Written in 1976, Microsoft BASIC for the 8 bit MOS 6502 has been available for virtually every 6502-based computer. Also for the SBC’s on this site: KIM-1, SYM-1, AIM 65 and as a port of Applesoft on the Apple 1.

Binary versions and manuals are on the pages dedicated to these machines:

• KIM-1
• SYM-1
• AIM 65
• Apple 1 Replica’s

Sources of early Microsoft Basic on 6502 are available on pagetable blog by Michael Steil

• Original source for a cross assembler on a PDP-10
• Disassembled from dumped binaries, commented and assembled and linked to 100% original binaries

Build binaries from source on a Linux system (Raspberry PI OS)

First install CC65 package, the assembler and linker are required.

You need the CC65 package, a C and Macro assembler and linker for the 6502.

https://github.com/cc65/wiki/wiki is broken, https://cc65.github.io/getting-started.html is fine.

git clone https://github.com/cc65/cc65.git
cd cc65
make
sudo make avail

Now get the MS Basic source and assemble the binaries

https://github.com/mist64/msbasic
git clone https://github.com/mist64/msbasic
cd msbasic
./make.sh
cd tmp
ls

and you will see a directory of binaries (.bin), symbol table (.lbl) and object files (.o)

Compare the binary files with the binary files in the msbasic/orig folder and you will see hopefullyy they are identical!

It is not only nice to see the source, now you are able to customize a Microsoft Basic to your likings.

Steps as advised in the pagetable description:
1. Create a .cfg file by copying an existing one.
2. Adapt the make file for the new target.
3. Change the platform specific source files

and assemble again.

For example, the KB9 Basic can be changed:

• Character in//out to a serial device
• Control-C handler update
• Remove the ROR workaround
• Save/load to another storage device
• See the KIM Kenner articles for patches on KB9 Basic

An example is this post by Gordon Henderson who made a serial interfaced Commodore Basic by creating a new variant and tweaking some conditionals, replacing the screen editor with the line editing interface of older versions.

KB-9 stands for Microsoft Basic V1.1 for the KIM-1  with 9 digits precision. .
Scanned manual
The original KIM-1 KB9 Microsoft Basic V1.1, audio wave, binary and papertape format