PRINT AT - PLOT - display file converter
J. Waterman, 9 September 2020

This is a short(ish) program that I found I needed when trying to grab data from the display file and dump it elsewhere. For instance, for any given PRINT AT position, what are the eight addresses for the eight rows in the display file, and what address are the attributes held at?

I didn't have such a program, so I wrote it, with a lot of fiddling around with a spreadsheet. It also has PLOT positions thrown in for good measure.

Input PRINT AT coordinates (including the use of rows 22 and 23, i.e. the INPUT area) and the program returns the range of PLOT values in that square, the eight addresses for the display file, and the attribute address. PLOT coordinates will not be given for the INPUT area.

Input PLOT coordinates and the program returns the PRINT AT square the pixel is located in, the eight addresses for the display file, the attribute address, and a POKE for the display file that will insert a pixel at that position. Note that multiple pixels on the same row will require the values for the POKE to be added together - but you all know how the display file works, don't you?

Input a display file address and the program will first check to see if it is where pixels or attributes are stored. The program returns the PRINT AT coordinates, the PLOT range for that square, all eight display file addresses for that square, and - if the input is in the pixel range - the attribute address.