diff --git a/examples/hello/hello.q b/examples/hello/hello.q
index 4f723f0..76d8d21 100644
--- a/examples/hello/hello.q
+++ b/examples/hello/hello.q
@@ -1,3 +1,3 @@
 main() {
-	print("Hello")
+	syscall(60, 0)
 }
diff --git a/src/arch/arm64/Syscall.go b/src/arch/arm64/Syscall.go
deleted file mode 100644
index 37e0b9e..0000000
--- a/src/arch/arm64/Syscall.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package register
-
-import "git.akyoto.dev/cli/q/src/register"
-
-const (
-	SyscallNumber = register.R8
-	SyscallReturn = register.R0
-)
-
-var SyscallArgs = []register.ID{
-	register.R0,
-	register.R1,
-	register.R2,
-	register.R3,
-	register.R4,
-	register.R5,
-}
diff --git a/src/arch/x64/Syscall.go b/src/arch/x64/Syscall.go
deleted file mode 100644
index 132e560..0000000
--- a/src/arch/x64/Syscall.go
+++ /dev/null
@@ -1,22 +0,0 @@
-package x64
-
-import "git.akyoto.dev/cli/q/src/register"
-
-const (
-	SyscallNumber = register.R0 // rax
-	SyscallReturn = register.R0 // rax
-)
-
-var SyscallArgs = []register.ID{
-	register.R7, // rdi
-	register.R6, // rsi
-	register.R2, // rdx
-	register.R10,
-	register.R8,
-	register.R9,
-}
-
-// Syscall is the primary way to communicate with the OS kernel.
-func Syscall(code []byte) []byte {
-	return append(code, 0x0f, 0x05)
-}
diff --git a/src/asm/Address.go b/src/asm/Address.go
deleted file mode 100644
index 14b073b..0000000
--- a/src/asm/Address.go
+++ /dev/null
@@ -1,4 +0,0 @@
-package asm
-
-// Address represents a memory address.
-type Address = uint32
diff --git a/src/asm/Assembler.go b/src/asm/Assembler.go
deleted file mode 100644
index 5de2ff9..0000000
--- a/src/asm/Assembler.go
+++ /dev/null
@@ -1,93 +0,0 @@
-package asm
-
-import (
-	"encoding/binary"
-
-	"git.akyoto.dev/cli/q/src/arch/x64"
-	"git.akyoto.dev/cli/q/src/config"
-	"git.akyoto.dev/cli/q/src/log"
-	"git.akyoto.dev/cli/q/src/register"
-)
-
-// Assembler contains a list of instructions.
-type Assembler struct {
-	Instructions []Instruction
-}
-
-// New creates a new assembler.
-func New() *Assembler {
-	return &Assembler{
-		Instructions: make([]Instruction, 0, 8),
-	}
-}
-
-// Finalize generates the final machine code.
-func (a *Assembler) Finalize() ([]byte, []byte) {
-	code := make([]byte, 0, len(a.Instructions)*8)
-	data := make(Data, 0, 16)
-	pointers := []Pointer{}
-
-	for _, x := range a.Instructions {
-		switch x.Mnemonic {
-		case MOV:
-			code = x64.MoveRegNum32(code, uint8(x.Destination), uint32(x.Number))
-
-		case MOVDATA:
-			code = x64.MoveRegNum32(code, uint8(x.Destination), 0)
-
-			pointers = append(pointers, Pointer{
-				Position: Address(len(code) - 4),
-				Address:  data.Add(x.Data),
-			})
-
-		case SYSCALL:
-			code = x64.Syscall(code)
-		}
-	}
-
-	if config.Verbose {
-		for _, x := range a.Instructions {
-			log.Info.Println(x.String())
-		}
-	}
-
-	dataStart := config.BaseAddress + config.CodeOffset + Address(len(code))
-
-	for _, pointer := range pointers {
-		slice := code[pointer.Position : pointer.Position+4]
-		address := dataStart + pointer.Address
-		binary.LittleEndian.PutUint32(slice, address)
-	}
-
-	return code, data
-}
-
-// Merge combines the contents of this assembler with another one.
-func (a *Assembler) Merge(b *Assembler) {
-	a.Instructions = append(a.Instructions, b.Instructions...)
-}
-
-// MoveRegisterData moves a data section address into the given register.
-func (a *Assembler) MoveRegisterData(reg register.ID, data []byte) {
-	a.Instructions = append(a.Instructions, Instruction{
-		Mnemonic:    MOVDATA,
-		Destination: reg,
-		Data:        data,
-	})
-}
-
-// 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,
-	})
-}
-
-// Syscall executes a kernel function.
-func (a *Assembler) Syscall() {
-	a.Instructions = append(a.Instructions, Instruction{
-		Mnemonic: SYSCALL,
-	})
-}
diff --git a/src/asm/Assembler_test.go b/src/asm/Assembler_test.go
deleted file mode 100644
index ed47f32..0000000
--- a/src/asm/Assembler_test.go
+++ /dev/null
@@ -1,41 +0,0 @@
-package asm_test
-
-import (
-	"testing"
-
-	"git.akyoto.dev/cli/q/src/arch/x64"
-	"git.akyoto.dev/cli/q/src/asm"
-	"git.akyoto.dev/cli/q/src/os/linux"
-	"git.akyoto.dev/go/assert"
-)
-
-func TestHello(t *testing.T) {
-	a := asm.New()
-
-	hello := []byte("Hello\n")
-	a.MoveRegisterNumber(x64.SyscallNumber, linux.Write)
-	a.MoveRegisterNumber(x64.SyscallArgs[0], 1)
-	a.MoveRegisterData(x64.SyscallArgs[1], hello)
-	a.MoveRegisterNumber(x64.SyscallArgs[2], uint64(len(hello)))
-	a.Syscall()
-
-	a.MoveRegisterNumber(x64.SyscallNumber, linux.Exit)
-	a.MoveRegisterNumber(x64.SyscallArgs[0], 0)
-	a.Syscall()
-
-	code, data := a.Finalize()
-
-	assert.DeepEqual(t, code, []byte{
-		0xb8, 0x01, 0x00, 0x00, 0x00,
-		0xbf, 0x01, 0x00, 0x00, 0x00,
-		0xbe, 0xa2, 0x00, 0x40, 0x00,
-		0xba, 0x06, 0x00, 0x00, 0x00,
-		0x0f, 0x05,
-
-		0xb8, 0x3c, 0x00, 0x00, 0x00,
-		0xbf, 0x00, 0x00, 0x00, 0x00,
-		0x0f, 0x05,
-	})
-
-	assert.DeepEqual(t, data, hello)
-}
diff --git a/src/asm/Data.go b/src/asm/Data.go
deleted file mode 100644
index 418a898..0000000
--- a/src/asm/Data.go
+++ /dev/null
@@ -1,20 +0,0 @@
-package asm
-
-import "bytes"
-
-// Data represents the static read-only data.
-type Data []byte
-
-// Add adds the given bytes to the data block if this sequence of bytes doesn't exist yet.
-// It returns the address relative to the start of the data section.
-func (data *Data) Add(block []byte) Address {
-	position := bytes.Index(*data, block)
-
-	if position != -1 {
-		return Address(position)
-	}
-
-	address := Address(len(*data))
-	*data = append(*data, block...)
-	return address
-}
diff --git a/src/asm/Instruction.go b/src/asm/Instruction.go
deleted file mode 100644
index 0c91ee1..0000000
--- a/src/asm/Instruction.go
+++ /dev/null
@@ -1,30 +0,0 @@
-package asm
-
-import (
-	"fmt"
-
-	"git.akyoto.dev/cli/q/src/register"
-)
-
-// Instruction represents a single instruction which can be converted to machine code.
-type Instruction struct {
-	Mnemonic    Mnemonic
-	Source      register.ID
-	Destination register.ID
-	Number      uint64
-	Data        []byte
-}
-
-// String returns the assembler representation of the instruction.
-func (x *Instruction) String() string {
-	switch x.Mnemonic {
-	case MOV:
-		return fmt.Sprintf("%s %s, %x", x.Mnemonic, x.Destination, x.Number)
-	case MOVDATA:
-		return fmt.Sprintf("%s %s, %v", x.Mnemonic, x.Destination, x.Data)
-	case SYSCALL:
-		return x.Mnemonic.String()
-	default:
-		return ""
-	}
-}
diff --git a/src/build/Build.go b/src/build/Build.go
index f73045a..c7029cb 100644
--- a/src/build/Build.go
+++ b/src/build/Build.go
@@ -1,12 +1,7 @@
 package build
 
