diff --git a/backend/riscv.cpp b/backend/riscv.cpp
index 604aa2b..2ce4b92 100644
--- a/backend/riscv.cpp
+++ b/backend/riscv.cpp
@@ -81,11 +81,112 @@ namespace elna::riscv
     {
     }
 
+    void visitor::generate_intrinsics()
+    {
+        this->writer->sink("printf");
+        {
+            auto format_string = this->writer->sink(reinterpret_cast<const std::byte *>("%c\n\0"), 4);
+
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::sp, funct3_t::addi, x_register::sp, -8));
+            this->instructions.push_back(instruction(base_opcode::store)
+                    .s(4, funct3_t::sw, x_register::sp, x_register::s0));
+            this->instructions.push_back(instruction(base_opcode::store)
+                    .s(0, funct3_t::sw, x_register::sp, x_register::ra));
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::s0, funct3_t::addi, x_register::sp, -8));
+
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::a1, funct3_t::addi, x_register::zero, 't'));
+            this->instructions.push_back(instruction(base_opcode::branch)
+                    .b(8, funct3_t::bne, x_register::zero, x_register::a0));
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::a1, funct3_t::addi, x_register::zero, 'f'));
+
+            relocate(format_string, address_t::high20);
+            this->instructions.push_back(instruction(base_opcode::lui).u(x_register::a5, 0));
+            relocate(format_string, address_t::lower12i);
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::a0, funct3_t::addi, x_register::a5, 0));
+
+            relocate("printf", address_t::text);
+            this->instructions.push_back(instruction(base_opcode::auipc).u(x_register::ra, 0));
+            this->instructions.push_back(instruction(base_opcode::jalr)
+                    .i(x_register::ra, funct3_t::jalr, x_register::ra, 0));
+
+            this->instructions.push_back(instruction(base_opcode::load)
+                    .i(x_register::s0, funct3_t::lw, x_register::sp, 4));
+            this->instructions.push_back(instruction(base_opcode::load)
+                    .i(x_register::ra, funct3_t::lw, x_register::sp, 0));
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::sp, funct3_t::addi, x_register::sp, 8));
+            this->instructions.push_back(instruction(base_opcode::jalr)
+                    .i(x_register::zero, funct3_t::jalr, x_register::ra, 0));
+
+            this->writer->sink("writeb", reinterpret_cast<const std::byte *>(this->instructions.data()),
+                    this->instructions.size() * sizeof(instruction));
+     
+            this->instructions.clear();
+        }
+        {
+            auto format_string = this->writer->sink(reinterpret_cast<const std::byte *>("%d\n\0"), 4);
+
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::sp, funct3_t::addi, x_register::sp, -8));
+            this->instructions.push_back(instruction(base_opcode::store)
+                    .s(4, funct3_t::sw, x_register::sp, x_register::s0));
+            this->instructions.push_back(instruction(base_opcode::store)
+                    .s(0, funct3_t::sw, x_register::sp, x_register::ra));
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::s0, funct3_t::addi, x_register::sp, -8));
+
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::a1, funct3_t::addi, x_register::a0, 0));
+
+            relocate(format_string, address_t::high20);
+            this->instructions.push_back(instruction(base_opcode::lui).u(x_register::a5, 0));
+            relocate(format_string, address_t::lower12i);
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::a0, funct3_t::addi, x_register::a5, 0));
+
+            relocate("printf", address_t::text);
+            this->instructions.push_back(instruction(base_opcode::auipc).u(x_register::ra, 0));
+            this->instructions.push_back(instruction(base_opcode::jalr)
+                    .i(x_register::ra, funct3_t::jalr, x_register::ra, 0));
+
+            this->instructions.push_back(instruction(base_opcode::load)
+                    .i(x_register::s0, funct3_t::lw, x_register::sp, 4));
+            this->instructions.push_back(instruction(base_opcode::load)
+                    .i(x_register::ra, funct3_t::lw, x_register::sp, 0));
+            this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(x_register::sp, funct3_t::addi, x_register::sp, 8));
+            this->instructions.push_back(instruction(base_opcode::jalr)
+                    .i(x_register::zero, funct3_t::jalr, x_register::ra, 0));
+
+            this->writer->sink("writei", reinterpret_cast<const std::byte *>(this->instructions.data()),
+                    this->instructions.size() * sizeof(instruction));
+     
+            this->instructions.clear();
+        }
+    }
+
+    void visitor::relocate(std::string_view name, address_t target)
+    {
+        this->references.push_back(reference());
+        this->references.back().name = name;
+        this->references.back().offset = writer->size() + instructions.size() * 4;
+        this->references.back().target = target;
+    }
+
     void visitor::visit(source::declaration *declaration)
     {
     }
 
