# Sample file showing .mdm file format

# Brief introduction to the "Baby" Mark I:
#
#	The main memory and registers were Williams tubes,
#	capable of representing 32 bits on a line.  The three
#	tubes used in the prototype machine were the A tube
#	(accumulator), C tube (control), and S tube (store).
#	The A tube had a single 32-bit line; the S tube had
#	32 such lines, and the C tube had two: the "control
#	instruction" line (CI) -- "program counter in modern
#	terminology -- and the "present instruction" line (PI).
#
#	Because the CI was incremented at the *beginning* of
#	the fetch/execute cycle, programs would usually start 
#	on line 1, rather than line 0 (a program starting at
#	line 0 would need CI initially to be -1 in order to
#	execute properly).
#
#	The instruction format consisted of a 3-bit op-code
#	and an 13 bit address field (the most significant 16 bits
#	of the instruction word and 8 bits of the address field 
#	were ignored).  Two's complement representation was used 
#	for negative data values.
#
#	    Op code     operation      (original notation)
#	       0           jump              (s, C)
#	       1           relative jump     (c+s, C)
#	       2           load negative     (-s, A)
#	       3           store accumulator (a, S)
#	       4           subtract          (a-s, A)
#	       5           same as 4 (undocumented)
#	       6         ++CI, if a < 0      (Test)
#	       7           stop              (Stop)

# Comments begin with a '#'; blank lines are ignored

# The letter 'A', 'C' or 'S' followed by a colon, specifies
# that the values following are placed in the specified tube.
#
# For example, the following lines put the value -2 into the
# A tube:
A:
01111111111111111111111111111111
#
# Note that, in the spirit of the original Manchester machines,
# all numbers are expressed in "backwards binary", with the
# least significant bit on the left.

# Unspecified tubes or lines will not be touched.
#
# For example, the following lines clear the A tube and
# the CI line, leaving the contents of the PI line and the
# S tube alone.
A:
0	# note that all 32 bits need not be specified
C:	# and that end-of-line comments are allowed
0

# A number after the tube letter specifies the initial line
# at which the values are to be placed.  Any positive integer
# is accepted (modulo the size of the tube).
#
# For example, the following lines place the data values
# 4, 2^18 and -(2^18) in lines 22, 23 and 24 of the S tube.
S22:
001
0000000000000000001
00000000000000000011111111111111