 import (
-	"bufio"
-	"os"
 	"path/filepath"
-
-	"git.akyoto.dev/cli/q/src/compiler"
-	"git.akyoto.dev/cli/q/src/elf"
 )
 
 // Build describes a compiler build.
@@ -25,7 +20,7 @@ func New(directory string) *Build {
 
 // Run parses the input files and generates an executable file.
 func (build *Build) Run() error {
-	functions, err := compiler.Compile(build.Directory)
+	functions, err := Compile(build.Directory)
 
 	if err != nil {
 		return err
@@ -35,33 +30,12 @@ func (build *Build) Run() error {
 		return nil
 	}
 
-	code, data := compiler.Finalize(functions)
-	return writeToDisk(build.Executable(), code, data)
+	path := build.Executable()
+	code, data := Finalize(functions)
+	return Write(path, code, data)
 }
 
 // Executable returns the path to the executable.
 func (build *Build) Executable() string {
 	return filepath.Join(build.Directory, filepath.Base(build.Directory))
 }
-
-// writeToDisk writes the executable file to disk.
-func writeToDisk(filePath string, code []byte, data []byte) error {
-	file, err := os.Create(filePath)
-
-	if err != nil {
-		return err
-	}
-
-	buffer := bufio.NewWriter(file)
-	executable := elf.New(code, data)
-	executable.Write(buffer)
-	buffer.Flush()
-
-	err = file.Close()
-
-	if err != nil {
-		return err
-	}
-
-	return os.Chmod(filePath, 0755)
-}
diff --git a/src/build/Build_test.go b/src/build/Build_test.go
new file mode 100644
index 0000000..7c91f0b
--- /dev/null
+++ b/src/build/Build_test.go
@@ -0,0 +1,24 @@
+package build_test
+
+import (
+	"testing"
+
+	"git.akyoto.dev/cli/q/src/build"
+	"git.akyoto.dev/go/assert"
+)
+
+func TestBuild(t *testing.T) {
+	b := build.New("../../examples/hello")
+	assert.Nil(t, b.Run())
+}
+
+func TestSkipExecutable(t *testing.T) {
+	b := build.New("../../examples/hello")
+	b.WriteExecutable = false
+	assert.Nil(t, b.Run())
+}
+
+func TestNonExisting(t *testing.T) {
+	b := build.New("does-not-exist")
+	assert.NotNil(t, b.Run())
+}
diff --git a/src/compiler/Compile.go b/src/build/Compile.go
similarity index 94%
rename from src/compiler/Compile.go
rename to src/build/Compile.go
index 5311d01..1d1ffc1 100644
--- a/src/compiler/Compile.go
+++ b/src/build/Compile.go
@@ -1,6 +1,8 @@
-package compiler
+package build
 
-import "sync"
+import (
+	"sync"
+)
 
