Const MAX_INK As Integer = 5

Type Printer
    ID As Integer
    Ink As Integer
    Backup As Printer Ptr
    Mutex As Any Ptr
End Type

Dim Shared Reserve As Printer
Dim Shared Main As Printer

Reserve.ID = 2
Reserve.Ink = MAX_INK
Reserve.Backup = 0
Reserve.Mutex = Mutexcreate()

Main.ID = 1
Main.Ink = MAX_INK
Main.Backup = @Reserve
Main.Mutex = Mutexcreate()

Dim Shared As String*44 humpty(3) = { _
"Humpty Dumpty sat on a wall.", "Humpty Dumpty had a great fall.", _
"All the king's horses and all the king's men", _
"Couldn't put Humpty together again." }

Dim Shared As String*26 goose(7) = {"Old Mother Goose", "When she wanted to wander,", _
"Would ride through the air", "On a very fine gander.", "Jack's mother came in,", _
"And caught the goose soon,", "And mounting its back,", "Flew up to the moon." }

Sub PrintLine(Byref p As Printer, Byval linea As String)
    Mutexlock(p.Mutex)
    If p.Ink = 0 Then
        If p.Backup = 0 Then
            Mutexunlock(p.Mutex)
            If p.ID = 1 Then
                Print "      Humpty Dumpty out of ink!"
            Elseif p.ID = 2 Then
                Print "      Mother Goose out of ink!"
            End If
            Mutexunlock(p.Mutex)
        Else
            PrintLine(*p.Backup, linea)
        End If
    Else
        Print p.ID; ": "; linea
        p.Ink -= 1
    End If
    Mutexunlock(p.Mutex)
End Sub

Sub HumptyDumpty(Param As Any Ptr)
    For i As Integer = 0 To Ubound(humpty)
        PrintLine(Main, humpty(i))
    Next
End Sub

Sub MotherGoose(Param As Any Ptr)
    For i As Integer = 0 To Ubound(goose)
        PrintLine(Main, goose(i))
    Next
End Sub

' Create threads
Dim HumptyThread As Any Ptr = Threadcreate(@HumptyDumpty, 0)
Dim GooseThread As Any Ptr = Threadcreate(@MotherGoose, 0)

' Wait for threads to finish
Threadwait(HumptyThread)

Sleep