nargin, nargout

They can be used inside a function body, as shown below.

function [x,y] = goo(a,b,c)   
   print(nargin)   
   print(nargout)   
   x=a+b   
   y=b+c
end

They can also be used outside, for example:

function [y1, y2, y3] = foo(x1, x2)
      y1=x1;      
      y2=x2;      
      y3=x1+x2;
end

nargin('foo')
nargout('foo')

This will return 2 and 3.

In case the function take advantage of the ability to pass (or get) variable numbers of input (or output) to a function, nargin and nargout return negative values. For example :

function [y1, y2, varargout] = goo(x1, varargin)
      y1=x1;      
      y2=x2;      
      y3=x1+x2;
end 

nargin('goo')
nargout('goo')

This will return -2 and -3.