The timed input mode employs a disk file containing line images of commands and functions that the user wishes executed at specific LST or UT times. The first six columns of each line image contain the time of execution in format hhmmss (it is important that the times be right justified so that the units of seconds is always in column six). The keywords and functions contained in these lines are processed sequentially, as rapidly as they can be executed. When data-taking program activations are encountered, the system goes into a "wait state" until the routine has finished, then the line processing continues.
To enter the timed command mode, the user enters the UTC or LST to specify whether the times are to be interpreted according to Universal time or Local Sidereal time respectively. If the keyword UTC or LST is entered with no arguments, then processing begins with the first line image whose time is after the present time. If, on the other hand, a time in the appropriate format follows LST or UTC , then processing begins with the line image at that time. Upon entry into this mode, the flag "TIMED INPUT-LST" or "TIMED INPUT-UTC" appears at the top of screen 1, as well as the time of the next line image to be processed (or the time of the line image currently being processed). Care must be taken in scheduling line images so that data- taking routines do not extend beyond the next line image's start time. If this should happen, the tracking programs will attempt to catch up by processing the line images whose times were bypassed.