diff --git a/zepa.go b/zepa.go
index 454aa31..3926540 100644
--- a/zepa.go
+++ b/zepa.go
@@ -63,17 +63,39 @@ type Machine struct {
 	registers map[Register]uint32
 }
 
-func (m *Machine) add(inst Instruction) {}
+func (m *Machine) mv(inst Instruction) {
+	m.registers[inst.rd] = uint32(inst.addrConst)
+}
 
-func (m *Machine) sub(inst Instruction) {}
+func (m *Machine) add(inst Instruction) {
+	m.registers[inst.rd] = m.registers[inst.rs1] + m.registers[inst.rs2]
+}
 
-func (m *Machine) cmp(inst Instruction) {}
+func (m *Machine) sub(inst Instruction) {
+	m.registers[inst.rd] = m.registers[inst.rs1] - m.registers[inst.rs2]
+}
+
+func (m *Machine) cmp(inst Instruction) {
+	if m.registers[inst.rs1] == m.registers[inst.rs2] {
+		m.registers[sr] = 0
+	} else if m.registers[inst.rs1] > m.registers[inst.rs2] {
+		m.registers[sr] = 1
+	} else {
+		m.registers[sr] = 2
+	}
+}
 
-func (m *Machine) jump(inst Instruction) {}
+func (m *Machine) jump(inst Instruction) {
+	m.registers[pc] = uint32(inst.addrConst)
+}
 
-func (m *Machine) load(inst Instruction) {}
+func (m *Machine) load(inst Instruction) {
+	m.registers[inst.rs1] = uint32(inst.addrConst)
+}
 
-func (m *Machine) store(inst Instruction) {}
+func (m *Machine) store(inst Instruction) {
+	m.memory[inst.addrConst] = byte(m.registers[inst.rs1])
+}
 
 func (m *Machine) fetch() {
 	var completeInstruction uint32 = 0
@@ -158,14 +180,15 @@ func (m *Machine) decode() Instruction {
 	return m.decodeITypeInst(instruction)
 }
 
-func (m *Machine) execute(inst Instruction) {}
+func (m *Machine) execute(inst Instruction) {
+	inst.opcode(m, inst)
+}
 
 func (m *Machine) boot() {
 	for {
 		m.fetch()
 		decodedInstruction := m.decode()
 		m.execute(decodedInstruction)
-		break
 	}
 }
 
diff --git a/zepa_test.go b/zepa_test.go
index 39cff06..871da12 100644
--- a/zepa_test.go
+++ b/zepa_test.go
@@ -4,6 +4,8 @@ import (
 	"testing"
 )
 
+// To-do: refact to avoid duplicate code
+
 func TestFetch(t *testing.T) {
 
 	machine := NewMachine(2048)
@@ -23,9 +25,7 @@ func TestFetch(t *testing.T) {
 	}
 }
 
-// To-do: refact to avoid code duplication
 func TestDecode(t *testing.T) {
-
 	machine := NewMachine(2048)
 	machine.memory[0] = 0b00110100
 	machine.memory[1] = 0b01000011
@@ -51,3 +51,68 @@ func TestDecode(t *testing.T) {
 		t.Errorf("Expected funct7 to be 0, but got %d", decodedInstruction.funct7)
 	}
 }
+
+func TestMV(t *testing.T) {
+	machine := NewMachine(2048)
+	inst := Instruction{opcode: (*Machine).mv, rd: w0, addrConst: 0xFF}
+	machine.execute(inst)
+
+	if machine.registers[w0] != 0xFF {
+		t.Errorf("Expected w0 to be 42, got %d", machine.registers[w0])
+	}
+}
+
+func TestADD(t *testing.T) {
+	machine := NewMachine(2048)
+	machine.registers[w1] = 66
+	machine.registers[w2] = 3000
+	inst := Instruction{opcode: (*Machine).add, rd: w0, rs1: w1, rs2: w2}
+	machine.execute(inst)
+
+	if machine.registers[w0] != 3066 {
+		t.Errorf("Expected w0 to be 3066, got %d", machine.registers[w0])
+	}
+}
+
+func TestSUB(t *testing.T) {
+	machine := NewMachine(2048)
+	machine.registers[w1] = 30
+	machine.registers[w2] = 10
+	inst := Instruction{opcode: (*Machine).sub, rd: w0, rs1: w1, rs2: w2}
+	machine.execute(inst)
+
+	if machine.registers[w0] != 20 {
+		t.Errorf("Expected w0 to be 20, got %d", machine.registers[w0])
+	}
+}
+
+func TestJUMP(t *testing.T) {
+	machine := NewMachine(2048)
+	inst := Instruction{opcode: (*Machine).jump, addrConst: 0xA}
+	machine.execute(inst)
+
+	if machine.registers[pc] != 0xA {
+		t.Errorf("Expected pc to be 10, got %d", machine.registers[pc])
+	}
+}
+
+func TestLOAD(t *testing.T) {
+	machine := NewMachine(2048)
+	inst := Instruction{opcode: (*Machine).load, rs1: w1, addrConst: 256}
+	machine.execute(inst)
+
+	if machine.registers[w1] != 256 {
+		t.Errorf("Expected w1 to be 256, got %d", machine.registers[w1])
+	}
+}
+
+func TestSTORE(t *testing.T) {
+	machine := NewMachine(2048)
+	machine.registers[w1] = 65
+	inst := Instruction{opcode: (*Machine).store, rs1: w1, addrConst: 100}
+	machine.execute(inst)
+
+	if machine.memory[100] != 65 {
+		t.Errorf("Expected memory value to be 65, got %d", machine.memory[100])
+	}
+}