-    void visitor::visit(source::definition *definition)
+    void visitor::visit(source::constant_definition *definition)
+    {
+    }
+
+    void visitor::visit(source::procedure_definition *definition)
     {
     }
 
@@ -126,51 +227,8 @@ namespace elna::riscv
 
     void visitor::visit(source::program *program)
     {
-        this->writer->sink("printf");
-        auto format_string = this->writer->sink(reinterpret_cast<const std::byte *>("%d\n\0"), 4);
+        generate_intrinsics();
 
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::sp, funct3_t::addi, x_register::sp, -8));
-        this->instructions.push_back(instruction(base_opcode::store)
-            .s(4, funct3_t::sw, x_register::sp, x_register::s0));
-        this->instructions.push_back(instruction(base_opcode::store)
-            .s(0, funct3_t::sw, x_register::sp, x_register::ra));
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::s0, funct3_t::addi, x_register::sp, -8));
-
-        this->references.push_back(reference());
-        this->references.back().name = format_string;
-        this->references.back().offset = writer->size() + instructions.size() * 4;
-        this->references.back().target = address_t::high20;
-        this->instructions.push_back(instruction(base_opcode::lui).u(x_register::a5, 0));
-        this->references.push_back(reference());
-        this->references.back().name = format_string;
-        this->references.back().offset = writer->size() + instructions.size() * 4;
-        this->references.back().target = address_t::lower12i;
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::a0, funct3_t::addi, x_register::a5, 0));
-
-        this->references.push_back(reference());
-        this->references.back().name = "printf";
-        this->references.back().offset = writer->size() + instructions.size() * 4;
-        this->references.back().target = address_t::text;
-        this->instructions.push_back(instruction(base_opcode::auipc).u(x_register::ra, 0));
-        this->instructions.push_back(instruction(base_opcode::jalr)
-            .i(x_register::ra, funct3_t::jalr, x_register::ra, 0));
-
-        this->instructions.push_back(instruction(base_opcode::load)
-            .i(x_register::s0, funct3_t::lw, x_register::sp, 4));
-        this->instructions.push_back(instruction(base_opcode::load)
-            .i(x_register::ra, funct3_t::lw, x_register::sp, 0));
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::sp, funct3_t::addi, x_register::sp, 8));
-        this->instructions.push_back(instruction(base_opcode::jalr)
-            .i(x_register::zero, funct3_t::jalr, x_register::ra, 0));
-
-        this->writer->sink("writei", reinterpret_cast<const std::byte *>(this->instructions.data()),
-                this->instructions.size() * sizeof(instruction));
- 
-        this->instructions.clear();
         visit(dynamic_cast<source::block *>(program));
         this->writer->sink("main", reinterpret_cast<const std::byte *>(this->instructions.data()),
                 this->instructions.size() * sizeof(instruction));
@@ -180,41 +238,7 @@ namespace elna::riscv
     {
         statement->arguments().accept(this);
 
-        // Print the result.
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::a1, funct3_t::addi, x_register::a0, 0));
-
-        this->instructions.push_back(instruction(base_opcode::auipc).u(x_register::ra, 0));
-        this->instructions.push_back(instruction(base_opcode::jalr)
-            .i(x_register::ra, funct3_t::jalr, x_register::ra, -instructions.size() * 4 - 40));
-    }
-
-    void visitor::visit(source::question_mark_statement *statement)
-    {
-        statement->body().accept(this);
-
-        // Print the result.
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::a1, funct3_t::addi, x_register::a0, 0));
-
-        auto format_string = this->writer->sink(reinterpret_cast<const std::byte *>("%d\n\0"), 4);
-
-        this->references.push_back(reference());
-        this->references.back().name = format_string;
-        this->references.back().offset = writer->size() + instructions.size() * 4;
-        this->references.back().target = address_t::high20;
-        this->instructions.push_back(instruction(base_opcode::lui).u(x_register::a5, 0));
-        this->references.push_back(reference());
-        this->references.back().name = format_string;
-        this->references.back().offset = writer->size() + instructions.size() * 4;
-        this->references.back().target = address_t::lower12i;
-
-        this->instructions.push_back(instruction(base_opcode::opImm)
-            .i(x_register::a0, funct3_t::addi, x_register::a5, 0));
-        this->references.push_back(reference());
-        this->references.back().name = "printf";
-        this->references.back().offset = writer->size() + instructions.size() * 4;
-        this->references.back().target = address_t::text;
+        relocate(statement->name(), address_t::text);
         this->instructions.push_back(instruction(base_opcode::auipc).u(x_register::ra, 0));
         this->instructions.push_back(instruction(base_opcode::jalr)
             .i(x_register::ra, funct3_t::jalr, x_register::ra, 0));
@@ -242,15 +266,15 @@ namespace elna::riscv
 
