diff --git a/src/asm/Address.go b/src/asm/Address.go
new file mode 100644
index 0000000..14b073b
--- /dev/null
+++ b/src/asm/Address.go
@@ -0,0 +1,4 @@
+package asm
+
+// Address represents a memory address.
+type Address = uint32
diff --git a/src/asm/Assembler.go b/src/asm/Assembler.go
index 8f0e6d3..a751e33 100644
--- a/src/asm/Assembler.go
+++ b/src/asm/Assembler.go
@@ -6,37 +6,46 @@ import (
 
 // Assembler contains a list of instructions.
 type Assembler struct {
-	Instructions []Instruction
+	instructions []Instruction
+	labels       map[string]int
 }
 
 // New creates a new assembler.
 func New() *Assembler {
 	return &Assembler{
-		Instructions: make([]Instruction, 0, 8),
+		instructions: make([]Instruction, 0, 8),
+		labels:       map[string]int{},
 	}
 }
 
 // Finalize generates the final machine code.
-func (list *Assembler) Finalize() *Result {
+func (a *Assembler) Finalize() *Result {
 	final := Result{}
 
-	for _, instr := range list.Instructions {
+	for _, instr := range a.instructions {
 		instr.Write(&final.Code)
 	}
 
 	return &final
 }
 
-func (list *Assembler) MoveRegisterNumber(reg register.ID, number uint64) {
-	list.Instructions = append(list.Instructions, Instruction{
+// AddLabel creates a new label at the current position.
+func (a *Assembler) AddLabel(name string) {
+	a.labels[name] = len(a.instructions)
+}
+
+// MoveRegisterNumber moves a number into the given register.
+func (a *Assembler) MoveRegisterNumber(reg register.ID, number uint64) {
+	a.instructions = append(a.instructions, Instruction{
 		Mnemonic:    MOV,
 		Destination: reg,
 		Number:      number,
 	})
 }
 
-func (list *Assembler) Syscall() {
-	list.Instructions = append(list.Instructions, Instruction{
+// Syscall executes a kernel function.
+func (a *Assembler) Syscall() {
+	a.instructions = append(a.instructions, Instruction{
 		Mnemonic: SYSCALL,
 	})
 }
diff --git a/src/asm/Instruction.go b/src/asm/Instruction.go
index 210f253..1883cee 100644
--- a/src/asm/Instruction.go
+++ b/src/asm/Instruction.go
@@ -26,6 +26,7 @@ func (x *Instruction) Write(w io.ByteWriter) {
 	}
 }
 
+// String returns the assembler representation of the instruction.
 func (x *Instruction) String() string {
 	switch x.Mnemonic {
 	case MOV: