Asynchronous Terminals and Printer Processes Programming Manual

PROCEDURE CALLS FOR ACCESSING TERMINALS

WRITEREAD

The WRITEREAD procedure ensures that the computer is ready to

receive data from a terminal immediately after a message is

written to a terminal. This is useful when conversationally

prompting a terminal user for input.

For example, to prompt a terminal user with a colon (:) and then

wait for input, use the following code in your program. Only one

buffer, TERM^BUFFER, is specified; the data is returned there.

TERM^BUFFER := ": "; ! specify the prompt character

CALL WRITEREAD (HOME^TERM^NUM, TERM^BUFFER, 1, 72, NUM^READ);

The WRITEREAD call displays a colon on the terminal and then

waits for input. Note that WRITEREAD does not issue a carriage

return/line feed character sequence to the terminal after the

write phase of the WRITEREAD.

The WRITEREAD procedure is useful for issuing control commands

to a terminal. For example, to read a seven-character cursor

address from a terminal that requires a control character

sequence of "<ESC> a <DC1>" (an escape character, followed by

lowercase letter "a," followed by a DC1 character), you could

include the following code:

TERM^BUFFER ':=' [ %015541, %010400 ]; ! "ESC a DC1"

CALL WRITEREAD ( HOME^TERM^NUM, TERM^BUFFER, 3, 7, NUM^READ );

After the WRITEREAD, TERM^BUFFER contains the cursor address, and

seven is returned to NUM^READ.

AWAITIO

Operations with terminals require human response and, therefore,

can take an indefinite period of time. Use the

time-limit

parameter to ensure that a terminal operator performs an opera-

tion within a specified period of time. The terminal must have

been opened to permit nowait I/O.

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