Data Types and Variables

Implicit Types

Data types in Csound 6 and earlier were declared one of the characters i, k, a, S, w as first character of the variable name. This applied for local variables which are only valid in the scope of an instrument. For global variables these type specifiers were prefixed by the g character.

Local	Global	Data type	Updated at	Examples
i	gi	number	initalization (i-rate)	`iFreq` `giTable`
k	gk	number	control cycle (k-rate)	`kAmp` `gkCount`
a	ga	number	audio sample (a-rate)	`aOut` `gaReverb`
S	gS	string	i-rate or k-rate	`S_file` `gS_host`
f	gf	spectral	k-rate	`fSig` `gfSig`
w	-	spectral (old)	k-rate	-
i[]	gi[]	array	i-rate	`iArr[]` `giArr[]`
k[]	gk[]	array	k-rate	`kArr[]` `gkArr[]`

Explicit Types

In Csound 7 the data type can be given explicitely, without being bound to the name.

nchnls  =   2
0dbfs   =   1

instr 1
  freq:i = 442
  amp:k = linen:k(1,.1,p3,.1)
  sine:a = poscil:a(.2,freq)
  outch(1,sine*amp)
  dB@global:i = -6
  env@global:k = linseg(1,p3,0)
  tri@global:a = vco2(.3,200)
endin
schedule(1,0,3)

instr 2
  outch(2,tri*ampdb(dB)*env)
endin
schedule(2,0,3)

Constants and Reserved Symbols

Constants are available continuously and do not change in value. Usually they are connected with reserved symbols and written in the orchestra header:

sr = 44100
ksmps = 64
0dbfs =  1
nchnls = 2

Expressions

Expressions may be composed to any depth. Each part of an expression is evaluated at its own proper rate. For instance, if the terms within a sub-expression all change at the control rate or slower, the sub-expression will be evaluated only at the control rate; that result might then be used in an audio-rate evaluation. For example, in

k1 + abs(int(p5) + frac(p5) * 100/12 + sqrt(k1))

the 100/12 would be evaluated at orch init, the p5 expressions evaluated at note i-time, and the remainder of the expression evaluated every k-period. The whole might occur in a unit generator argument position, or be part of an assignment statement.