Apple Personal LaserWriter NTR Spezifikationen PDF herunterladen (Seite 59)

CHAPTER 4

Communication Channels

Status Queries and Spontaneous Messages

Typically, characters written to the standard output ﬁle by PostScript operators such as

are not sent immediately. They are buffered until a flush is executed. A flush

occurs automatically

■

at the end of a job

■

in interactive mode, whenever the user is prompted to make an entry

IMPORTANT

If a PostScript language program writes data that is needed

immediately by the host, for example, a reply to an environmental

query, it is important to ﬂush after writing the data. Otherwise, a

deadlock may occur.

▲

Status Queries and Spontaneous Messages 4

The Personal LaserWriter 320 printer provides a status query facility that enables the

host or user to determine what the printer is doing. The printer responds to a status

query asynchronously with respect to normal job execution. That is, it sends a response

immediately, regardless of what has gone on before or how much input data has been

buffered. This facility primarily enables spoolers (printer control programs) to track the

activities of the Personal LaserWriter 320 printers under their control.

If the printer receives a Control-T character from the active input channel, it replies with

a one-line status message over the active port’s output channel. The message is

bracketed by the text sequences

%%[

and

]%%

, to enable the host software to extract the

message from the ordinary data generated by the job being executed.

The status message has standardized syntax that is intended to be machine readable. It

consists of one or more key value pairs, separated by semicolons—for example:

%%[job: Jane’s report; status: busy; source: LocalTalk ]%%

The possible keys, values, and meanings are as follows:

job

The name of the job is stored as

jobname

entry in

statusdict

(see

Chapter 3). This ﬁeld is omitted if the current job has not deﬁned

jobname

status

Indicates what the printer is currently doing:

✖

■

idle

indicates no job is in progress

busy

means the printer is executing the user’s PostScript

language program

waiting

means that the I/O is waiting in the middle of a job

printing

indicates that the printer is printing and that paper is

in motion

PrinterError:

reason

means that there is a printer error such

as a paper jam or printer out of paper

initializing

indicates the printer is starting up

source serial

parallel

, or

LocalTalk

indicates the source of the job

that the server is currently executing (this ﬁeld is omitted if the

server is idle)

1 2 ... 54 55 56 57 58 59 60 61 62 63 64 65 66

Kommentare zu diesen Handbüchern

Keine Kommentare

Apple Personal LaserWriter NTR Spezifikationen Seite 59

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Drucken & Scannen Apple Personal LaserWriter NTR