diff --git a/bin/app.php b/bin/app.php
index 97c362a..c024861 100644
--- a/bin/app.php
+++ b/bin/app.php
@@ -1,14 +1,16 @@
 <?php
 
 use Automata\Machine;
-use Automata\Tool;
+use Automata\ToolData;
 
 require_once __DIR__ . '/../vendor/autoload.php';
 
 $machine = new Machine();
-$machine->toolMemory->save(new Tool(1, 5500, 2));
-$machine->toolMemory->save(new Tool(2, 3000, 61379));
+$machine->TM->write(new ToolData(1, 5500, 2));
+$machine->TM->write(new ToolData(2, 3000, 61379));
 (new ProgramLoader)->loadPrograms($machine);
 
 $machine->loadProgram(9002);
-$machine->start();
+while ($machine->PPMC->ready()) {
+	$machine->step();
+}
diff --git a/ref/block_structure.jpeg b/ref/block_structure.jpeg
new file mode 100644
index 0000000..eb8f887
Binary files /dev/null and b/ref/block_structure.jpeg differ
diff --git a/ref/program_code_1.jpeg b/ref/program_code_1.jpeg
new file mode 100644
index 0000000..f5ea274
Binary files /dev/null and b/ref/program_code_1.jpeg differ
diff --git a/ref/program_code_2.jpeg b/ref/program_code_2.jpeg
new file mode 100644
index 0000000..5fbde8f
Binary files /dev/null and b/ref/program_code_2.jpeg differ
diff --git a/ref/program_code_3.jpeg b/ref/program_code_3.jpeg
new file mode 100644
index 0000000..08386ca
Binary files /dev/null and b/ref/program_code_3.jpeg differ
diff --git a/ref/programmable_words.jpeg b/ref/programmable_words.jpeg
new file mode 100644
index 0000000..9c771f9
Binary files /dev/null and b/ref/programmable_words.jpeg differ
diff --git a/ref/spindle_speeds.jpeg b/ref/spindle_speeds.jpeg
new file mode 100644
index 0000000..4be332f
Binary files /dev/null and b/ref/spindle_speeds.jpeg differ
diff --git a/src/Automata/Registers.php b/src/Automata/DataRegisters.php
similarity index 55%
rename from src/Automata/Registers.php
rename to src/Automata/DataRegisters.php
index 870521d..a59a876 100644
--- a/src/Automata/Registers.php
+++ b/src/Automata/DataRegisters.php
@@ -2,7 +2,7 @@
 
 namespace Automata;
 
-class Registers
+class DataRegisters
 {
 	public int $B = 0;  // Traverse information
 	public int $X = 0;  // Dimension along X-axis
@@ -17,5 +17,14 @@ class Registers
 	public int $T = 0;  // Tool number
 	public int $H = 0;  // Additional functions (unused)
 	public int $M = 0;  // Auxiliary functions
-	public int $E = 0;  // Number of repetitions / multiple meanins
+	public int $E = 0;  // Number of repetitions / multiple meanings
+	// Modals
+	public int $TM = 0;     // Traverse (0, 1, 2, 3)
+	public int $PS = 18;    // Plane Selection (18, 19, 20)
+	public int $RC = 40;    // Radius Compensation
+	public int $DM = 90;    // Dimension (90, 91)
+	public int $WC = 0;     // Work Cycle (null, 81, 84, 85, 86)
+	public int $CM = 8;     // Coolant (8, 9)
+	public int $SM = 5;     // Spindle (3, 4, 5)
+	public int $TC = 10;    // Table Clamping (10, 11)
 }
diff --git a/src/Automata/InstructionSet.php b/src/Automata/InstructionSet.php
new file mode 100644
index 0000000..a094953
--- /dev/null
+++ b/src/Automata/InstructionSet.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Automata;
+
+use Program\Block;
+
+class InstructionSet
+{
+	private Machine $machine;
+	/** @var callable<Machine>[] */
+	private array $map;
+
+
+	public function __construct(Machine $machine)
+	{
+		$this->machine = $machine;
+		$this->map = [];
+	}
+
+
+	public function apply(Block $block): void
+	{
+		$words = $block->words;
+		while ($word = array_shift($words)) {
+			$method = "{$word}";
+			if (!method_exists($this, $method)) {
+				continue;
+			}
+			$this->{$method}($block);
+			break;
+		}
+	}
+
+
+	public function G22(Block $block): void
+	{
+		$number = $block->valueOf('X');
+		$this->machine->SPMC->loadProgram($number);
+		$this->machine->AMC = $this->machine->SPMC;
+	}
+}
diff --git a/src/Automata/Machine.php b/src/Automata/Machine.php
index 344e216..3cadab1 100644
--- a/src/Automata/Machine.php
+++ b/src/Automata/Machine.php
@@ -2,79 +2,57 @@
 
