TP3/FREEDOS-CALC.md

Running CALC.COM under FreeDOS in QEMU

This is the manual FreeDOS route. The supported, tested path remains shell/tests/calc_cli.py, which boots the compiler's own bootcom.s loader.

1. Build CALC.COM

From the repository root:

cd shell

# Build comtest (also runs the normal COM tests).
tests/run_com_tests.sh

# Stage CALC.PAS with CALC.INC beside it.
tests/calc_ladder.sh

# Compile the staged source.  comtest writes CALC.PAS.COM in the cwd.
printf '%s\n' ../tmp/calc_ladder/CALC.PAS | ./comtest
mv -f CALC.PAS.COM CALC.COM

If a fresh CALC.PAS.COM is already present, cp CALC.PAS.COM CALC.COM is enough.

2. Make a FAT floppy image containing CALC.COM

sudo apt install qemu-system-x86 mtools unzip

cd /tmp
dd if=/dev/zero of=calc.img bs=1024 count=1440
mformat -i calc.img -f 1440 ::
mcopy -i calc.img /path/to/TP3-comp/shell/CALC.COM ::CALC.COM
mdir -i calc.img ::

mdir must show CALC.COM.

3. Boot the FreeDOS 1.4 LiveCD

Download and unpack:

mkdir -p ~/freedos
cd ~/freedos
wget https://download.freedos.org/1.4/FD14-LiveCD.zip
unzip FD14-LiveCD.zip

Boot qemu:

qemu-system-i386 \
  -m 128 \
  -boot d \
  -cdrom ~/freedos/FD14LIVE.iso \
  -drive file=/tmp/calc.img,format=raw,if=floppy \
  -vga std

At the FreeDOS menu choose Use FreeDOS 1.4 in Live Environment mode.

At the DOS prompt, the LiveCD may take A:, so check both drives:

DIR A:
DIR B:

In the tested layout A: is the FreeDOS boot floppy and the CALC floppy is B::

B:
CALC

4. Persistent installation

Create a hard-disk image and boot the installer:

qemu-img create -f raw ~/freedos.img 128M
qemu-system-i386 -m 128 -hda ~/freedos.img \
  -cdrom ~/freedos/FD14LIVE.iso -boot d

Install to C:, then reboot with both disks attached:

qemu-system-i386 -m 128 -hda ~/freedos.img \
  -drive file=/tmp/calc.img,format=raw,if=floppy -boot c

Inside FreeDOS:

COPY A:\CALC.COM C:\CALC.COM
C:
CALC

Verified under FreeDOS

Tested under the FreeDOS 1.4 LiveCD in qemu: CALC shows the welcome screen, starts the spreadsheet, evaluates 1+2 as 3.00, opens the command menu and quits through /Q. The same build is expected to work in DOSBox-X because both use the standard DOS INT 21h AH=02h convention: the character is in DL.

That convention was the garbage-screen bug. The runtime originally put output characters only in AL, because the project's private bootcom.s handler read AL; real DOS reads DL. The runtime now sets both, and bootcom.s has been changed to the DOS convention so the harness can no longer hide a future divergence.

The tested project launcher remains:

cd shell
python3 tests/calc_cli.py --com CALC.PAS.COM \
  --no-keypress --keys '\r1+2\r/Q'