diff --git a/src/build/asm/Assembler.go b/src/build/asm/Assembler.go
index 9fe9229..e3341a3 100644
--- a/src/build/asm/Assembler.go
+++ b/src/build/asm/Assembler.go
@@ -91,6 +91,18 @@ func (a *Assembler) Finalize() ([]byte, []byte) {
 				code = x64.MoveRegisterRegister64(code, operands.Destination, operands.Source)
 			}
 
+		case POP:
+			switch operands := x.Data.(type) {
+			case *Register:
+				code = x64.PopRegister(code, operands.Register)
+			}
+
+		case PUSH:
+			switch operands := x.Data.(type) {
+			case *Register:
+				code = x64.PushRegister(code, operands.Register)
+			}
+
 		case RETURN:
 			code = x64.Return(code)
 
diff --git a/src/build/asm/Instructions.go b/src/build/asm/Instructions.go
index 04de2ea..4856d1e 100644
--- a/src/build/asm/Instructions.go
+++ b/src/build/asm/Instructions.go
@@ -24,6 +24,16 @@ func (a *Assembler) RegisterRegister(mnemonic Mnemonic, left cpu.Register, right
 	})
 }
 
+// Register adds an instruction using a single register.
+func (a *Assembler) Register(mnemonic Mnemonic, register cpu.Register) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: mnemonic,
+		Data: &Register{
+			Register: register,
+		},
+	})
+}
+
 // Label adds a label at the current position.
 func (a *Assembler) Label(name string) {
 	a.Instructions = append(a.Instructions, Instruction{
diff --git a/src/build/asm/Mnemonic.go b/src/build/asm/Mnemonic.go
index 95fc2a2..77dbf81 100644
--- a/src/build/asm/Mnemonic.go
+++ b/src/build/asm/Mnemonic.go
@@ -11,6 +11,8 @@ const (
 	MUL
 	LABEL
 	MOVE
+	POP
+	PUSH
 	RETURN
 	SUB
 	SYSCALL
@@ -40,6 +42,12 @@ func (m Mnemonic) String() string {
 	case MUL:
 		return "mul"
 
+	case POP:
+		return "pop"
+
+	case PUSH:
+		return "push"
+
 	case RETURN:
 		return "return"
 
diff --git a/src/build/asm/Register.go b/src/build/asm/Register.go
new file mode 100644
index 0000000..a618370
--- /dev/null
+++ b/src/build/asm/Register.go
@@ -0,0 +1,15 @@
+package asm
+
+import (
+	"git.akyoto.dev/cli/q/src/build/cpu"
+)
+
+// Register operates with a single register.
+type Register struct {
+	Register cpu.Register
+}
+
+// String returns a human readable version.
+func (data *Register) String() string {
+	return data.Register.String()
+}