     void visitor::visit(source::if_statement *statement)
     {
-        const auto free_register = this->register_in_use ? x_register::a0 : x_register::t0;
-
         statement->prerequisite().accept(this);
 
+        const auto free_register = this->register_in_use ? x_register::a0 : x_register::t0;
+
         auto before_branch = instructions.size();
         instructions.push_back(instruction(base_opcode::branch));
         statement->body().accept(this);
         instructions[before_branch]
-            .b((instructions.size() - before_branch) * 4, funct3_t::beq, x_register::zero, free_register);
+            .b((instructions.size() - before_branch) * 4 - 4, funct3_t::beq, x_register::zero, free_register);
     }
 
     void visitor::visit(source::while_statement *statement)
diff --git a/backend/target.cpp b/backend/target.cpp
index da9ddf1..cd5375d 100644
--- a/backend/target.cpp
+++ b/backend/target.cpp
@@ -204,22 +204,19 @@ namespace elna::riscv
 
         for (auto& reference : _visitor.references)
         {
-            ELFIO::Elf_Word relocated_symbol{ 0 };
+            ELFIO::Elf_Word relocated_symbol = lookup(syma, reference.name);
 
             switch (reference.target)
             {
                 case address_t::high20:
-                    relocated_symbol = lookup(syma, reference.name);
                     rela.add_entry(reference.offset, relocated_symbol, 26 /* ELFIO::R_RISCV_HI20 */);
                     rela.add_entry(reference.offset, relocated_symbol, 51 /* ELFIO::R_RISCV_RELAX */);
                     break;
                 case address_t::lower12i:
-                    relocated_symbol = lookup(syma, reference.name);
                     rela.add_entry(reference.offset, relocated_symbol, 27 /* ELFIO::R_RISCV_LO12_I */);
                     rela.add_entry(reference.offset, relocated_symbol, 51 /* ELFIO::R_RISCV_RELAX */);
                     break;
                 case address_t::text:
-                    relocated_symbol = lookup(syma, "printf");
                     rela.add_entry(reference.offset, relocated_symbol, 18 /* ELFIO::R_RISCV_CALL */);
                     rela.add_entry(reference.offset, relocated_symbol, 51 /* ELFIO::R_RISCV_RELAX */);
                     break;
diff --git a/include/elna/backend/riscv.hpp b/include/elna/backend/riscv.hpp
index d67c3af..acb6ed8 100644
--- a/include/elna/backend/riscv.hpp
+++ b/include/elna/backend/riscv.hpp
@@ -160,10 +160,13 @@ namespace elna::riscv
     class visitor final : public source::parser_visitor
     {
         std::shared_ptr<source::writer> writer;
-
-    public:
         std::vector<instruction> instructions;
         bool register_in_use{ true };
+
+        void generate_intrinsics();
+        void relocate(std::string_view name, address_t target);
+
+    public:
         std::uint32_t variable_counter = 1;
         std::vector<reference> references;
         std::shared_ptr<source::symbol_table> table;
@@ -171,9 +174,9 @@ namespace elna::riscv
         visitor(std::shared_ptr<source::writer> writer);
 
         virtual void visit(source::declaration *declaration) override;
-        virtual void visit(source::definition *definition) override;
+        virtual void visit(source::constant_definition *definition) override;
+        virtual void visit(source::procedure_definition *definition) override;
         virtual void visit(source::call_statement *statement) override;
-        virtual void visit(source::question_mark_statement *statement) override;
         virtual void visit(source::compound_statement *statement) override;
         virtual void visit(source::assign_statement *statement) override;
         virtual void visit(source::if_statement *statement) override;
diff --git a/include/elna/source/lexer.hpp b/include/elna/source/lexer.hpp
index e250f6e..0e3ca3e 100644
--- a/include/elna/source/lexer.hpp
+++ b/include/elna/source/lexer.hpp
@@ -70,11 +70,11 @@ namespace elna::source
             end,
             assignment,
             colon,
-            question_mark,
             when,
             then,
             _while,
-            _do
+            _do,
+            procedure
         };
 
