a variable, which keeps standard input and standard output (file descriptor)
%io(1)
%io(2)
%io(1) returns standard input (file descriptor 5).
%io(2) returns standard output (file descriptor 6).
File descriptor 0 is the standard error.
`mfprintf`_(%io(2),'Scilab stdout (C)');
`mfprintf`_(0,'Scilab stderr (C)');
`write`_(%io(2),'Scilab stdout (Fortran)');
`write`_(0,'Scilab stderr (Fortran)');
[units,typ,names]=`file`_()