diff --git a/design.md b/README.md
similarity index 87%
rename from design.md
rename to README.md
index 4dd9ecd..e1e63bd 100644
--- a/design.md
+++ b/README.md
@@ -53,6 +53,10 @@ All symbols are reserved keywords and can therefore NOT be used as labels.
 
 ## Symbols
 
+## Directives
+
+- `DECLARE` declares the first label argument to equal the second, immediate value, argument and is used to declare a constant for the virtual machine.
+
 ### Operands
 
 - `addi` add the first to the second argument and store the result in the third argument
@@ -71,6 +75,11 @@ All symbols are reserved keywords and can therefore NOT be used as labels.
 - `gti` execute next statement if argument 1 is greater than argument 2 else skip the next statement
 - `eqi` execute the next statement if argument 1 is equal to argument 2 else skip the next statement
 
+## Memory
+
+- `popi` pops the first value on the stack into the register specified as the first argument
+- `pushi` pushes the value on the stack from the register or immediate value as the first argument
+
 ## Interupts
 
 - 0..9 range:
diff --git a/bin/example.wasm b/bin/example.wasm
index fd1c3c9..0d4a369 100644
--- a/bin/example.wasm
+++ b/bin/example.wasm
@@ -1,3 +1,5 @@
+DECLARE MEMORY_SIZE $4096;
+
 addi $10 $-5 %A;
 subi %A $2 %B;
 muli $2 %B %C;
@@ -7,7 +9,7 @@ divi $2 %C %D;
 seti %A $0;
 
 # Loop from 0 to 10
-loop:
+count_loop:
 addi $1 %A %A;
 
 # Print the current value
@@ -18,7 +20,7 @@ int $0;
 seti %A %B;
 
 lti %A $10;
-jmp loop;
+jmp count_loop;
 
 # Hello world
 seti %A $72;  # H
@@ -31,5 +33,24 @@ int $0;
 seti %A $111; # o
 int $0;
 
+seti %A $32; # space
+int $0;
+
+pushi $68; # D
+pushi $76; # L
+pushi $82; # R
+pushi $79; # O 
+pushi $87; # W
+
+seti %B $5;
+
+world_loop:
+popi %A;
+int $0;
+
+subi %B $1 %B;
+gti %B $0;
+jmp world_loop;
+
 seti %A $10; # newline
 int $0;
\ No newline at end of file
diff --git a/include/execute/error.hpp b/include/execute/error.hpp
new file mode 100644
index 0000000..cfc305e
--- /dev/null
+++ b/include/execute/error.hpp
@@ -0,0 +1,19 @@
+#pragma once
+
+namespace Execute
+{
+	struct RuntimeError
+	{
+
+	};
+
+	struct StackUnderflow : RuntimeError
+	{
+
+	};
+
+	struct StackOverflow : RuntimeError
+	{
+
+	};
+}
\ No newline at end of file
diff --git a/include/execute/state.hpp b/include/execute/state.hpp
index 7c82b29..955bc0d 100644
--- a/include/execute/state.hpp
+++ b/include/execute/state.hpp
@@ -11,7 +11,9 @@ namespace Execute
 		unsigned nextStatement;
 		std::unordered_map<std::string, unsigned> const & labelStatementIndice;
 		std::vector<InterruptFn> const interrupts;
+		std::vector<std::uint8_t> memory;
+		unsigned stackPointer;
 
-		State(std::unordered_map<std::string, unsigned> const & labelStatementIndice);
+		State(std::unordered_map<std::string, unsigned> const & labelStatementIndice, unsigned const memorySize);
 	};
 }
\ No newline at end of file
diff --git a/include/execute/virtualmachine.hpp b/include/execute/virtualmachine.hpp
index a55f428..68a590f 100644
--- a/include/execute/virtualmachine.hpp
+++ b/include/execute/virtualmachine.hpp
@@ -17,6 +17,8 @@ namespace Execute
 
 		void Step();
 
+		VirtualMachine(Interpret::Code const & code, unsigned const memorySize);
+
 	public:
 		void Run();
 		void SingleStep();
@@ -28,6 +30,6 @@ namespace Execute
 		
 		bool IsTerminated() const;
 
-		VirtualMachine(Interpret::Code const & code);
+		static VirtualMachine CreateFromCode(Interpret::Code const & code);
 	};
 }
\ No newline at end of file
diff --git a/include/interpret/code.hpp b/include/interpret/code.hpp
index d319dd6..cc5e525 100644
--- a/include/interpret/code.hpp
+++ b/include/interpret/code.hpp
@@ -11,5 +11,6 @@ namespace Interpret
 	{
 		std::vector<std::unique_ptr<Statement>> statements;
 		std::unordered_map<std::string, unsigned> labelStatementIndice;
+		std::unordered_map<std::string, int> declarations;
 	};
 }
\ No newline at end of file
diff --git a/include/interpret/operanddefinitions.hpp b/include/interpret/operanddefinitions.hpp
index eee1f33..348a20d 100644
--- a/include/interpret/operanddefinitions.hpp
+++ b/include/interpret/operanddefinitions.hpp
@@ -7,5 +7,7 @@ namespace Interpret
 {
 	std::unique_ptr<Statement> ExtractStatement(unsigned const operatorIndex, std::vector<Token::Token> const & tokens);
 
