Editing QIO (section)

=== {{mono|IO$_READPROMPT}} ===

Probably the most complex single QIO request possible is the VMS terminal driver's {{mono|IO$_READPROMPT}} call with the {{mono|IO$M_TIMED}} modifier; this QIO requires all six additional parameters:

; P1 : The address of the buffer into which the input characters are received
; P2 : The length of the buffer, limiting the maximum number of characters to read. If the buffer is filled, the read will complete successfully, even if the user does not type a line-terminator character. Zero is allowed, in which case the read will terminate successfully with zero characters read.
; P3 : The maximum number of seconds to wait for more input. This is only used if the {{mono|IO$M_TIMED}} modifier is present, and a value of zero means zero seconds: the read will terminate immediately, so the only possible input will be whatever had been "typed ahead" by the user.
; P4 : The address of the optional "terminator mask", specifying which ASCII characters terminate the read. If omitted, this defaults to the usual VMS line delimiters including carriage-return (but not line-feed). It is possible to specify a mask with ''no'' line terminators, in which case the read will only complete when the buffer is full, or the timeout has elapsed.
; P5 : The address of a prompt string to be displayed to the user before accepting input. The advantage of providing this prompt, instead of as a prior write operation, is automatic redisplay in any situation requiring a refresh of the input line while the read is in progress (such as after an operator message has been broadcast to the terminal, or the user hits CTRL/R to redisplay the line).
; P6 : The length of the prompt string.

By appropriate choices of the above parameters, it is possible to do both terminal input and output with the one call, there is no need to use the regular {{mono|IO$_WRITEVBLK}} call for terminal output at all.