#
# FILE: factorial.bca
#

#
# N.B. ".bca" suffix means "byte-code assembler"
#

#
# Assembler code for computing factorials.
#
# Register contents:
#
# 0 -- count
# 1 -- result
#

#
# We want to compute factorial(10).
# First load 10 into register 0 and load 1 into register 1.
#

  push  10
  store 0
  push  1
  store 1

#
# Put the counter value on the stack.  If it's 0, we're done
# and register 1 contains the final result.
#

1 load  0   # The "1" is a label.
  jz    2

#
# Every time through the loop, we compute:
#

# result = result * count

  load  1       # result
  load  0       # count
  mul
  store 1       # new result

# count  = count - 1

  load  0
  push  1
  sub
  store 0

# Go back and loop until done.

  jmp   1

# When we get here, we're done.

2 load  1       # Put the result value on the stack.  The "2" is a label.
  print         # Print it to stdout.
  stop          # Stop the program.