         /**
diff --git a/include/elna/source/parser.hpp b/include/elna/source/parser.hpp
index 615d52d..b3aef1e 100644
--- a/include/elna/source/parser.hpp
+++ b/include/elna/source/parser.hpp
@@ -15,9 +15,9 @@ namespace elna::source
     };
 
     class declaration;
-    class definition;
+    class constant_definition;
+    class procedure_definition;
     class call_statement;
-    class question_mark_statement;
     class compound_statement;
     class assign_statement;
     class if_statement;
@@ -32,9 +32,9 @@ namespace elna::source
     struct parser_visitor
     {
         virtual void visit(declaration *) = 0;
-        virtual void visit(definition *) = 0;
+        virtual void visit(constant_definition *) = 0;
+        virtual void visit(procedure_definition *) = 0;
         virtual void visit(call_statement *) = 0;
-        virtual void visit(question_mark_statement *) = 0;
         virtual void visit(compound_statement *) = 0;
         virtual void visit(assign_statement *) = 0;
         virtual void visit(if_statement *) = 0;
@@ -50,9 +50,9 @@ namespace elna::source
     struct empty_visitor : parser_visitor
     {
         virtual void visit(declaration *declaration) override;
-        virtual void visit(definition *definition) override;
+        virtual void visit(constant_definition *definition) override;
+        virtual void visit(procedure_definition *definition) override;
         virtual void visit(call_statement *statement) override;
-        virtual void visit(question_mark_statement *statement) override;
         virtual void visit(compound_statement *statement) override;
         virtual void visit(assign_statement *statement) override;
         virtual void visit(if_statement *) override;
@@ -82,10 +82,6 @@ namespace elna::source
     {
     };
 
-    class condition : public node
-    {
-    };
-
     /**
      * Variable declaration.
      */
@@ -106,16 +102,36 @@ namespace elna::source
     class definition : public node
     {
         std::string m_identifier;
+
+    protected:
+        definition(const std::string& identifier);
+
+    public:
+        std::string& identifier() noexcept;
+    };
+
+    class constant_definition : public definition
+    {
         std::unique_ptr<integer_literal> m_body;
 
     public:
-        definition(const std::string& identifier, std::unique_ptr<integer_literal>&& body);
+        constant_definition(const std::string& identifier, std::unique_ptr<integer_literal>&& body);
         virtual void accept(parser_visitor *visitor) override;
 
-        std::string& identifier() noexcept;
         integer_literal& body();
     };
 
+    class procedure_definition : public definition
+    {
+        std::unique_ptr<block> m_body;
+
+    public:
+        procedure_definition(const std::string& identifier, std::unique_ptr<block>&& body);
+        virtual void accept(parser_visitor *visitor) override;
+
+        block& body();
+    };
+
     class call_statement : public statement
     {
         std::string m_name;
@@ -129,17 +145,6 @@ namespace elna::source
         expression& arguments();
     };
 
-    class question_mark_statement : public statement
-    {
-        std::unique_ptr<condition> m_body;
-
-    public:
-        question_mark_statement(std::unique_ptr<condition>&& body);
-        virtual void accept(parser_visitor *visitor) override;
-
-        condition& body();
-    };
-
     class compound_statement : public statement
     {
         std::vector<std::unique_ptr<statement>> m_statements;
@@ -167,27 +172,27 @@ namespace elna::source
 
     class if_statement : public statement
     {
-        std::unique_ptr<condition> m_prerequisite;
+        std::unique_ptr<expression> m_prerequisite;
         std::unique_ptr<statement> m_body;
 
     public:
-        if_statement(std::unique_ptr<condition>&& prerequisite, std::unique_ptr<statement>&& body);
+        if_statement(std::unique_ptr<expression>&& prerequisite, std::unique_ptr<statement>&& body);
         virtual void accept(parser_visitor *visitor) override;
 
