XXX  Names: GTOS, BOSS, PROMPT/COMMAND, MINIDOS, ...
XXX  CardBoot -> Find load and run a GT1 file
XXX  Dir -> Builtin command. Only names
XXX  List -> External command: file size, date, volume label
XXX  Cls -> Clear terminal
XXX  Stat ->
XXX  Type -> command (consider passing of ARGS)
XXX  Device letters or not? A: B: C:
        Familiary, goes back to before CP/M
XXX  Directories or not?
XXX  Switches or not

        CardBoot.gcl
                [Loads from ROM, lives $8a0...up]
                Checks SD card and FAT32
                Can find and load one file: GTOS.gt1
                May use application specificic SYS functions

        GTOS.gt1 -- Basic operating system services (BOSS)
                                                "CP/M BOOT"
                Welcome message (throw-away code in $500)
                  CLS + "GTOS v1 32K" + Apple II beep
                  Load and execute Command.gt1
                Provide resident services in $200..$4f9
                - BOSS.writeByte                "CP/M CONOUT"
                - BOSS.readByte                 "CP/M CONIN"
                - BOSS.setDevice                "CP/M SELDSK"
                - BOSS.readDir/find/enter/delete/create
                - BOSS.loadFile -- Gt1 loading
                - BOSS.readSector               "CP/M READ"
                - BOSS.writeSector              "CP/M WRITE"
                - BOSS.command                  "CP/M WBOOT (DOS COMMAND.COM)"
                - BOSS.spawn
                - BOSS.launch
                - Won't be reloaded during a session
                - Controls all shadow memory. May hide in banked memory
                - Can use generic SYS functions, but not app-specific
                - Can be be replaced without EPROM change

                API:
                - Use fixed addresses, but only few (esp. zero page) --> function codes
                -

        Command.gt1 -- Command parser and dispatcher
                Lives in top..$7fff
                Display OK/error, this unifies error reporting
                Show prompt and cursor symbol
                  A> _
                Handle user input with line editing
                Built-in command: Change device letter
                Built-in command: Dir
                Find file '<CMD>' in root dir
                If not found, return to prompt
                Find argument files, open if found?
                Load first sector of file in $500..$6ff
                If not a command -> BOSS.Launch
                If command, loadFile and run? Or defer
                  to command itself

        <CMD>.gt1:
                Do stuff with BOSS
                Exit:
                        Big program -> BOSS.prompt
                        Small program -> RET

        Launch.gt1:
                Escapes GTOS
                Stand-alone loading from bottom of visible screen area, like Loader
                Requirements: compatible with Tetronis, Apple-1, MSBASIC
                Reset terminal, video etc
                Fast loading GT1 file -> sectors must be split