 namespace Automata;
 
-use Automata\Storage\ProgramMemory;
-use Automata\Storage\ToolMemory;
-use Program\Block;
-use Program\Program;
-use Program\Word;
-use RuntimeException;
-use SplStack;
+use Automata\Memory\MemoryController;
+use Automata\Memory\ProgramMemory;
+use Automata\Memory\ToolMemory;
 
-/*
- * executing a program:
- * - load parts program
- * - execute line by line
- * - load sub program
- * - execute lines from subprogram
- * - back to parts program
- */
 class Machine
 {
-	public State $state;
-	public ToolMemory $toolMemory;
-	public ProgramMemory $subProgramMemory;
-	public ProgramMemory $partProgramMemory;
-	/** @var SplStack|Program[] */
-	private SplStack $programStack;
-	private ?Program $activeProgram = null;
-	private Definitions $definitions;
+	public DataRegisters $DR;
+	public InstructionSet $IS;
+	public ToolMemory $TM;
+	public ProgramMemory $SPM;
+	public ProgramMemory $PPM;
+	public MemoryController $SPMC;
+	public MemoryController $PPMC;
+	public ?MemoryController $AMC;
 
 
 	public function __construct()
 	{
-		$this->state = new State();
-		$this->definitions = new Definitions();
-		$this->toolMemory = new ToolMemory();
-		$this->subProgramMemory = new ProgramMemory();
-		$this->partProgramMemory = new ProgramMemory();
-		$this->programStack = new SplStack();
+		$this->DR = new DataRegisters();
+		$this->IS = new InstructionSet($this);
+		$this->TM = new ToolMemory();
+		$this->SPM = new ProgramMemory();
+		$this->PPM = new ProgramMemory();
+		$this->SPMC = new MemoryController($this->SPM);
+		$this->PPMC = new MemoryController($this->PPM);
+		$this->AMC = $this->PPMC;
 	}
 
 
 	public function loadProgram(int $N): void
 	{
-		$this->programStack = new SplStack();
-		$program = $this->partProgramMemory->read($N);
-		$this->programStack->push($program);
+		$this->PPMC->loadProgram($N);
+		$this->AMC = $this->PPMC;
 	}
 
 
-	public function start(): void
+	public function step(): void
 	{
-		$this->activeProgram = $this->programStack->pop();
-		if (is_null($this->activeProgram)) {
-			throw new RuntimeException('No program loaded');
-		}
-		foreach ($this->activeProgram as $block) {
-			$this->executeBlock($block);
-		}
-	}
-
-	private function executeBlock(Block $block): void
-	{
-		/** @var Word[] $words */
-		$words = $block->words;
-		while ($word = array_shift($words)) {
-			$this->state->apply($word);
-			system('clear');
-			dump($this->state);
-			readline();
+		$block = $this->AMC->next();
+		if (is_null($block) && $this->AMC === $this->SPMC) {
+			// SP ended, back to PP
+			$this->AMC = $this->PPMC;
+			$block = $this->AMC->next();
 		}
+		$this->IS->apply($block);
 	}
 