+	std::tuple<std::string, int> ExtractDeclaration(unsigned const operatorIndex, std::vector<Token::Token> const & tokens);
+
 	int GetRequiredNumberOfArguments(Token::OperandType const type);
 }
\ No newline at end of file
diff --git a/include/interpret/statement.hpp b/include/interpret/statement.hpp
index fbad40c..799da5d 100644
--- a/include/interpret/statement.hpp
+++ b/include/interpret/statement.hpp
@@ -69,4 +69,18 @@ namespace Interpret
 
 		void Execute(Execute::Flags & flags, Execute::State & state, Execute::Registers & registers) override;
 	};
+
+	struct PushStatement : Statement
+	{
+		Value firstArgument;
+
+		void Execute(Execute::Flags & flags, Execute::State & state, Execute::Registers & registers) override;
+	};
+
+	struct PopStatement : Statement
+	{
+		Value firstArgument;
+
+		void Execute(Execute::Flags & flags, Execute::State & state, Execute::Registers & registers) override;
+	};
 }
\ No newline at end of file
diff --git a/include/token/operandtype.hpp b/include/token/operandtype.hpp
index da1b903..308b0dd 100644
--- a/include/token/operandtype.hpp
+++ b/include/token/operandtype.hpp
@@ -17,7 +17,10 @@ namespace Token
 		GreaterThanInteger,
 		EqualInteger,
 		SetInteger,
-		Interrupt
+		Interrupt,
+		Declaration,
+		PushInteger,
+		PopInteger
 	};
 
 	OperandType GetOperandType(std::string const & op);
diff --git a/src/execute/error.cpp b/src/execute/error.cpp
new file mode 100644
index 0000000..e83a30a
--- /dev/null
+++ b/src/execute/error.cpp
@@ -0,0 +1,6 @@
+#include <execute/error.hpp>
+
+namespace Execute
+{
+	
+}
\ No newline at end of file
diff --git a/src/execute/state.cpp b/src/execute/state.cpp
index 5969c41..164a621 100644
--- a/src/execute/state.cpp
+++ b/src/execute/state.cpp
@@ -2,11 +2,13 @@
 
 namespace Execute
 {
-	State::State(std::unordered_map<std::string, unsigned> const & _labelStatementIndice)
+	State::State(std::unordered_map<std::string, unsigned> const & _labelStatementIndice, unsigned const memorySize)
 		: currentStatement(0u),
 		nextStatement(1u),
 		labelStatementIndice(_labelStatementIndice),
-		interrupts(GetInterrupts())
+		interrupts(GetInterrupts()),
+		memory(memorySize),
+		stackPointer(0u)
 	{
 	}
 }
\ No newline at end of file
diff --git a/src/execute/virtualmachine.cpp b/src/execute/virtualmachine.cpp
index 3bf8d04..99d8d45 100644
--- a/src/execute/virtualmachine.cpp
+++ b/src/execute/virtualmachine.cpp
@@ -15,6 +15,15 @@ namespace Execute
 		}
 	}
 
+	VirtualMachine::VirtualMachine(Interpret::Code const & _code, unsigned const memorySize)
+		: flags(),
+		registers(),
+		state(_code.labelStatementIndice, memorySize),
+		terminated(false),
+		code(_code)
+	{
+	}
+
 	void VirtualMachine::Run()
 	{
 		while(!IsTerminated())
@@ -41,12 +50,16 @@ namespace Execute
 