 // Compile compiles all the functions.
 func Compile(directory string) (map[string]*Function, error) {
diff --git a/src/compiler/Finalize.go b/src/build/Finalize.go
similarity index 51%
rename from src/compiler/Finalize.go
rename to src/build/Finalize.go
index 56095f4..413ce71 100644
--- a/src/compiler/Finalize.go
+++ b/src/build/Finalize.go
@@ -1,9 +1,7 @@
-package compiler
+package build
 
 import (
-	"git.akyoto.dev/cli/q/src/arch/x64"
-	"git.akyoto.dev/cli/q/src/asm"
-	"git.akyoto.dev/cli/q/src/os/linux"
+	"git.akyoto.dev/cli/q/src/build/asm"
 )
 
 // Finalize generates the final machine code.
@@ -14,10 +12,6 @@ func Finalize(functions map[string]*Function) ([]byte, []byte) {
 		a.Merge(&f.Assembler)
 	}
 
-	a.MoveRegisterNumber(x64.SyscallNumber, linux.Exit)
-	a.MoveRegisterNumber(x64.SyscallArgs[0], 0)
-	a.Syscall()
-
 	code, data := a.Finalize()
 	return code, data
 }
diff --git a/src/build/Function.go b/src/build/Function.go
new file mode 100644
index 0000000..11c84ed
--- /dev/null
+++ b/src/build/Function.go
@@ -0,0 +1,96 @@
+package build
+
+import (
+	"fmt"
+	"strconv"
+
+	"git.akyoto.dev/cli/q/src/build/arch/x64"
+	"git.akyoto.dev/cli/q/src/build/asm"
+	"git.akyoto.dev/cli/q/src/build/config"
+	"git.akyoto.dev/cli/q/src/build/token"
+	"git.akyoto.dev/go/color/ansi"
+)
+
+// Function represents a function.
+type Function struct {
+	Name      string
+	Head      token.List
+	Body      token.List
+	Assembler asm.Assembler
+}
+
+// Compile turns a function into machine code.
+func (f *Function) Compile() {
+	if config.Verbose {
+		ansi.Underline.Println(f.Name)
+	}
+
+	for _, line := range f.Lines() {
+		if config.Verbose {
+			fmt.Println("[line]", line)
+		}
+
+		if len(line) == 0 {
+			continue
+		}
+
+		if line[0].Kind == token.Identifier && line[0].Text() == "syscall" {
+			paramTokens := line[2 : len(line)-1]
+			start := 0
+			i := 0
+			var parameters []token.List
+
+			for i < len(paramTokens) {
+				if paramTokens[i].Kind == token.Separator {
+					parameters = append(parameters, paramTokens[start:i])
+					start = i + 1
+				}
+
+				i++
+			}
+
+			if i != start {
+				parameters = append(parameters, paramTokens[start:i])
+			}
+
+			for i, list := range parameters {
+				if list[0].Kind == token.Number {
+					numAsText := list[0].Text()
+					n, _ := strconv.Atoi(numAsText)
+					f.Assembler.MoveRegisterNumber(x64.SyscallArgs[i], uint64(n))
+				}
+			}
+
+			f.Assembler.Syscall()
+		}
+	}
+}
+
+// Lines returns the lines in the function body.
+func (f *Function) Lines() []token.List {
+	var (
+		lines []token.List
+		start = 0
+		i     = 0
+	)
+
+	for i < len(f.Body) {
+		if f.Body[i].Kind == token.NewLine {
+			lines = append(lines, f.Body[start:i])
+			start = i + 1
+		}
+
+		i++
+	}
+
+	if i != start {
+		lines = append(lines, f.Body[start:i])
+	}
+
+	return lines
+}
+
+// String returns the function name.
+func (f *Function) String() string {
+	return f.Name
+}
diff --git a/src/compiler/Scan.go b/src/build/Scan.go
similarity index 94%
rename from src/compiler/Scan.go
rename to src/build/Scan.go
index d0ef625..ae24220 100644
--- a/src/compiler/Scan.go
+++ b/src/build/Scan.go
@@ -1,4 +1,4 @@
-package compiler
+package build
 
 import (
 	"os"
@@ -6,8 +6,8 @@ import (
 	"strings"
 	"sync"
 
-	"git.akyoto.dev/cli/q/src/directory"
-	"git.akyoto.dev/cli/q/src/token"
+	"git.akyoto.dev/cli/q/src/build/directory"
+	"git.akyoto.dev/cli/q/src/build/token"
 )
 
