Elliot 803 Simulator - Using Algol 60

New!! Algol Pre-loaded

The latest version comes with the Algol tapes pre-loaded. The 803 had ferrite core storage, which (normally) retains data when switched off. Elliotts would never guarantee this, but it was often worth trying, and quite often worked OK. The simulator now pre-loads a core image into the simulated core store before completing its startup procedures. You can therefore skip much of the stuff below. To enter the pre-loaded compiler, you have to set the keyboard buttons to 40 7 (that F1=40, N1=7=4+2+1) then 'read','operate','normal','operate' after loading the Algol source program in the reader. You can then continue from here.

If your program is too large and overwrites the compiler (as the 'COGS' does!) then you will get a message 'RELOAD TAPES 1 AND 2' when the program finishes. From there you have the choice of following the procedure below, or pressing the 'reload' button on your browser. This restarts the simulator and reloads the compiler image, but sadly also destroys any programs you have created!

Loading the Compiler from tapes

This is a simple recipe for compiling and running Algol 60 programs on the 803 Simulator. It doesn't cover all the details of Elliott Algol 60 language or all of the operating instructions. For this you will need a copy of the Elliott publication '803 ALGOL' which covers both aspects in full detail. I hope to be able to publish a copy of this on my web pages, but I am still awaiting permission from the copyright holders....

There are two programs in the filing cabinet, in the drawer marked Test Programs. One is in the box labelled 'Algol Test Program' and is a very simple Algol 60 program which illustrates a simple loop and output statements. The second is a more complex program that takes a while to run, and uses paper tape input from a data tape, and involves much more calculation and careful formatting of the output.

Before you can compile an Algol program, you must first load the Compiler and Run-time System from paper tape. This takes a while, indeed, the simulator currently takes longer than the original computer to do this, so be prepared to wait a while.

First load up the first tape, which is in the drawer marked 'Algol', in the box labelled 'Tape 1'. There is just the one tape, so transfer it to the reader as described in the general handling page. Next enter the initial instructions by setting F1=40, N1=0, press Read, Operate, Normal, Operate in sequence, and the Busy and Overflow lights on the keyboard will flicker. You may like to switch to the Reader again and watch the tape jump around as it is read in. It will gradually shrink in diameter until eventually it will halt.

Remove the tape from the reader by pressing the Runout button, upper right on the reader, which transfers the tape back to your hand, neatly wound up (most unrealistic if you have ever had to rewind paper tapes!). Put the tape back in it's box, close it and open the box labelled 'Tape 2'. Pick that up and transfer it to the reader, switch back to the Keyboard and perform the operation described in the Elliott documentation as 'change the sign digit'. This means the F1=40 button. If this is the first time through, it will be depressed at this point, so press the RED F1 button which will realease it. The computer will then start loading the second tape. Again, this takes some time, though a bit less than Tape 1 as it is somewhat smaller.

When it has stopped, put the tape back into it's box, close the box and the drawer, and open the bottom drawer, labelled 'Test Programs'. Open the box marked 'Algol Test Program' and transfer the small tape from there to the reader.

Switch back to the keyboard and 'change the sign digit', which should now mean press down the button marker 40 on the F1 row. The program tape will be read in, and the program is compiled into store. Switch to the 'Printer' page and, provided no errors have occurred, the computer should print out the program title, followed a 'FREE STORE' message and several line feeds.

Running Programs that have succesfully compiled

At this point the system is waiting to run the program and for this a new technique is needed. Again, it involves the keyboard, but this time it is the 40 bit of F2 that needs to be changed. Press down this button and the program will start to run, printing out numbers on the Console Printer. After a few lines of output the system displays an 'END OF PROGRAM' message and the system returns to the point where it expects another program source tape to be loaded. If you wish to do so you can then load a further program, and continue by changing the sign digit.

If you try to compile the program from the 'Cogs Program' box, you will see that this is a much larger program, and takes a little longer to compile. This program also expects a data tape, which is the smaller of the two tapes in the box. You can use the right mouse button to display the titles of tapes. Click a second time to cancel the display.

Load the data tape into the reader before changing the 40-button on F2. The program displays a fair amount of output on the console printer and eventually, after several long pauses, displays a final answer and terminates.

If you want to try preparing your own program tapes you will need to learn how to use the tape editor. Click here to learn how to use it.


Page created by Bill Purvis, last update 29th November, 2004