User Defined Opcodes (UDO)

User Defined Opcodes are functions written in Csound code. They are located in the global space of the orchestra code, or loaded in a text file via #include.

The definition of a User Defined Opcode starts with the keyword opcode and ends with the keyword endop. The syntax and implementation of UDOs has changed in Csound 7; so there are two different syntax conventions which can be used.

Old style UDO definition

The implementation is described in detail in the manual page for opcode (link to that page).

New style UDO definition

User Defined Opcodes now follow the syntax opcode name(inargs):(outargs).

opcode myop(inval:i):(i)
  xout(inval+1)
endop

opcode empty():void
  puts("empty!",1)
endop

instr 1
  print(myop(17))
  empty()
endin
schedule(1,0,0

Give example for pass-by-reference as difference to old style UDOs.