The central polling routine in PIGS is working with most of the input devices. The major exception is the DMAC pencil follower. This could be a fault in the hardware interface but is more likely to be a fault in the handler. The one produced by GAE initially did not have the ability to get single character input.
A preliminary test with the photographer when setting up a film of the system for DECUS revealed the problem that the characters at the standard SIZE were virtually unreadable. As others may also require to generate films or slides of the display it seems reasonable to introduce a facility for specifying SIZE 0 characters. The main problem is that the system is set up to allow 9 character names which will have to be reduced to about 5 characters if the larger size is chosen. Also the larger size will mean that less lines are possible on the screen area.
The size of the package has been growing gradually. Loading under DDT it is only just possible to get the complete system into 32 K. It will therefore be necessary to introduce an overlayed structure with all the problems associated with debugging under CHAIN and EXECUTE.
The system for MENU display and updating is now working with the controlling table generated by hand. An assembler which generates the table automatically from a specified block structure format needs to be produced. It would be reasonable to have this fully defined and implemented before the DECUS meeting.
Once the BSI works, it will be necessary to specify the formats to be sent between PIGS and SPROGS. Currently the SPROGS commands are recognised and all that remains is to define the format of the command to be sent to the 1906A. The information returned to the 1906A is currently undefined. The simplest initial format is probably going to be the name of a FOG routine followed by the arguments. This should allow displays to be built up on the PDP15 with very little effort. The final interface is likely to be more complex than this simple version. However it should allow interaction between the 1906A and PDP15 while development continues on PIGS. The likely sequence of work is therefore:-
(1) Implement assembler for automatic MENU generation
(2) Produce basic PIGS/SPROGS interface routines
(3) Overlay PIGS and implement under RSX
(4) Generate more complete form of PIGS/SPROGS interface
With the introduction of a storage tube, it will be necessary to modify the view program to allow output to this instead of the VT04. At this time it may be worthwhile introducing additional facilities. There has been a need to back up to the previous frame for example. Also the command F could have a predefined argument in place of the single frame advance available now. The user would set up a parameter, for example, so that each F caused 10 frames to be skipped.
Digitisation onto tape with no visual feedback is an operation which is prone to error. With the death of ATLAS, there is no automatic means for patching up errors in the digitisation. There is therefore a need for a system whereby the data output from the DMAC is passed and stored in the PDP15 with a visual record on a display of the points that have been digitised. In place of paper tape output it is more convenient to output on 7 track magnetic tape especially if large amounts of data are involved. The system could allow correction of parts of the picture by indicating on the display the. lines or points in error. Facilities similar to those in the ATLAS package would be made available as a stand-alone package or as part of the SPROGS system.
