I'm currently checking out options for doing a little coding on a #MSX1 system (real and emulated, when abroad). There's an adapted #F83 #Forth here (https://github.com/janaite/msx-forth83/tree/master) but while it's working, it's not optimized for 40 colum mode. And on MSX1 you only have 40 columns.

Then there's a #BASIC compiler from the former, dutch "#MSX #Club #Gouda" named #Mozart which compiles your MSX BASIC code and gives you some speed improvement - it's here (https://download.file-hunter.com/Program%20language/Mozart%20-%20Compilador%20BASIC%20para%20MSX%20(1990)(Cibertron%20Software)(br).zip).

And, of course there's #TurboPascal3 for MSX which does support 40 column mode (run TINST.COM to set up screen). It's also here (https://download.file-hunter.com/Program%20language/Turbo%20Pascal%203.01a.DSK.zip)

Aside from that you could use a C compiler like #SDCC or #BDSC under #MSXDOS1 ...

Since I do net yet have any sort of mass-storage device for my physical #MSX machine, I set up a 360KB disk drive in #OpenMSX and am now testing the dutch #WBASS2 #Assembler which I put on a #MSXDOS1 formatted disk (image).

So here I am, raw writing to the #TMS9918A video port (the "AAAAA" output).