 // Scan scans the directory.
diff --git a/src/build/Write.go b/src/build/Write.go
new file mode 100644
index 0000000..f6385bb
--- /dev/null
+++ b/src/build/Write.go
@@ -0,0 +1,29 @@
+package build
+
+import (
+	"bufio"
+	"os"
+
+	"git.akyoto.dev/cli/q/src/build/elf"
+)
+
+// Write writes the executable file to disk.
+func Write(filePath string, code []byte, data []byte) error {
+	file, err := os.Create(filePath)
+
+	if err != nil {
+		return err
+	}
+
+	buffer := bufio.NewWriter(file)
+	executable := elf.New(code, data)
+	executable.Write(buffer)
+	buffer.Flush()
+	err = file.Close()
+
+	if err != nil {
+		return err
+	}
+
+	return os.Chmod(filePath, 0755)
+}
diff --git a/src/build/arch/arm64/Syscall.go b/src/build/arch/arm64/Syscall.go
new file mode 100644
index 0000000..fb6495b
--- /dev/null
+++ b/src/build/arch/arm64/Syscall.go
@@ -0,0 +1,9 @@
+package register
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+const (
+	SyscallReturn = 0
+)
+
+var SyscallArgs = []cpu.Register{8, 0, 1, 2, 3, 4, 5}
diff --git a/src/arch/x64/Call.go b/src/build/arch/x64/Call.go
similarity index 100%
rename from src/arch/x64/Call.go
rename to src/build/arch/x64/Call.go
diff --git a/src/arch/x64/Move.go b/src/build/arch/x64/Move.go
similarity index 100%
rename from src/arch/x64/Move.go
rename to src/build/arch/x64/Move.go
diff --git a/src/arch/x64/Return.go b/src/build/arch/x64/Return.go
similarity index 100%
rename from src/arch/x64/Return.go
rename to src/build/arch/x64/Return.go
diff --git a/src/build/arch/x64/Syscall.go b/src/build/arch/x64/Syscall.go
new file mode 100644
index 0000000..6251de9
--- /dev/null
+++ b/src/build/arch/x64/Syscall.go
@@ -0,0 +1,14 @@
+package x64
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+const (
+	SyscallReturn = 0 // rax
+)
+
+var SyscallArgs = []cpu.Register{0, 7, 6, 2, 10, 8, 9}
+
+// Syscall is the primary way to communicate with the OS kernel.
+func Syscall(code []byte) []byte {
+	return append(code, 0x0f, 0x05)
+}
diff --git a/src/arch/x64/x64_test.go b/src/build/arch/x64/x64_test.go
similarity index 91%
rename from src/arch/x64/x64_test.go
rename to src/build/arch/x64/x64_test.go
index 8fb7c21..b39570d 100644
--- a/src/arch/x64/x64_test.go
+++ b/src/build/arch/x64/x64_test.go
@@ -3,7 +3,7 @@ package x64_test
 import (
 	"testing"
 
-	"git.akyoto.dev/cli/q/src/arch/x64"
+	"git.akyoto.dev/cli/q/src/build/arch/x64"
 	"git.akyoto.dev/go/assert"
 )
 
diff --git a/src/build/asm/Assembler.go b/src/build/asm/Assembler.go
new file mode 100644
index 0000000..94a4ce7
--- /dev/null
+++ b/src/build/asm/Assembler.go
@@ -0,0 +1,66 @@
+package asm
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"git.akyoto.dev/cli/q/src/build/arch/x64"
+	"git.akyoto.dev/cli/q/src/build/config"
+)
+
+// Assembler contains a list of instructions.
+type Assembler struct {
+	Instructions []Instruction
+}
+
+// New creates a new assembler.
+func New() *Assembler {
+	return &Assembler{
+		Instructions: make([]Instruction, 0, 8),
+	}
+}
+
+// Finalize generates the final machine code.
+func (a *Assembler) Finalize() ([]byte, []byte) {
+	code := make([]byte, 0, len(a.Instructions)*8)
+	data := make([]byte, 0, 16)
+	pointers := []Pointer{}
+
+	for _, x := range a.Instructions {
+		switch x.Mnemonic {
+		case MOVE:
+			code = x64.MoveRegNum32(code, uint8(x.Data.(RegisterNumber).Register), uint32(x.Data.(RegisterNumber).Number))
+
+			if x.Data.(RegisterNumber).IsPointer {
+				pointers = append(pointers, Pointer{
+					Position: Address(len(code) - 4),
+					Address:  Address(x.Data.(RegisterNumber).Number),
+				})
+			}
+
+		case SYSCALL:
+			code = x64.Syscall(code)
+		}
+	}
+
+	if config.Verbose {
+		for _, x := range a.Instructions {
+			fmt.Println("[asm]", x.String())
+		}
+	}
+
+	dataStart := config.BaseAddress + config.CodeOffset + Address(len(code))
+
+	for _, pointer := range pointers {
+		slice := code[pointer.Position : pointer.Position+4]
+		address := dataStart + pointer.Address
+		binary.LittleEndian.PutUint32(slice, address)
+	}
+
+	return code, data
+}
+
+// Merge combines the contents of this assembler with another one.
+func (a *Assembler) Merge(b *Assembler) {
+	a.Instructions = append(a.Instructions, b.Instructions...)
+}
diff --git a/src/build/asm/Instruction.go b/src/build/asm/Instruction.go
new file mode 100644
index 0000000..966ce75
--- /dev/null
+++ b/src/build/asm/Instruction.go
@@ -0,0 +1,19 @@
+package asm
+
+import "fmt"
+
+// Instruction represents a single instruction which can be converted to machine code.
+type Instruction struct {
+	Mnemonic Mnemonic
+	Data     interface{}
+}
+
+// String returns a human readable version.
+func (x *Instruction) String() string {
+	switch data := x.Data.(type) {
+	case RegisterNumber:
+		return fmt.Sprintf("%s %s, %x", x.Mnemonic, data.Register, data.Number)
+	default:
+		return x.Mnemonic.String()
+	}
+}
diff --git a/src/build/asm/Instructions.go b/src/build/asm/Instructions.go
new file mode 100644
index 0000000..0cd9014
--- /dev/null
+++ b/src/build/asm/Instructions.go
@@ -0,0 +1,32 @@
+package asm
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// MoveRegisterNumber moves a number into the given register.
+func (a *Assembler) MoveRegisterNumber(reg cpu.Register, number uint64) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: MOVE,
+		Data: RegisterNumber{
+			Register:  reg,
+			Number:    number,
+			IsPointer: false,
+		},
+	})
+}
+
+// MoveRegisterAddress moves an address into the given register.
+func (a *Assembler) MoveRegisterAddress(reg cpu.Register, address Address) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: MOVE,
+		Data: RegisterNumber{
+			Register:  reg,
+			Number:    uint64(address),
+			IsPointer: true,
+		},
+	})
+}
+
+// Syscall executes a kernel function.
+func (a *Assembler) Syscall() {
+	a.Instructions = append(a.Instructions, Instruction{Mnemonic: SYSCALL})
+}
diff --git a/src/asm/Mnemonic.go b/src/build/asm/Mnemonic.go
similarity index 69%
rename from src/asm/Mnemonic.go
rename to src/build/asm/Mnemonic.go
index 3d3a16c..cd7f033 100644
--- a/src/asm/Mnemonic.go
+++ b/src/build/asm/Mnemonic.go
@@ -4,18 +4,15 @@ type Mnemonic uint8
 
 const (
 	NONE Mnemonic = iota
-	MOV
-	MOVDATA
+	MOVE
 	SYSCALL
 )
 
