR, build_pointer_type(fndecl_type), symbol->payload);
 
-            tree stmt = build_call_nary(integer_type_node, printf_fn, 0);
+            std::vector<tree> arguments(statement->arguments().size());
+            for (std::size_t i = 0; i < statement->arguments().size(); ++i)
+            {
+                statement->arguments().at(i)->accept(this);
+                arguments[i] = this->current_expression;
+            }
+            tree stmt = build_call_array_loc(get_location(&statement->position()),
+                    void_type_node, printf_fn, arguments.size(), arguments.data());
 
             append_to_statement_list(stmt, &this->current_statements);
             this->current_expression = NULL_TREE;
@@ -122,7 +129,7 @@ namespace gcc
         tree set_result = build2(INIT_EXPR, void_type_node, DECL_RESULT(main_fndecl),
                 build_int_cst_type(integer_type_node, 0));
         tree return_stmt = build1(RETURN_EXPR, void_type_node, set_result);
-       
+
         enter_scope();
 
         for (const auto& definition : program->value_definitions)
@@ -133,29 +140,29 @@ namespace gcc
 
         append_to_statement_list(return_stmt, &this->current_statements);
         tree_symbol_mapping mapping = leave_scope();
-       
+
         BLOCK_SUPERCONTEXT(mapping.block()) = this->main_fndecl;
         DECL_INITIAL(this->main_fndecl) = mapping.block();
         DECL_SAVED_TREE(this->main_fndecl) = mapping.bind_expression();
-       
+
         DECL_EXTERNAL(this->main_fndecl) = 0;
         DECL_PRESERVE_P(this->main_fndecl) = 1;
-       
+
         gimplify_function_tree(this->main_fndecl);
-       
+
         cgraph_node::finalize_function(this->main_fndecl, true);
     }
 
     void generic_visitor::visit(source::procedure_definition *definition)
     {
-        tree *parameter_types = reinterpret_cast<tree *>(xmalloc(definition->parameters().size() * sizeof(tree)));
+        std::vector<tree> parameter_types(definition->parameters().size());
 
         for (std::size_t i = 0; i < definition->parameters().size(); ++i)
         {
             parameter_types[i] = build_type(definition->parameters().at(i)->type());
         }
         tree declaration_type = build_function_type_array(void_type_node,
-                definition->parameters().size(), parameter_types);
+                definition->parameters().size(), parameter_types.data());
         this->main_fndecl = build_fn_decl(definition->identifier().c_str(), declaration_type);
 
         this->symbol_map->enter(definition->identifier(), source::make_info(this->main_fndecl));
@@ -166,6 +173,21 @@ namespace gcc
         DECL_RESULT(this->main_fndecl) = resdecl;
 
         enter_scope();
+
+        gcc::tree_chain argument_chain;
+        for (std::size_t i = 0; i < definition->parameters().size(); ++i)
+        {
+            auto parameter = definition->parameters().at(i);
+
+            tree declaration_tree = build_decl(get_location(&parameter->position()), PARM_DECL,
+                get_identifier(parameter->identifier().c_str()), parameter_types[i]);
+            DECL_CONTEXT(declaration_tree) = this->main_fndecl;
+            DECL_ARG_TYPE(declaration_tree) = parameter_types[i];
+
+            this->symbol_map->enter(parameter->identifier(), source::make_info(declaration_tree));
+            argument_chain.append(declaration_tree);
+        }
+        DECL_ARGUMENTS(this->main_fndecl) = argument_chain.head();
         definition->body().accept(this);
 
         tree_symbol_mapping mapping = leave_scope();
@@ -180,8 +202,6 @@ namespace gcc
         gimplify_function_tree(this->main_fndecl);
 
         cgraph_node::finalize_function(this->main_fndecl, true);
-
-        free(parameter_types);
     }
 
     void generic_visitor::enter_scope()
@@ -227,9 +247,9 @@ namespace gcc
         this->current_expression = build_int_cst_type(boolean_type_node, boolean->number());
     }
 
-    void generic_visitor::visit(source::char_literal *character)
+    void generic_visitor::visit(source::number_literal<unsigned char> *character)
     {
-        this->current_expression = build_int_cstu(elna_char_type_node, character->character());
+        this->current_expression = build_int_cstu(elna_char_type_node, character->number());
     }
 
     void generic_visitor::visit(source::string_literal *string)
@@ -385,15 +405,15 @@ namespace gcc
     void generic_visitor::visit(source::constant_definition *definition)
     {
         location_t definition_location = get_location(&definition->position());
+        definition->body().accept(this);
+
         tree definition_tree = build_decl(definition_location, CONST_DECL,
-                get_identifier(definition->identifier().c_str()), integer_type_node);
+                get_identifier(definition->identifier().c_str()), TREE_TYPE(this->current_expression));
         auto result = this->symbol_map->enter(definition->identifier(), source::make_info(definition_tree));
 