 	bool VirtualMachine::IsTerminated() const { return terminated; } 
 
-	VirtualMachine::VirtualMachine(Interpret::Code const & _code)
-		: flags(),
-		registers(),
-		state(_code.labelStatementIndice),
-		terminated(false),
-		code(_code)
+	VirtualMachine VirtualMachine::CreateFromCode(Interpret::Code const & code)
 	{
+		unsigned memorySize = 1024;
+		auto const & userMemorySizeDeclared = code.declarations.find("MEMORY_SIZE");
+		if (userMemorySizeDeclared != code.declarations.end() && userMemorySizeDeclared->second >= 0)
+		{
+			memorySize = userMemorySizeDeclared->second;
+		}
+
+		std::printf("Creating Wassembly virtual machine with %u bytes of memory.\n", memorySize);
+		return VirtualMachine(code, memorySize);
 	}
 }
\ No newline at end of file
diff --git a/src/interpret/interpreter.cpp b/src/interpret/interpreter.cpp
index 5e5e56b..960f4e1 100644
--- a/src/interpret/interpreter.cpp
+++ b/src/interpret/interpreter.cpp
@@ -67,7 +67,19 @@ namespace Interpret
 				}
 				else
 				{
-					code.statements.emplace_back(ExtractStatement(operatorTokenIndex, tokens));
+					switch(std::get<Token::OperandType>(tokens[operatorTokenIndex].data))
+					{
+						case Token::OperandType::Declaration:
+						{
+							auto const tuple = ExtractDeclaration(operatorTokenIndex, tokens);
+							code.declarations[std::get<0>(tuple)] = std::get<1>(tuple);
+						}
+						break;
+
+						default:
+						code.statements.emplace_back(ExtractStatement(operatorTokenIndex, tokens));
+						break;
+					}
 					state = InterpreterState::FindOperand;
 				}
 				break;
diff --git a/src/interpret/operanddefinitions.cpp b/src/interpret/operanddefinitions.cpp
index 1d2005b..5fa2849 100644
--- a/src/interpret/operanddefinitions.cpp
+++ b/src/interpret/operanddefinitions.cpp
@@ -210,6 +210,22 @@ namespace Interpret
 				return statement;
 			}
 
+			case Token::OperandType::PopInteger:
+			{
+				auto statement = std::make_unique<PopStatement>();
+				statement->firstArgument = GetRegisterArgument(operandIndex + 1u, tokens);
+
+				return statement;
+			}
+
+			case Token::OperandType::PushInteger:
+			{
+				auto statement = std::make_unique<PushStatement>();
+				statement->firstArgument = GetImmediateOrRegisterArgument(operandIndex + 1u, tokens);
+
+				return statement;
+			}
+
 			default:
 			{
 				auto statement = std::make_unique<NoArgumentStatement>();
@@ -221,6 +237,22 @@ namespace Interpret
 		}
 	}
 
+	std::tuple<std::string, int> ExtractDeclaration(unsigned const operatorIndex, std::vector<Token::Token> const & tokens)
+	{
+		if (tokens[operatorIndex + 1u].type != Token::TokenType::Label)
+		{
+			throw ExpectedLabel(tokens[operatorIndex + 1u]);
+		}
+		if (tokens[operatorIndex + 2u].type != Token::TokenType::ImmediateInteger)
+		{
+			throw ExpectedImmediate(tokens[operatorIndex + 2u]);
+		}
+
+		auto const label = std::get<std::string>(tokens[operatorIndex + 1u].data);
+		auto const value = std::get<int>(tokens[operatorIndex + 2u].data);
+		return std::make_tuple(label, value);
+	}
+
 	int GetRequiredNumberOfArguments(Token::OperandType const type)
 	{
 		switch (type)
@@ -237,10 +269,13 @@ namespace Interpret
 			case Token::OperandType::GreaterThanInteger:
 			case Token::OperandType::EqualInteger:
 			case Token::OperandType::SetInteger:
+			case Token::OperandType::Declaration:
 			return 2;
 
 			case Token::OperandType::Jump:
 			case Token::OperandType::Interrupt:
+			case Token::OperandType::PushInteger:
+			case Token::OperandType::PopInteger:
 			return 1;
 
 			default:
diff --git a/src/interpret/statement.cpp b/src/interpret/statement.cpp
index ca68c4a..91ff4b9 100644
--- a/src/interpret/statement.cpp
+++ b/src/interpret/statement.cpp
@@ -1,3 +1,4 @@
+#include <execute/error.hpp>
 #include <interpret/statement.hpp>
 
 namespace Interpret
@@ -49,4 +50,29 @@ namespace Interpret
 	{
 		state.interrupts[firstArgument.GetValue(registers)](registers);
 	}
+
+	void PopStatement::Execute(Execute::Flags & flags, Execute::State & state, Execute::Registers & registers)
+	{
+		if (state.stackPointer < sizeof(int))
+		{
+			throw Execute::StackUnderflow();
+		}
+
+		auto const value = *(reinterpret_cast<int const *>(state.memory.data() + (state.stackPointer - 1u)));
+		firstArgument.GetValue(registers) = value;
+
+		state.stackPointer -= sizeof(int);
+	}
+
+	void PushStatement::Execute(Execute::Flags & flags, Execute::State & state, Execute::Registers & registers)
+	{
+		if ((state.memory.size() - state.stackPointer) < sizeof(int))
+		{
+			throw Execute::StackOverflow();
+		}
+
+		*(reinterpret_cast<int *>(state.memory.data() + state.stackPointer + (sizeof(int) - 1))) = firstArgument.GetValue(registers);
+
+		state.stackPointer += sizeof(int);
+	}
 }
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 39f474c..738b335 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -24,35 +24,8 @@ void PrintTokenError(Interpret::TokenError const & err, std::vector<std::string>
 	PrintBadToken(err.errorToken, lines);
 }
 