 
 	public function reset(): void
 	{
-		$this->activeProgram = null;
+		$this->PPMC->reset();
+		$this->SPMC->reset();
 	}
 }
diff --git a/src/Automata/Memory/MemoryController.php b/src/Automata/Memory/MemoryController.php
new file mode 100644
index 0000000..7e44363
--- /dev/null
+++ b/src/Automata/Memory/MemoryController.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Automata\Memory;
+
+use Countable;
+use InvalidArgumentException;
+use Program\Block;
+use RuntimeException;
+
+class MemoryController implements Countable
+{
+	private ProgramMemory $memory;
+	/** @var Block[]|null */
+	private ?array $blocks;
+
+
+	public function __construct(ProgramMemory $memory)
+	{
+		$this->memory = $memory;
+		$this->blocks = null;
+	}
+
+
+	public function loadProgram(int $N): void
+	{
+		$program = $this->memory->read($N);
+		if (!$program) {
+			throw new InvalidArgumentException("Program N{$N} not found");
+		}
+		$this->blocks = $program->getIterator()->getArrayCopy();
+	}
+
+
+	public function reset(): void
+	{
+		$this->blocks = null;
+	}
+
+
+	public function count()
+	{
+		return count($this->blocks);
+	}
+
+
+	public function next(): ?Block
+	{
+		$this->guardNoProgramLoaded();
+
+		return array_shift($this->blocks);
+	}
+
+
+	public function ready(): bool
+	{
+		return !empty($this->blocks);
+	}
+
+
+	private function guardNoProgramLoaded(): void
+	{
+		if (is_null($this->blocks)) {
+			throw new RuntimeException('No program loaded in memory');
+		}
+	}
+}
diff --git a/src/Automata/Storage/ProgramMemory.php b/src/Automata/Memory/ProgramMemory.php
similarity index 86%
rename from src/Automata/Storage/ProgramMemory.php
rename to src/Automata/Memory/ProgramMemory.php
index 0261be1..dbece46 100644
--- a/src/Automata/Storage/ProgramMemory.php
+++ b/src/Automata/Memory/ProgramMemory.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Automata\Storage;
+namespace Automata\Memory;
 
 use InvalidArgumentException;
 use Program\Program;
@@ -11,7 +11,7 @@ class ProgramMemory
 	private array $memory = [];
 
 
-	public function save(Program $program): void
+	public function write(Program $program): void
 	{
 		$this->guardInvalidProgramNumber($program->N);
 		$this->memory[$program->N] = $program;
@@ -30,5 +30,4 @@ class ProgramMemory
 			throw new InvalidArgumentException('Program number must be in range 9001 - 9998');
 		}
 	}
-
 }
diff --git a/src/Automata/Storage/ToolMemory.php b/src/Automata/Memory/ToolMemory.php
similarity index 70%
rename from src/Automata/Storage/ToolMemory.php
rename to src/Automata/Memory/ToolMemory.php
index a94d145..0c5c0e1 100644
--- a/src/Automata/Storage/ToolMemory.php
+++ b/src/Automata/Memory/ToolMemory.php
@@ -1,24 +1,24 @@
 <?php
 
-namespace Automata\Storage;
+namespace Automata\Memory;
 
-use Automata\Tool;
+use Automata\ToolData;
 use InvalidArgumentException;
 
 class ToolMemory
 {
-	/** @var Tool[] */
+	/** @var ToolData[] */
 	private array $memory = [];
 
 
-	public function save(Tool $tool): void
+	public function write(ToolData $tool): void
 	{
 		$this->guardInvalidToolNumber($tool->T);
 		$this->memory[$tool->T] = $tool;
 	}
 