-        condition& prerequisite();
+        expression& prerequisite();
         statement& body();
     };
 
     class while_statement : public statement
     {
-        std::unique_ptr<condition> m_prerequisite;
+        std::unique_ptr<expression> m_prerequisite;
         std::unique_ptr<statement> m_body;
 
     public:
-        while_statement(std::unique_ptr<condition>&& prerequisite, std::unique_ptr<statement>&& body);
+        while_statement(std::unique_ptr<expression>&& prerequisite, std::unique_ptr<statement>&& body);
         virtual void accept(parser_visitor *visitor) override;
 
-        condition& prerequisite();
+        expression& prerequisite();
         statement& body();
     };
 
@@ -230,7 +235,7 @@ namespace elna::source
         std::int32_t number() const noexcept;
     };
 
-    class boolean_literal : public condition
+    class boolean_literal : public expression
     {
         bool m_boolean;
 
@@ -273,12 +278,10 @@ namespace elna::source
         std::unique_ptr<expression> parse_factor();
         std::unique_ptr<expression> parse_term();
         std::unique_ptr<expression> parse_expression();
-        std::unique_ptr<condition> parse_condition();
-        std::unique_ptr<definition> parse_definition();
+        std::unique_ptr<constant_definition> parse_constant_definition();
         std::unique_ptr<declaration> parse_declaration();
         std::unique_ptr<statement> parse_statement();
         std::unique_ptr<call_statement> parse_call_statement();
-        std::unique_ptr<question_mark_statement> parse_question_mark_statement();
         std::unique_ptr<compound_statement> parse_compound_statement();
         std::unique_ptr<assign_statement> parse_assign_statement();
         std::unique_ptr<if_statement> parse_if_statement();
diff --git a/include/elna/source/semantic.hpp b/include/elna/source/semantic.hpp
index 6d2e311..5022814 100644
--- a/include/elna/source/semantic.hpp
+++ b/include/elna/source/semantic.hpp
@@ -9,7 +9,7 @@ namespace elna::source
         std::shared_ptr<symbol_table> table;
 
     public:
-        void visit(definition *definition) override;
+        void visit(constant_definition *definition) override;
         void visit(declaration *declaration) override;
         void visit(block *block) override;
     };
diff --git a/source/lexer.cpp b/source/lexer.cpp
index a1f7b6b..1382259 100644
--- a/source/lexer.cpp
+++ b/source/lexer.cpp
@@ -350,10 +350,6 @@ namespace elna::source
             {
                 tokens.emplace_back(token::type::comma, iterator.position());
             }
-            else if (*iterator == '?')
-            {
-                tokens.emplace_back(token::type::question_mark, iterator.position());
-            }
             else if (*iterator == '.')
             {
                 tokens.emplace_back(token::type::dot, iterator.position());
@@ -407,6 +403,10 @@ namespace elna::source
                 {
                     tokens.emplace_back(token::type::boolean, 0, iterator.position());
                 }
+                else if (word == "proc")
+                {
+                    tokens.emplace_back(token::type::procedure, 0, iterator.position());
+                }
                 else
                 {
                     tokens.emplace_back(token::type::identifier, word.c_str(), iterator.position());
diff --git a/source/parser.cpp b/source/parser.cpp
index fadf5e1..e0dc3c3 100644
--- a/source/parser.cpp
+++ b/source/parser.cpp
@@ -7,7 +7,12 @@ namespace elna::source
     {
     }
 
-    void empty_visitor::visit(definition *definition)
+    void empty_visitor::visit(constant_definition *definition)
+    {
+        definition->body().accept(this);
+    }
+
+    void empty_visitor::visit(procedure_definition *definition)
     {
         definition->body().accept(this);
     }
@@ -17,11 +22,6 @@ namespace elna::source
         statement->arguments().accept(this);
     }
 
-    void empty_visitor::visit(question_mark_statement *statement)
-    {
-        statement->body().accept(this);
-    }
-
     void empty_visitor::visit(compound_statement *statement)
     {
         for (auto& nested_statement : statement->statements())
@@ -95,24 +95,19 @@ namespace elna::source
     {
     }
 
-    std::string& declaration::identifier() noexcept
-    {
-        return m_identifier;
-    }
-
-    definition::definition(const std::string& identifier, std::unique_ptr<integer_literal>&& body)
-        : m_identifier(std::move(identifier)), m_body(std::move(body))
-    {
-    }
-
     void declaration::accept(parser_visitor *visitor)
     {
         visitor->visit(this);
     }
 