+// String returns a human readable version.
 func (m Mnemonic) String() string {
 	switch m {
-	case MOV:
-		return "mov"
-
-	case MOVDATA:
-		return "mov"
+	case MOVE:
+		return "move"
 
 	case SYSCALL:
 		return "syscall"
diff --git a/src/asm/Pointer.go b/src/build/asm/Pointer.go
similarity index 81%
rename from src/asm/Pointer.go
rename to src/build/asm/Pointer.go
index 5d13b4f..7063ec5 100644
--- a/src/asm/Pointer.go
+++ b/src/build/asm/Pointer.go
@@ -1,5 +1,8 @@
 package asm
 
+// Address represents a memory address.
+type Address = uint32
+
 // Pointer stores a relative memory address that we can later turn into an absolute one.
 // Position: The machine code offset where the address was inserted.
 // Address:  The offset inside the section.
diff --git a/src/build/asm/RegisterNumber.go b/src/build/asm/RegisterNumber.go
new file mode 100644
index 0000000..445acd1
--- /dev/null
+++ b/src/build/asm/RegisterNumber.go
@@ -0,0 +1,10 @@
+package asm
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// RegisterNumber operates with a register and a number.
+type RegisterNumber struct {
+	Register  cpu.Register
+	Number    uint64
+	IsPointer bool
+}
diff --git a/src/config/config.go b/src/build/config/config.go
similarity index 100%
rename from src/config/config.go
rename to src/build/config/config.go
diff --git a/src/build/cpu/Register.go b/src/build/cpu/Register.go
new file mode 100644
index 0000000..006fc68
--- /dev/null
+++ b/src/build/cpu/Register.go
@@ -0,0 +1,11 @@
+package cpu
+
+import "fmt"
+
+// Register represents the number of the register.
+type Register uint8
+
+// String returns the human readable name of the register.
+func (r Register) String() string {
+	return fmt.Sprintf("r%d", r)
+}
diff --git a/src/directory/Walk.go b/src/build/directory/Walk.go
similarity index 100%
rename from src/directory/Walk.go
rename to src/build/directory/Walk.go
diff --git a/src/directory/Walk_test.go b/src/build/directory/Walk_test.go
similarity index 90%
rename from src/directory/Walk_test.go
rename to src/build/directory/Walk_test.go
index f3f64cf..00c663f 100644
--- a/src/directory/Walk_test.go
+++ b/src/build/directory/Walk_test.go
@@ -3,7 +3,7 @@ package directory_test
 import (
 	"testing"
 
-	"git.akyoto.dev/cli/q/src/directory"
+	"git.akyoto.dev/cli/q/src/build/directory"
 	"git.akyoto.dev/go/assert"
 )
 
diff --git a/src/elf/ELF.go b/src/build/elf/ELF.go
similarity index 97%
rename from src/elf/ELF.go
rename to src/build/elf/ELF.go
index 92d45c6..f284dbc 100644
--- a/src/elf/ELF.go
+++ b/src/build/elf/ELF.go
@@ -4,7 +4,7 @@ import (
 	"encoding/binary"
 	"io"
 
-	"git.akyoto.dev/cli/q/src/config"
+	"git.akyoto.dev/cli/q/src/build/config"
 )
 
 // ELF represents an ELF file.
diff --git a/src/elf/ELF_test.go b/src/build/elf/ELF_test.go
similarity index 77%
rename from src/elf/ELF_test.go
rename to src/build/elf/ELF_test.go
index 45a9aa2..b609d60 100644
--- a/src/elf/ELF_test.go
+++ b/src/build/elf/ELF_test.go
@@ -4,7 +4,7 @@ import (
 	"io"
 	"testing"
 
-	"git.akyoto.dev/cli/q/src/elf"
+	"git.akyoto.dev/cli/q/src/build/elf"
 )
 