-int main(int argc, char ** argv)
+void PrintTokens(std::vector<Token::Token> const & tokens)
 {
-	if (argc != 2)
-	{
-		std::puts("Usage: wassembly [filename.wasm]");
-		return 1;
-	}
-
-	std::ifstream input(argv[1]);
-	if (!input.is_open())
-	{
-		std::printf("Error: Cannot open file %s for reading", argv[1]);
-		return 1;
-	}
-
-	std::vector<Token::Token> tokens;
-	Token::Tokenizer tokenizer;
-	std::vector<std::string> lines; // DEBUG
-	std::string line;
-	unsigned lineNumber = 0;
-	while(std::getline(input, line))
-	{
-		tokenizer.Tokenize(line, lineNumber, tokens);
-		++lineNumber;
-		lines.push_back(line); // DEBUG
-	}
-	input.close();
-
-	// DEBUG
 	std::puts("*** Tokenization result ***");
 	unsigned statementNumber = 0u;
 	std::printf("%02u - ", statementNumber);
@@ -73,7 +46,38 @@ int main(int argc, char ** argv)
 			}
 		}
 	}
-	// END DEBUG
+}
+
+void PrintLabels(Interpret::Code const & code)
+{
+	std::puts("\n*** Labels ***");
+	for(auto const & labelIndice : code.labelStatementIndice)
+	{
+		std::printf("Label %s points to statement %u\n", labelIndice.first.c_str(), labelIndice.second);
+	}
+}
+
+Interpret::Code GetCodeFromFile(std::string const & filePath)
+{
+	std::ifstream input(filePath);
+	if (!input.is_open())
+	{
+		std::printf("Error: Cannot open file %s for reading", filePath.c_str());
+		exit(1);
+	}
+
+	std::vector<Token::Token> tokens;
+	Token::Tokenizer tokenizer;
+	std::vector<std::string> lines;
+	std::string line;
+	unsigned lineNumber = 0;
+	while(std::getline(input, line))
+	{
+		tokenizer.Tokenize(line, lineNumber, tokens);
+		++lineNumber;
+		lines.push_back(line);
+	}
+	input.close();
 
 	// Validate the syntax
 	bool syntaxOk = true;
@@ -90,7 +94,7 @@ int main(int argc, char ** argv)
 	if (!syntaxOk)
 	{
 		std::puts("Aborting due to syntax error(s)");
-		return 1;
+		exit(1);
 	}
 
 	Interpret::Interpreter interpreter;
@@ -102,33 +106,23 @@ int main(int argc, char ** argv)
 	catch(Interpret::TokenError & e)
 	{
 		PrintTokenError(e, lines);
+		exit(1);
+	}
+
+	return code;
+}
+
+int main(int argc, char ** argv)
+{
+	if (argc != 2)
+	{
+		std::puts("Usage: wassembly [filename.wasm]");
 		return 1;
 	}
 
-	// DEBUG
-	std::puts("\n*** Labels ***");
-	for(auto const & labelIndice : code.labelStatementIndice)
-	{
-		std::printf("Label %s points to statement %u\n", labelIndice.first.c_str(), labelIndice.second);
-	}
-
-	std::puts("\n*** Execution ***");
-	Execute::VirtualMachine vm(code);
+	auto const code = GetCodeFromFile(argv[1]);
+	auto vm = Execute::VirtualMachine::CreateFromCode(code);
 	vm.Run();
-	/*
-	while(!vm.IsTerminated())
-	{
-		vm.SingleStep();
-		auto const & registers = vm.GetRegisters();
-		std::printf("A=%i B=%i C=%i D=%i\n", registers.A, registers.B, registers.C, registers.D);
-		auto const & state = vm.GetState();
-		std::printf("current_statement=%i\n", state.currentStatement);
-
-		std::puts("Press any key to step...");
-		std::getchar();
-	}
-	*/
-	// END DEBUG
 	
 	return 0;
 }
\ No newline at end of file
diff --git a/src/token/operandtype.cpp b/src/token/operandtype.cpp
index be20d00..ce16c68 100644
--- a/src/token/operandtype.cpp
+++ b/src/token/operandtype.cpp
@@ -18,7 +18,10 @@ namespace Token
 			{ "gti", OperandType::GreaterThanInteger },
 			{ "eqi", OperandType::EqualInteger },
 			{ "seti", OperandType::SetInteger },
-			{ "int", OperandType::Interrupt }
+			{ "int", OperandType::Interrupt },
+			{ "DECLARE", OperandType::Declaration },
+			{ "pushi", OperandType::PushInteger},
+			{ "popi", OperandType::PopInteger},
 		};
 
 		auto const & result = operations.find(op);