Currently, the spark pen seems to go wrong at least once a month. A possible cause of this is the voltage level used, which is high. DEC will look into this and have agreed to supply a spare pen from Reading in the event of failure.
It seems that a likely cause of the trouble is the speed of response, and a delay may well solve the problem. DEC are looking to see if a modification for a PDP8, which delays the keyboard, could be used on the PDP15. Neil Parker is working with DEC on this problem.
The question of fuses for this device has again been raised, and DEC are looking into the rating required for such fuses. The transistors burnt out again twice and were replaced. Moving some of the transistors in the pre-amplifier has a marked effect on screen characteristics and there may be some loose joints there.
Neil has discovered that we can connect the currently acquired Tektronix to the PDP15 via the LT19, with the addition of a LT19B board (one required for each device), and a LT19C board to give the correct interface. It would be necessary to recompile the DOS LT handler to take account of the extra device, and provide some routines to drive it, but it is not expected that this will involve much effort. JRG will get a quote for the two boards.
The routines to read region limits have been incorporated.
While experimenting with Wipe and In-betweening, some problems with the existing implementation have arisen.
At the moment, the same pointers are used both to read and write a file. A file may not be defined within another file; but by suitably manipulating local priorities, it is possible to DRAW a file during a definition. This causes a clash of pointers, so a separate set of storage pointers will be used.
The routine LCPRY sets the local priority of the next display routine which has not any built-in local value. This priority is reset at the end of that routine. However, when using TEXT, and requiring the storage of the relative orders themselves, it is not possible to insert LCPRY calls between each call of DRAW. Hence it is proposed that local priority be reset by the FIDF at the end of the file being defined.
XPOS, YPOS hold the current position in terms of the co-ordinates of the region selected. Changing the region does not alter the values in XPOS, YPOS, but will, of course, alter the 'absolute' position in terms of the base region. It is thus necessary to use some absolute order such as SETXY in the new region to fix the position. This is not always convenient, but the alternative (alter XPOS, YPOS when REGION is called to refer to the same 'absolute' position) would involve two searches down the region chain. The point is noted.
It is felt that a new user manual should be issued later in the Autumn.
As GEORGE 4 Mk 7 appears to have plenty of Executive problems of its own, we will not press for BSI tests until August. If, however, ICL feel able to begin testing earlier, so much the better.
No new large coding projects will take place for the time being. Instead, a number of small cleaning-up jobs will be undertaken, and a film of SPROGS begun. The programming of this film should highlight the areas in which we must concentrate effort to help the film-maker.