 
-	public function read(int $T): ?Tool
+	public function read(int $T): ?ToolData
 	{
 		return @$this->memory[$T];
 	}
@@ -30,5 +30,4 @@ class ToolMemory
 			throw new InvalidArgumentException('Tool number must be in range 1 - 64');
 		}
 	}
-
 }
diff --git a/src/Automata/State.php b/src/Automata/State.php
deleted file mode 100644
index 215a4b5..0000000
--- a/src/Automata/State.php
+++ /dev/null
@@ -1,71 +0,0 @@
-<?php
-
-namespace Automata;
-
-use Automata\Modes\G\DimensionMode;
-use Automata\Modes\G\PlaneSelection;
-use Automata\Modes\G\RadiusCompensation;
-use Automata\Modes\G\TraverseMode;
-use Automata\Modes\G\WorkCycle;
-use Automata\Modes\M\CoolantMode;
-use Automata\Modes\M\SpindleMode;
-use Automata\Modes\M\TableClampingMode;
-use Program\Word;
-
-class State
-{
-	public Registers $registers;
-	// G
-	public TraverseMode $traverseMode;
-	public PlaneSelection $planeSelection;
-	public RadiusCompensation $radiusCompensation;
-	public DimensionMode $dimensionMode;
-	public WorkCycle $workCycleSelection;
-	// M
-	public CoolantMode $coolantMode;
-	public SpindleMode $spindleMode;
-	public TableClampingMode $tableClamping;
-
-
-	public function __construct()
-	{
-		$this->registers = new Registers();
-		$this->traverseMode = new TraverseMode(0);
-		$this->planeSelection = new PlaneSelection(17);
-		$this->radiusCompensation = new RadiusCompensation(40);
-		$this->dimensionMode = new DimensionMode(90);
-		$this->workCycleSelection = new WorkCycle(0);
-
-		$this->coolantMode = new CoolantMode(9);
-		$this->spindleMode = new SpindleMode(5);
-		$this->tableClamping = new TableClampingMode(10);
-	}
-
-
-	public function apply(Word $word): void
-	{
-		if ($word->register === 'G') {
-			$this->traverseMode->apply($word->value);
-			$this->planeSelection->apply($word->value);
-			$this->radiusCompensation->apply($word->value);
-			$this->dimensionMode->apply($word->value);
-			$this->workCycleSelection->apply($word->value);
-
-			// TODO Handle other G commands
-
-			return;
-		}
-		if ($word->register === 'M') {
-			$this->coolantMode->apply($word->value);
-			$this->spindleMode->apply($word->value);
-			$this->tableClamping->apply($word->value);
-
-			// TODO Handle other M commands
-			return;
-		}
-
-		if (property_exists($this->registers, $word->register)) {
-			$this->registers->{$word->register} = $word->value;
-		}
-	}
-}
diff --git a/src/Automata/Tool.php b/src/Automata/ToolData.php
similarity index 94%
rename from src/Automata/Tool.php
rename to src/Automata/ToolData.php
index 6004806..be6cfe0 100644
--- a/src/Automata/Tool.php
+++ b/src/Automata/ToolData.php
@@ -2,7 +2,7 @@
 
 namespace Automata;
 
-class Tool
+class ToolData
 {
 	public int $T;  // Tool number
 	public int $X;  // Radius in 0.001 mm
diff --git a/src/Program/Block.php b/src/Program/Block.php
index 9861a55..db9c5ac 100644
--- a/src/Program/Block.php
+++ b/src/Program/Block.php
@@ -2,6 +2,8 @@
 
 namespace Program;
 
+use RuntimeException;
+
 class Block
 {
 	public string $N;
@@ -20,4 +22,27 @@ class Block
 	{
 		$this->words[] = $word;
 	}
+
+
+	public function valueOf(string $register): int
+	{
+		foreach ($this->words as $word) {
+			if ($word->register === $register) {
+				return $word->value;
+			}
+		}
+
+		throw new RuntimeException("No word in block for register '$register'");
+	}
+
+
+	public function __toString()
+	{
+		$buffer = "$this->N\t";
+		foreach ($this->words as $word) {
+			$buffer .= "$word\t";
+		}
+
+		return $buffer;
+	}
 }
diff --git a/src/ProgramLoader.php b/src/ProgramLoader.php
index 9749c3c..d615479 100644
--- a/src/ProgramLoader.php
+++ b/src/ProgramLoader.php
@@ -11,12 +11,12 @@ class ProgramLoader
 
 		foreach (glob(__DIR__ . '/../programs/part/*') as $partProgramFile) {
 			$partProgram = $parser->parseFile($partProgramFile);
-			$machine->partProgramMemory->save($partProgram);
+			$machine->PPM->write($partProgram);
 		}
 
 		foreach (glob(__DIR__ . '/../programs/sub/*') as $subProgramFile) {
 			$subProgram = $parser->parseFile($subProgramFile);
-			$machine->subProgramMemory->save($subProgram);
+			$machine->SPM->write($subProgram);
 		}
 	}
 }