Type of variable samples

How can I use a sample as a variable? Which type of variable should I use to do that? For example I want to do this:

instr 1
       
        ifilcod = "pista.wav"
       
        a1,a2 diskin ifilcod, p4

        outs a1, a2

endin

but we have the following error message:

Macro definition for omacro:MacCsound
orch compiler:
31 lines read
        instr 1
error:  input arg '"pista.wav"' of type string not allowed when expecting i, line 12:
        ifilcod = "pista.wav"

1 syntax errors in orchestra.  compilation invalid
-->CsoundLib Terminated...