 func TestELF(t *testing.T) {
diff --git a/src/elf/Header.go b/src/build/elf/Header.go
similarity index 100%
rename from src/elf/Header.go
rename to src/build/elf/Header.go
diff --git a/src/elf/ProgramHeader.go b/src/build/elf/ProgramHeader.go
similarity index 100%
rename from src/elf/ProgramHeader.go
rename to src/build/elf/ProgramHeader.go
diff --git a/src/elf/SectionHeader.go b/src/build/elf/SectionHeader.go
similarity index 100%
rename from src/elf/SectionHeader.go
rename to src/build/elf/SectionHeader.go
diff --git a/src/elf/elf.md b/src/build/elf/elf.md
similarity index 100%
rename from src/elf/elf.md
rename to src/build/elf/elf.md
diff --git a/src/os/linux/Syscall.go b/src/build/os/linux/Syscall.go
similarity index 100%
rename from src/os/linux/Syscall.go
rename to src/build/os/linux/Syscall.go
diff --git a/src/build/output/Compiler.go b/src/build/output/Compiler.go
new file mode 100644
index 0000000..dbbff06
--- /dev/null
+++ b/src/build/output/Compiler.go
@@ -0,0 +1,27 @@
+package output
+
+import (
+	"fmt"
+
+	"git.akyoto.dev/cli/q/src/build"
+	"git.akyoto.dev/cli/q/src/build/token"
+)
+
+// Compiler implements the arch.Output interface.
+type Compiler struct{}
+
+// Compile turns a function into machine code.
+func (c Compiler) Compile(f *build.Function) {
+	for i, t := range f.Body {
+		if t.Kind == token.Identifier && t.Text() == "print" {
+			// message := f.Body[i+2].Bytes
+			// f.Assembler.MoveRegisterNumber(x64.SyscallNumber, linux.Write)
+			// f.Assembler.MoveRegisterNumber(x64.SyscallArgs[0], 1)
+			// f.Assembler.MoveRegisterData(x64.SyscallArgs[1], message)
+			// f.Assembler.MoveRegisterNumber(x64.SyscallArgs[2], uint64(len(message)))
+			// f.Assembler.Syscall()
+			message := f.Body[i+2].Bytes
+			fmt.Println(message)
+		}
+	}
+}
diff --git a/src/token/Keywords.go b/src/build/token/Keywords.go
similarity index 100%
rename from src/token/Keywords.go
rename to src/build/token/Keywords.go
diff --git a/src/token/Kind.go b/src/build/token/Kind.go
similarity index 100%
rename from src/token/Kind.go
rename to src/build/token/Kind.go
diff --git a/src/token/List.go b/src/build/token/List.go
similarity index 100%
rename from src/token/List.go
rename to src/build/token/List.go
diff --git a/src/token/Token.go b/src/build/token/Token.go
similarity index 100%
rename from src/token/Token.go
rename to src/build/token/Token.go
diff --git a/src/token/Token_test.go b/src/build/token/Token_test.go
similarity index 92%
rename from src/token/Token_test.go
rename to src/build/token/Token_test.go
index 8bcac13..1bc125e 100644
--- a/src/token/Token_test.go
+++ b/src/build/token/Token_test.go
@@ -3,7 +3,7 @@ package token_test
 import (
 	"testing"
 
-	"git.akyoto.dev/cli/q/src/token"
+	"git.akyoto.dev/cli/q/src/build/token"
 	"git.akyoto.dev/go/assert"
 )
 
@@ -96,6 +96,22 @@ func TestNewline(t *testing.T) {
 	})
 }
 
+func TestNumber(t *testing.T) {
+	tokens := token.Tokenize([]byte(`123 -456`))
+	assert.DeepEqual(t, tokens, token.List{
+		{
+			Kind:     token.Number,
+			Bytes:    []byte("123"),
+			Position: 0,
+		},
+		{
+			Kind:     token.Number,
+			Bytes:    []byte("-456"),
+			Position: 4,
+		},
+	})
+}
+
 func TestSeparator(t *testing.T) {
 	tokens := token.Tokenize([]byte("a,b,c"))
 	assert.DeepEqual(t, tokens, token.List{
diff --git a/src/token/Tokenize.go b/src/build/token/Tokenize.go
similarity index 78%
rename from src/token/Tokenize.go
rename to src/build/token/Tokenize.go
index 4692791..d0402e3 100644
--- a/src/token/Tokenize.go
+++ b/src/build/token/Tokenize.go
@@ -96,7 +96,25 @@ func Tokenize(buffer []byte) List {
 				}
 
 				tokens = append(tokens, token)
-				i--
+				continue
+			}
+
+			// Numbers
+			if isNumberStart(buffer[i]) {
+				position := i
+				i++
+
+				for i < len(buffer) && isNumber(buffer[i]) {
+					i++
+				}
+
+				tokens = append(tokens, Token{
+					Number,
+					position,
+					buffer[position:i],
+				})
+
+				continue
 			}
 		}
 
@@ -106,10 +124,22 @@ func Tokenize(buffer []byte) List {
 	return tokens
 }
 
-func isIdentifierStart(c byte) bool {
-	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_'
+func isIdentifier(c byte) bool {
+	return isLetter(c) || isNumber(c) || c == '_'
 }
 
-func isIdentifier(c byte) bool {
-	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || (c >= '0' && c <= '9')
+func isIdentifierStart(c byte) bool {
+	return isLetter(c) || c == '_'
+}
+
+func isLetter(c byte) bool {
+	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
+}
+
+func isNumber(c byte) bool {
+	return (c >= '0' && c <= '9')
+}
+
+func isNumberStart(c byte) bool {
+	return isNumber(c) || c == '-'
 }
diff --git a/src/cli/Build.go b/src/cli/Build.go
index 2974257..2eb6cf2 100644
--- a/src/cli/Build.go
+++ b/src/cli/Build.go
@@ -1,11 +1,11 @@
 package cli
 
 import (
+	"fmt"
 	"strings"
 
 	"git.akyoto.dev/cli/q/src/build"
-	"git.akyoto.dev/cli/q/src/config"
-	"git.akyoto.dev/cli/q/src/log"
+	"git.akyoto.dev/cli/q/src/build/config"
 )
 
 // Build builds an executable.
@@ -22,7 +22,7 @@ func Build(args []string) int {
 
 		default:
 			if strings.HasPrefix(args[i], "-") {
-				log.Error.Printf("Unknown parameter: %s\n", args[i])
+				fmt.Printf("Unknown parameter: %s\n", args[i])
 				return 2
 			}
 
@@ -33,7 +33,7 @@ func Build(args []string) int {
 	err := b.Run()
 
 	if err != nil {
-		log.Error.Println(err)
+		fmt.Println(err)
 		return 1
 	}
 
diff --git a/src/cli/Help.go b/src/cli/Help.go
index 35fa8cd..6ca3b3c 100644
--- a/src/cli/Help.go
+++ b/src/cli/Help.go
@@ -1,14 +1,12 @@
 package cli
 