         if (result)
         {
-            definition->body().accept(this);
-
-            DECL_INITIAL(definition_tree) = build_int_cst_type(integer_type_node, definition->body().number());
+            DECL_INITIAL(definition_tree) = this->current_expression;
             TREE_CONSTANT(definition_tree) = 1;
             TREE_READONLY(definition_tree) = 1;
 
diff --git a/include/elna/gcc/elna-generic.h b/include/elna/gcc/elna-generic.h
index 7019bc9..96d6856 100644
--- a/include/elna/gcc/elna-generic.h
+++ b/include/elna/gcc/elna-generic.h
@@ -43,7 +43,7 @@ namespace gcc
         void visit(source::number_literal<std::int32_t> *literal) override;
         void visit(source::number_literal<double> *literal) override;
         void visit(source::number_literal<bool> *boolean) override;
-        void visit(source::char_literal *character) override;
+        void visit(source::number_literal<unsigned char> *character) override;
         void visit(source::string_literal *string) override;
         void visit(source::binary_expression *expression) override;
         void visit(source::unary_expression *expression) override;
diff --git a/include/elna/source/ast.h b/include/elna/source/ast.h
index b30ccb0..99ad8cc 100644
--- a/include/elna/source/ast.h
+++ b/include/elna/source/ast.h
@@ -90,7 +90,7 @@ namespace source
         virtual void visit(number_literal<std::int32_t> *) = 0;
         virtual void visit(number_literal<double> *) = 0;
         virtual void visit(number_literal<bool> *) = 0;
-        virtual void visit(char_literal *) = 0;
+        virtual void visit(number_literal<unsigned char> *) = 0;
         virtual void visit(string_literal *) = 0;
     };
 
@@ -123,7 +123,7 @@ namespace source
         virtual void visit(number_literal<std::int32_t> *) override;
         virtual void visit(number_literal<double> *) override;
         virtual void visit(number_literal<bool> *) override;
-        virtual void visit(char_literal *) override;
+        virtual void visit(number_literal<unsigned char> *) override;
         virtual void visit(string_literal *) override;
     };
 
@@ -353,12 +353,18 @@ namespace source
         virtual ~variable_declaration() override;
     };
 
+    class literal : public expression
+    {
+    protected:
+        explicit literal(const struct position position);
+    };
+
     /**
      * Constant definition.
      */
     class constant_definition : public definition
     {
-        number_literal<std::int32_t> *m_body;
+        literal *m_body;
 
     public:
         /**
@@ -367,10 +373,10 @@ namespace source
          * \param body Constant value.
          */
         constant_definition(const struct position position, const std::string& identifier,
-                number_literal<std::int32_t> *body);
+                literal *body);
         virtual void accept(parser_visitor *visitor) override;
 
-        number_literal<std::int32_t>& body();
+        literal& body();
 
         virtual ~constant_definition() override;
     };
@@ -624,13 +630,13 @@ namespace source
     };
 
     template<typename T>
-    class number_literal : public expression
+    class number_literal : public literal
     {
         T m_number;
 
     public:
         number_literal(const struct position position, const T value)
-            : expression(position), m_number(value)
+            : literal(position), m_number(value)
         {
         }
 
@@ -645,18 +651,7 @@ namespace source
         }
     };
 
-    class char_literal : public expression
-    {
-        unsigned char m_character;
-
-    public:
-        char_literal(const struct position position, const unsigned char value);
-        virtual void accept(parser_visitor *visitor) override;
-
-        unsigned char character() const;
-    };
-
-    class string_literal : public expression
+    class string_literal : public literal
     {
         std::string m_string;
 
diff --git a/source/ast.cc b/source/ast.cc
index 015ed21..26d8480 100644
--- a/source/ast.cc
+++ b/source/ast.cc
@@ -146,7 +146,7 @@ namespace source
     {
     }
 
-    void empty_visitor::visit(char_literal *)
+    void empty_visitor::visit(number_literal<unsigned char> *)
     {
     }
 
@@ -376,7 +376,7 @@ namespace source
     }
 
     constant_definition::constant_definition(const struct position position, const std::string& identifier,
-            number_literal<std::int32_t> *body)
+            literal *body)
         : definition(position, identifier), m_body(body)
     {
     }
@@ -386,7 +386,7 @@ namespace source
         visitor->visit(this);
     }
 
-    number_literal<std::int32_t>& constant_definition::body()
+    literal& constant_definition::body()
     {
         return *m_body;
     }
@@ -493,23 +493,13 @@ namespace source
         }
     }
 
-    char_literal::char_literal(const struct position position, const unsigned char value)
-        : expression(position), m_character(value)
+    literal::literal(const struct position position)
+        : expression(position)
     {
     }
 
-    void char_literal::accept(parser_visitor *visitor)
-    {
-        visitor->visit(this);
-    }
-
-    unsigned char char_literal::character() const
-    {
-        return m_character;
-    }
-
     string_literal::string_literal(const struct position position, const std::string& value)
-        : expression(position), m_string(value)
+        : literal(position), m_string(value)
     {
     }
 
diff --git a/source/parser.yy b/source/parser.yy
index 6cf86b0..65db0aa 100644
--- a/source/parser.yy
+++ b/source/parser.yy
@@ -74,11 +74,7 @@
 %precedence THEN
 %precedence ELSE
 
-%type <elna::source::number_literal<std::int32_t> *> integer_literal;
-%type <elna::source::number_literal<double> *> float_literal;
-%type <elna::source::number_literal<bool> *> boolean_literal;
-%type <elna::source::char_literal *> character_literal;
-%type <elna::source::string_literal *> string_literal;
+%type <elna::source::literal *> literal;
 %type <elna::source::constant_definition *> constant_definition;
 %type <std::vector<elna::source::constant_definition *>> constant_part constant_definitions;
 %type <elna::source::variable_declaration *> variable_declaration;
@@ -165,26 +161,6 @@ procedure_definitions:
 procedure_part:
     /* no procedure definitions */ {}
     | procedure_definitions { std::swap($$, $1); }
-integer_literal: INTEGER
-        {
-            $$ = new elna::source::number_literal<std::int32_t>(elna::source::make_position(@1), $1); 
-        };
-float_literal: FLOAT
-        {
-            $$ = new elna::source::number_literal<double>(elna::source::make_position(@1), $1); 
-        };
-character_literal: CHARACTER
-        {
-            $$ = new elna::source::char_literal(elna::source::make_position(@1), $1.at(0)); 
-        };
-string_literal: STRING
-        {
-            $$ = new elna::source::string_literal(elna::source::make_position(@1), $1); 
-        };
-boolean_literal: BOOLEAN
-        {
-            $$ = new elna::source::number_literal<bool>(elna::source::make_position(@1), $1); 
-        };
 compound_statement: BEGIN_BLOCK optional_statements END_BLOCK
         {
             $$ = new elna::source::compound_statement(elna::source::make_position(@1));
@@ -215,12 +191,29 @@ if_statement:
             $$ = new elna::source::if_statement(elna::source::make_position(@1),
                 $2, $4, $6);
         }
+literal:
+    INTEGER
+        {
+            $$ = new elna::source::number_literal<std::int32_t>(elna::source::make_position(@1), $1);
+        }
+    | FLOAT
+        {
+            $$ = new elna::source::number_literal<double>(elna::source::make_position(@1), $1);
+        }
+    | BOOLEAN
+        {
+            $$ = new elna::source::number_literal<bool>(elna::source::make_position(@1), $1);
+        }
+    | CHARACTER
+        {
+            $$ = new elna::source::number_literal<unsigned char>(elna::source::make_position(@1), $1.at(0));
+        }
+    | STRING
+        {
+            $$ = new elna::source::string_literal(elna::source::make_position(@1), $1);
+        }
 pointer:
-    integer_literal { $$ = $1; }
-    | float_literal { $$ = $1; }
-    | boolean_literal { $$ = $1; }
-    | character_literal { $$ = $1; }
-    | string_literal { $$ = $1; }
+    literal { $$ = $1; }
     | designator_expression { $$ = $1; }
     | LEFT_PAREN expression RIGHT_PAREN { $$ = std::move($2); }
 summand:
@@ -359,7 +352,7 @@ type_expression:
         }
 variable_declaration: IDENTIFIER COLON type_expression
         {
-            $$ = new elna::source::variable_declaration(elna::source::make_position(@1), $1, $3); 
+            $$ = new elna::source::variable_declaration(elna::source::make_position(@1), $1, $3);
         };
 variable_declarations:
     variable_declaration COMMA variable_declarations
@@ -371,9 +364,9 @@ variable_declarations:
 variable_part:
     /* no variable declarations */ {}
     | VAR variable_declarations SEMICOLON { std::swap($$, $2); }
-constant_definition: IDENTIFIER EQUALS integer_literal
+constant_definition: IDENTIFIER EQUALS literal
         {
-            $$ = new elna::source::constant_definition(elna::source::make_position(@1), $1, $3); 
+            $$ = new elna::source::constant_definition(elna::source::make_position(@1), $1, $3);
         }
 constant_definitions:
     constant_definition COMMA constant_definitions