path: root/baremetal/ex2.subx

# Test out the video mode by filling in the screen with pixels.
#
# To build a disk image:
#   ./translate_subx_baremetal baremetal/ex2.subx    # emits disk.img
# To run:
#   qemu-system-i386 disk.img
# Or:
#   bochs -f baremetal/boot.bochsrc  # boot.bochsrc loads disk.img
#
# Expected output:
#   html/baremetal.png

== code

main:
  # ecx <- start of video memory
  8b/-> *0x7f28 1/r32/ecx

  # eax <- final pixel of video memory
  8d/copy-address *(ecx + 0x0bffff) 0/r32/eax  # 0xbffff = 1024*768 - 1

  # for each pixel in video memory
  {
    39/compare %eax 1/r32/ecx
    7c/jump-if-< break/disp8
    # write its column number to it
    88/byte<- *eax 0/r32/AL
    48/decrement-eax
    eb/jump loop/disp8
  }

  # hang indefinitely
  {
    eb/jump loop/disp8
  }