-import (
-	"git.akyoto.dev/cli/q/src/log"
-)
+import "fmt"
 
 // Help shows the command line argument usage.
 func Help(args []string) int {
-	log.Error.Println("Usage: q [command] [options]")
-	log.Error.Println("")
-	log.Error.Println("    build [directory]")
-	log.Error.Println("    system")
+	fmt.Println("Usage: q [command] [options]")
+	fmt.Println("")
+	fmt.Println("    build [directory]")
+	fmt.Println("    system")
 	return 2
 }
diff --git a/src/cli/Main_test.go b/src/cli/Main_test.go
index 95fcf55..f5ae0a4 100644
--- a/src/cli/Main_test.go
+++ b/src/cli/Main_test.go
@@ -2,21 +2,13 @@ package cli_test
 
 import (
 	"fmt"
-	"io"
 	"os"
 	"testing"
 
 	"git.akyoto.dev/cli/q/src/cli"
-	"git.akyoto.dev/cli/q/src/log"
 	"git.akyoto.dev/go/assert"
 )
 
-func TestMain(m *testing.M) {
-	log.Info.SetOutput(io.Discard)
-	log.Error.SetOutput(io.Discard)
-	os.Exit(m.Run())
-}
-
 func TestCLI(t *testing.T) {
 	type cliTest struct {
 		arguments        []string
diff --git a/src/cli/System.go b/src/cli/System.go
index d76f565..831576c 100644
--- a/src/cli/System.go
+++ b/src/cli/System.go
@@ -1,36 +1,35 @@
 package cli
 
 import (
+	"fmt"
 	"os"
 	"runtime"
-
-	"git.akyoto.dev/cli/q/src/log"
 )
 
 // System shows system information.
 func System(args []string) int {
 	line := "%-19s%s\n"
 
-	log.Info.Printf(line, "Platform:", runtime.GOOS)
-	log.Info.Printf(line, "Architecture:", runtime.GOARCH)
-	log.Info.Printf(line, "Go:", runtime.Version())
+	fmt.Printf(line, "Platform:", runtime.GOOS)
+	fmt.Printf(line, "Architecture:", runtime.GOARCH)
+	fmt.Printf(line, "Go:", runtime.Version())
 
 	// Directory
 	directory, err := os.Getwd()
 
 	if err == nil {
-		log.Info.Printf(line, "Directory:", directory)
+		fmt.Printf(line, "Directory:", directory)
 	} else {
-		log.Info.Printf(line, "Directory:", err.Error())
+		fmt.Printf(line, "Directory:", err.Error())
 	}
 
 	// Compiler
 	executable, err := os.Executable()
 
 	if err == nil {
-		log.Info.Printf(line, "Compiler:", executable)
+		fmt.Printf(line, "Compiler:", executable)
 	} else {
-		log.Info.Printf(line, "Compiler:", err.Error())
+		fmt.Printf(line, "Compiler:", err.Error())
 	}
 
