An online simulation of the SSEM is presented here. The simulator contains several pre-loaded programs ready to run, including that first stored program.

The switches and controls provided on the simulation are intended to match the functioning of those of the original machine, however the layout does not presume to match the original. The original machine had only one monitor tube with a three-position switch to select what was being monitored, the simulation provides three monitors for convenience.

Using the simulation

• The simplest procedure for using the simulation is to click on the 'PROGRAMS' box and select a program. This loads the program into the memory. Pressing the 'EXEC' button begins execution. Single-stepping is accomplished by flipping the 'RUN/STOP' switch to 'STOP', then repeatedly pressing the 'EXEC' button.
• More help is provided within the simulation in the form of roll-over descriptions of the the various switches and elements.

Simulator Assembly Language

Assembler instructions for the simulator take the form:

   loc-line: operation-code operand-line [--comment]
   loc-line: NUM decimal-number [--comment]
   loc-line: BINS binary-number [--comment]
   loc-line: BNUM binary-number [--comment]

For example:

 02: STO 31  -- put A in line 31

The BINS (binary instruction) and BNUM (binary number) commands assign binary values to lines in the store. These are used for programs which use the Store as an "image" or X-Y display and allow the unused bits in instructions to be set. The motivation for having BINS in addition to BNUM is for the sake of the disassembler output in the simulator display.