' Define the opcodes
Enum
    NOP = 0
    LDA
    STA
    ADD
    SUV
    BRZ
    JMP
    STP
End Enum

Function instr_(op As Ubyte, v As Ubyte) As Ubyte
    Return (32 * op) + v
End Function

Function NOP_(v As Ubyte) As Ubyte
    Return instr_(NOP, v)
End Function

Function LDA_(v As Ubyte) As Ubyte
    Return instr_(LDA, v)
End Function

Function STA_(v As Ubyte) As Ubyte
    Return instr_(STA, v)
End Function

Function ADD_(v As Ubyte) As Ubyte
    Return instr_(ADD, v)
End Function

Function SUB_(v As Ubyte) As Ubyte
    Return instr_(SUV, v)
End Function

Function BRZ_(v As Ubyte) As Ubyte
    Return instr_(BRZ, v)
End Function

Function JMP_(v As Ubyte) As Ubyte
    Return instr_(JMP, v)
End Function

Function STP_(v As Ubyte) As Ubyte
    Return instr_(STP, v)
End Function

Sub execute(nombre As String, program() As Ubyte)
    ' Initialize memory and program counter
    Dim As Ubyte m(Ubound(program))
    Dim As Short m_pos = -1

    For i As Ubyte = Lbound(program) To Ubound(program)
        m(m_pos + 1) = program(i)
        m_pos += 1
    Next

    Dim As Boolean running = True
    Dim As Ubyte pc = 0
    Dim As Ubyte a = 0
    Dim As Ubyte op
    Dim As Ubyte operand

    While running
        op = m(pc) \ 32
        operand = m(pc) Mod 32
        pc = (pc + 1) Mod 32

        Select Case op
        Case NOP
            ' No operation
        Case LDA
            a = m(operand)
        Case STA
            m(operand) = a
        Case ADD
            a = (a + m(operand)) Mod 256
            If a > 255 Then a = 0
        Case SUV
            a = (a - m(operand)) Mod 256
            If a < 0 Then a = 255
        Case BRZ
            If a = 0 Then pc = operand
        Case JMP
            pc = operand
        Case Else
            ' Stop
            running = False
            Print Space(12 - Len(nombre)) & nombre & ": " & a
        End Select
    Wend
End Sub

' Test programs
Dim poly1(4) As Ubyte = {LDA_(3), ADD_(4), STP_(0), 2, 2}
execute("2+2", poly1())

Dim poly2(13) As Ubyte = {LDA_(12), ADD_(10), STA_(12), LDA_(11), SUB_(13), STA_(11), BRZ_(8), JMP_(0), LDA_(12), STP_(0), 8, 7, 0, 1}
execute("7*8", poly2())

Dim poly3(0 To ...) As Ubyte = {LDA_(14), STA_(15), ADD_(13), STA_(14), LDA_(15), STA_(13), LDA_(16), SUB_(17), BRZ_(11), STA_(16), JMP_(0), LDA_(14), STP_(0), 1, 1, 0, 8, 1}
execute("fibonacci", poly3())

Dim poly4(0 To ...) As Ubyte = {LDA_(13), ADD_(15), STA_(5), ADD_(16), STA_(7), NOP_(0), STA_(14), NOP_(0), BRZ_(11), STA_(15), JMP_(0), LDA_(14), STP_(0), LDA_(0), 0, 28, 1, 0, 0, 0, 6, 0, 2, 26, 5, 20, 3, 30, 1, 22, 4, 24}
execute("linkedList", poly4())

Dim poly5(0 To ...) As Ubyte = {NOP_(0), NOP_(0), STP_(0), 0, LDA_(3), SUB_(29), BRZ_(18), LDA_(3), STA_(29), BRZ_(14), LDA_(1), ADD_(31), STA_(1), JMP_(2), LDA_(0), ADD_(31), STA_(0), JMP_(2), LDA_(3), STA_(29), LDA_(1), ADD_(30), ADD_(3), STA_(1), LDA_(0), ADD_(30), ADD_(3), STA_(0), JMP_(2), 0, 1, 3}
execute("prisoner", poly5())

Dim poly6(0 To ...) As Ubyte = {LDA_(3), SUB_(4), STP_(0), 0, 255}
execute("0-255", poly6())

Dim poly7(0 To ...) As Ubyte = {LDA_(3), SUB_(4), STP_(0), 0, 1}
execute("0-1", poly7())

Dim poly8(0 To ...) As Ubyte = {LDA_(3), ADD_(4), STP_(0), 1, 255}
execute("1+255", poly8())

Sleep