 	return 0
diff --git a/src/compiler/Function.go b/src/compiler/Function.go
deleted file mode 100644
index d9e65a3..0000000
--- a/src/compiler/Function.go
+++ /dev/null
@@ -1,35 +0,0 @@
-package compiler
-
-import (
-	"git.akyoto.dev/cli/q/src/arch/x64"
-	"git.akyoto.dev/cli/q/src/asm"
-	"git.akyoto.dev/cli/q/src/os/linux"
-	"git.akyoto.dev/cli/q/src/token"
-)
-
-// Function represents a function.
-type Function struct {
-	Name      string
-	Head      token.List
-	Body      token.List
-	Assembler asm.Assembler
-}
-
-// Compile turns a function into machine code.
-func (f *Function) Compile() {
-	for i, t := range f.Body {
-		if t.Kind == token.Identifier && t.Text() == "print" {
-			message := f.Body[i+2].Bytes
-			f.Assembler.MoveRegisterNumber(x64.SyscallNumber, linux.Write)
-			f.Assembler.MoveRegisterNumber(x64.SyscallArgs[0], 1)
-			f.Assembler.MoveRegisterData(x64.SyscallArgs[1], message)
-			f.Assembler.MoveRegisterNumber(x64.SyscallArgs[2], uint64(len(message)))
-			f.Assembler.Syscall()
-		}
-	}
-}
-
-// String returns the function name.
-func (f *Function) String() string {
-	return f.Name
-}
diff --git a/src/cpu/CPU.go b/src/cpu/CPU.go
deleted file mode 100644
index ea16af0..0000000
--- a/src/cpu/CPU.go
+++ /dev/null
@@ -1,106 +0,0 @@
-package cpu
-
-import "git.akyoto.dev/cli/q/src/register"
-
-// CPU manages the allocation state of registers.
-type CPU struct {
-	All     List
-	General List
-	Call    List
-	Syscall List
-}
-
-// New creates a new CPU state.
-func New() *CPU {
-	// Rather than doing lots of mini allocations
-	// we'll allocate memory for all registers at once.
-	registers := [16]Register{
-		{ID: register.R0},
-		{ID: register.R1},
-		{ID: register.R2},
-		{ID: register.R3},
-		{ID: register.R4},
-		{ID: register.R5},
-		{ID: register.R6},
-		{ID: register.R7},
-		{ID: register.R8},
-		{ID: register.R9},
-		{ID: register.R10},
-		{ID: register.R11},
-		{ID: register.R12},
-		{ID: register.R13},
-		{ID: register.R14},
-		{ID: register.R15},
-	}
-
-	rax := &registers[0]
-	rcx := &registers[1]
-	rdx := &registers[2]
-	rbx := &registers[3]
-	rsp := &registers[4]
-	rbp := &registers[5]
-	rsi := &registers[6]
-	rdi := &registers[7]
-	r8 := &registers[8]
-	r9 := &registers[9]
-	r10 := &registers[10]
-	r11 := &registers[11]
-	r12 := &registers[12]
-	r13 := &registers[13]
-	r14 := &registers[14]
-	r15 := &registers[15]
-
-	// Register configuration
-	return &CPU{
-		All: List{
-			rax,
-			rcx,
-			rdx,
-			rbx,
-			rsp,
-			rbp,
-			rsi,
-			rdi,
-			r8,
-			r9,
-			r10,
-			r11,
-			r12,
-			r13,
-			r14,
-			r15,
-		},
-		General: List{
-			rcx,
-			rbx,
-			rbp,
-			r11,
-			r12,
-			r13,
-			r14,
-			r15,
-		},
-		Call: List{
-			rdi,
-			rsi,
-			rdx,
-			r10,
-			r8,
-			r9,
-		},
-		Syscall: List{
-			rax,
-			rdi,
-			rsi,
-			rdx,
-			r10,
-			r8,
-			r9,
-		},
-	}
-}
-
-// ByID returns the register with the given ID.
-func (cpu *CPU) ByID(id register.ID) *Register {
-	return cpu.All[id]
-}
diff --git a/src/cpu/List.go b/src/cpu/List.go
deleted file mode 100644
index e9234aa..0000000
--- a/src/cpu/List.go
+++ /dev/null
@@ -1,29 +0,0 @@
-package cpu
-
-// List is a list of registers.
-type List []*Register
-
-// FindFree tries to find a free register
-// and returns nil when all are currently occupied.
-func (registers List) FindFree() *Register {
-	for _, register := range registers {
-		if register.IsFree() {
-			return register
-		}
-	}
-
-	return nil
-}
-
-// InUse returns a list of registers that are currently in use.
-func (registers List) InUse() List {
-	var inUse List
-
-	for _, register := range registers {
-		if !register.IsFree() {
-			inUse = append(inUse, register)
-		}
-	}
-
-	return inUse
-}
diff --git a/src/cpu/Register.go b/src/cpu/Register.go
deleted file mode 100644
index b11add9..0000000
--- a/src/cpu/Register.go
+++ /dev/null
@@ -1,39 +0,0 @@
-package cpu
-
-import (
-	"fmt"
-
-	"git.akyoto.dev/cli/q/src/errors"
-	"git.akyoto.dev/cli/q/src/register"
-)
-
-// Register represents a single CPU register.
-type Register struct {
-	ID   register.ID
-	user fmt.Stringer
-}
-
-// Use marks the register as used by the given object.
-func (register *Register) Use(obj fmt.Stringer) error {
-	if register.user != nil {
-		return &errors.RegisterInUse{Register: register.ID.String(), User: register.user.String()}
-	}
-
-	register.user = obj
-	return nil
-}
-
-// Free frees the register so that it can be used for new calculations.
-func (register *Register) Free() {
-	register.user = nil
-}
-
-// IsFree returns true if the register is not in use.
-func (register *Register) IsFree() bool {
-	return register.user == nil
-}
-
-// String returns a human-readable representation of the register.
-func (register *Register) String() string {
-	return fmt.Sprintf("%s%s%v", register.ID, "=", register.user)
-}
diff --git a/src/errors/InvalidDirectory.go b/src/errors/InvalidDirectory.go
deleted file mode 100644
index 90beadd..0000000
--- a/src/errors/InvalidDirectory.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package errors
-
-import "fmt"
-
-// InvalidDirectory errors are returned when the specified path is not a directory.
-type InvalidDirectory struct {
-	Path string
-}
-
-// Error implements the text representation.
-func (err *InvalidDirectory) Error() string {
-	if err.Path == "" {
-		return "Invalid directory"
-	}
-
-	return fmt.Sprintf("Invalid directory '%s'", err.Path)
-}
diff --git a/src/errors/RegisterInUse.go b/src/errors/RegisterInUse.go
deleted file mode 100644
index 27f40a5..0000000
--- a/src/errors/RegisterInUse.go
+++ /dev/null
@@ -1,14 +0,0 @@
-package errors
-
-import "fmt"
-
-// RegisterInUse errors are returned when a register is already in use.
-type RegisterInUse struct {
-	Register string
-	User     string
-}
-
-// Error implements the text representation.
-func (err *RegisterInUse) Error() string {
-	return fmt.Sprintf("Register '%s' already used by '%s'", err.Register, err.User)
-}
diff --git a/src/log/log.go b/src/log/log.go
deleted file mode 100644
index 395f6ab..0000000
--- a/src/log/log.go
+++ /dev/null
@@ -1,14 +0,0 @@
-package log
-
-import (
-	"log"
-	"os"
-)
-
-var (
-	// Info is used for general info messages.
-	Info = log.New(os.Stdout, "", 0)
-
-	// Error is used for error messages.
-	Error = log.New(os.Stderr, "", 0)
-)
diff --git a/src/register/ID.go b/src/register/ID.go
deleted file mode 100644
index bc2fe1c..0000000
--- a/src/register/ID.go
+++ /dev/null
@@ -1,44 +0,0 @@
-package register
-
-import "fmt"
-
-// ID represents the number of the register.
-type ID uint8
-
-const (
-	R0 ID = iota
-	R1
-	R2
-	R3
-	R4
-	R5
-	R6
-	R7
-	R8
-	R9
-	R10
-	R11
-	R12
-	R13
-	R14
-	R15
-	R16
-	R17
-	R18
-	R19
-	R20
-	R21
-	R22
-	R23
-	R24
-	R25
-	R26
-	R27
-	R28
-	R29
-	R30
-)
-
-func (r ID) String() string {
-	return fmt.Sprintf("r%d", r)
-}