-    void definition::accept(parser_visitor *visitor)
+    std::string& declaration::identifier() noexcept
+    {
+        return m_identifier;
+    }
+
+    definition::definition(const std::string& identifier)
+        : m_identifier(identifier)
     {
-        visitor->visit(this);
     }
 
     std::string& definition::identifier() noexcept
@@ -120,7 +115,32 @@ namespace elna::source
         return m_identifier;
     }
 
-    integer_literal& definition::body()
+    constant_definition::constant_definition(const std::string& identifier, std::unique_ptr<integer_literal>&& body)
+        : definition(identifier), m_body(std::move(body))
+    {
+    }
+
+    void constant_definition::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
+    }
+
+    integer_literal& constant_definition::body()
+    {
+        return *m_body;
+    }
+
+    procedure_definition::procedure_definition(const std::string& identifier, std::unique_ptr<block>&& body)
+        : definition(identifier), m_body(std::move(body))
+    {
+    }
+
+    void procedure_definition::accept(parser_visitor *visitor)
+    {
+        visitor->visit(this);
+    }
+
+    block& procedure_definition::body()
     {
         return *m_body;
     }
@@ -279,21 +299,6 @@ namespace elna::source
         return *m_body;
     }
 
-    question_mark_statement::question_mark_statement(std::unique_ptr<condition>&& body)
-        : m_body(std::move(body))
-    {
-    }
-
-    void question_mark_statement::accept(parser_visitor *visitor)
-    {
-        visitor->visit(this);
-    }
-
-    condition& question_mark_statement::body()
-    {
-        return *m_body;
-    }
-
     compound_statement::compound_statement(std::vector<std::unique_ptr<statement>>&& statements)
         : m_statements(std::move(statements))
     {
@@ -329,7 +334,7 @@ namespace elna::source
         return *m_rvalue;
     }
 
-    if_statement::if_statement(std::unique_ptr<condition>&& prerequisite, std::unique_ptr<statement>&& body)
+    if_statement::if_statement(std::unique_ptr<expression>&& prerequisite, std::unique_ptr<statement>&& body)
         : m_prerequisite(std::move(prerequisite)), m_body(std::move(body))
     {
     }
@@ -339,7 +344,7 @@ namespace elna::source
         visitor->visit(this);
     }
 
-    condition& if_statement::prerequisite()
+    expression& if_statement::prerequisite()
     {
         return *m_prerequisite;
     }
@@ -349,7 +354,7 @@ namespace elna::source
         return *m_body;
     }
 
-    while_statement::while_statement(std::unique_ptr<condition>&& prerequisite, std::unique_ptr<statement>&& body)
+    while_statement::while_statement(std::unique_ptr<expression>&& prerequisite, std::unique_ptr<statement>&& body)
         : m_prerequisite(std::move(prerequisite)), m_body(std::move(body))
     {
     }
@@ -359,7 +364,7 @@ namespace elna::source
         visitor->visit(this);
     }
 
-    condition& while_statement::prerequisite()
+    expression& while_statement::prerequisite()
     {
         return *m_prerequisite;
     }
@@ -407,6 +412,12 @@ namespace elna::source
             ++iterator;
             return result;
         }
+        else if (iterator->of() == source::token::token::type::boolean)
+        {
+            auto result = std::make_unique<boolean_literal>(iterator->number());
+            ++iterator;
+            return result;
+        }
         else if (iterator->of() == source::token::type::left_paren)
         {
             ++iterator;
@@ -458,18 +469,7 @@ namespace elna::source
         return term;
     }
 
-    std::unique_ptr<condition> parser::parse_condition()
-    {
-        if (iterator->of() == source::token::token::type::boolean)
-        {
-            auto result = std::make_unique<boolean_literal>(iterator->number());
-            ++iterator;
-            return result;
-         }
-        return nullptr;
-    }
-
-    std::unique_ptr<definition> parser::parse_definition()
+    std::unique_ptr<constant_definition> parser::parse_constant_definition()
     {
         auto definition_identifier = iterator.advance(token::type::identifier);
 
