prompt
    OpenVMS usage:character string
    type:         string descriptor
    access:       read only
    mechanism:    by reference
    A string that must begin with "cr,lf". For example, to produce
    the standard user name prompt, use your language equivalent of
    the following BLISS value:
     UPLIT(12,UPLIT BYTE(CR,LF,'Username: '))
    Declare the string in C using the following statement:
    $DESCRIPTOR(<variable_name>, "lrlnUsername:")
    You then pass the descriptor using the variable name.
    This routine also produces the standard user name prompt if you
    pass the value 0 for this argument.