The results from a number of platforms do seem consistent. There is one other test which would be extremely helpful to confirm. You mention the case when you set the second parameter to zero. I tend to assume that you used ONE zero character, i.e. "<ESC>[TOP;0r" where TOP was the upper line number. My question is what occurs if you use THREE zero characters for the second parameter, i.e. "<ESC>[TOP;000r" since that would help quite a bit if I want to support previous versions of some emulators which do not support the scrolling range command correctly. In that case, the user could patch the file to be whatever the number of lines on the screen actually is without having to expand the number of characters allocated for that second parameter JUST in case the screen has more than 99 lines. In fact, TOP should also have THREE characters with leading ZEROs as well just in case. I realize that this means repeating each test again, but assuming that THREE character parameter values with leading zeros are acceptable, it would make the programming a lot easier. I tend to assume that three characters are always OK since the maximum number of columns for most screens is 132 characters and the common firmware to parse parameters would always need to be able to handle up to three characters including with embedded zeros, so leading zeros could be handled in the same manner and should not need anything special - if the subroutine is coded the way that seems most reasonable - not that anyone outside of the firmware manufacturer would ever see that code. Your mention of the VT510 with 48 lines is also EXTREMELY interesting. I think that the VT420 also has that capability. I have made a few enhancements to KED under RT-11 which now supports emulated terminals up to 255 columns by 255 lines, although not both at the same time. No one seems to be at all interested, but it has been very helpful in my case since E11 supports these emulated screen sizes. My justification and naming for the new KED variant is K42 after the VT420. Since there are two other KED variants, K52 and K62, each respectively for the VT52 and VT62 real DEC terminals, the K42 name seemed appropriate. I would hope that at least a few individuals are reading this thread who might still using RT-11 or TSX-Plus. The new K42.SAV has code to run under TSX-Plus without needing to INSTALL the program under TSX-Plus (with special handling parameters) as KED must be. It would seem that DEC went only so far in supporting the TSX-Plus operating system in that nothing prevented running KED under TSX-Plus, but S&H had to add extra EMTs and RUN options to support features which are handled very differently in RT-11. Jerome Fine