@@ -484,7 +484,7 @@ namespace elna::source
 
         if (iterator->of() == source::token::type::number)
         {
-            auto result = std::make_unique<definition>(definition_identifier.value().get().identifier(),
+            auto result = std::make_unique<constant_definition>(definition_identifier.value().get().identifier(),
                     std::make_unique<integer_literal>(iterator->number()));
             ++iterator;
             return result;
@@ -519,10 +519,6 @@ namespace elna::source
         {
             return parse_call_statement();
         }
-        else if (iterator.current(token::type::question_mark))
-        {
-            return parse_question_mark_statement();
-        }
         else if (iterator.current(token::type::begin))
         {
             return parse_compound_statement();
@@ -555,21 +551,6 @@ namespace elna::source
         return nullptr;
     }
 
-    std::unique_ptr<question_mark_statement> parser::parse_question_mark_statement()
-    {
-        if (!iterator.advance(token::type::question_mark))
-        {
-            return nullptr;
-        }
-        auto question_mark_body = parse_condition();
-
-        if (question_mark_body != nullptr)
-        {
-            return std::make_unique<question_mark_statement>(std::move(question_mark_body));
-        }
-        return nullptr;
-    }
-
     std::unique_ptr<compound_statement> parser::parse_compound_statement()
     {
         if (!iterator.advance(token::type::begin))
@@ -624,7 +605,7 @@ namespace elna::source
         {
             return nullptr;
         }
-        auto condition = parse_condition();
+        auto condition = parse_expression();
 
         if (condition == nullptr || !iterator.skip(token::type::then))
         {
@@ -645,7 +626,7 @@ namespace elna::source
         {
             return nullptr;
         }
-        auto condition = parse_condition();
+        auto condition = parse_expression();
 
         if (condition == nullptr || !iterator.skip(token::type::_do))
         {
@@ -671,7 +652,7 @@ namespace elna::source
         ++iterator; // Skip const.
 
         std::unique_ptr<definition> parsed_definition;
-        while ((parsed_definition = parse_definition()) != nullptr)
+        while ((parsed_definition = parse_constant_definition()) != nullptr)
         {
             definitions.push_back(std::move(parsed_definition));
 
diff --git a/source/semantic.cpp b/source/semantic.cpp
index bd0eb94..7d3660a 100644
--- a/source/semantic.cpp
+++ b/source/semantic.cpp
@@ -3,7 +3,7 @@
 
 namespace elna::source
 {
-    void name_analysis_visitor::visit(definition *definition)
+    void name_analysis_visitor::visit(constant_definition *definition)
     {
         this->table->enter(definition->identifier(),
                 std::make_shared<constant_info>(constant_info(definition->body().number())));
diff --git a/tests/expectations/print_boolean.txt b/tests/expectations/print_boolean.txt
index b261da1..532e7b0 100644
--- a/tests/expectations/print_boolean.txt
+++ b/tests/expectations/print_boolean.txt
@@ -1,2 +1,2 @@
-1
-0
+t
+f
diff --git a/tests/print_boolean.eln b/tests/print_boolean.eln
index bc71153..7b24a1e 100644
--- a/tests/print_boolean.eln
+++ b/tests/print_boolean.eln
@@ -1,4 +1,4 @@
 begin
-  ? True;
-  ? False
+  writeb(True);
+  writeb(False)
 end.
diff --git a/tests/subtraction.eln b/tests/subtraction.eln
index cfad17e..05c22fc 100644
--- a/tests/subtraction.eln
+++ b/tests/subtraction.eln
@@ -1,2 +1,2 @@
-write(5 - 4)
+writei(5 - 4)
 .
diff --git a/tests/tester.cpp b/tests/tester.cpp
index 2c54ade..9538da4 100755
--- a/tests/tester.cpp
+++ b/tests/tester.cpp
@@ -114,9 +114,8 @@ namespace elna
 
         boost::asio::io_service io_service;
         std::future<std::string> buffer;
-        boost::process::child spike(
-            "/opt/riscv/bin/spike", "--isa=RV32IMAC",
-            "/opt/riscv/riscv32-unknown-elf/bin/pk",
+        boost::process::child qemu(
+            boost::process::search_path("qemu-riscv32"),
             test_binary.string(),
             boost::process::std_out > buffer,
             boost::process::std_err > buffer,
@@ -124,7 +123,7 @@ namespace elna
         );
         io_service.run();
 
-        return test_result{ test_status::successful, spike.exit_code(), buffer.get() };
+        return test_result{ test_status::successful, qemu.exit_code(), buffer.get() };
     }
 
     static test_results run_in_path(const std::filesystem::path test_directory)