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[Computer History Museum]

README files

IBM 1401 Demonstration Programs

Stan Paddock

12/18/2016


Table Of Contents
Program Page
README file for Big Print 2
README file for Lincoln 3
README file for Mandelbrot 3
README file for PIE500 4
README file for prime demo 5
README file for PrintPISymbol 5
README file for Tape Demo 6
Trojan Cards 6



README file for Big Print

Friday, March 13, 2016
Author Ed Thelen

Modifications Stan Paddock

BigPrint is a demonstration program run on the IBM 1401
The input is a series of cards:

The first non-blank card is a date card.
Whatever is in the first 25 columns of this card is considered the date.
January 23, 1987 is as good as 1/23/87.
If the card is blank, the program will read again until it finds a non-blank date card.
This makes it easy to run the program multiple times without re-loading the program.

The second non-blank card and all following non-blank cards are name cards.
The first name can be up to 11 characters.
If the first name is longer than 11 characters, it will be truncated to 11 characters.

The second name can be up to 10 characters.
If the second name is longer than 10 characters, it will be truncated to 10 characters.

The second name starts after the space between the first name and the start of the second name.
The next 10 characters will be displayed as the second name.
There can be three names like Juan el Capitan
The program will print Juan on the first line and El Capitan on the second line.
Except that there must be a space between names, the rest of the spacing does not matter.
All extra spaces will be ignored.

Unlike in the past, the date card and the EOF card will be directed
into the second stacker pocket along with the guest name cards.

The last card is the End Of File card.
It is defined as EOF in columns 1-3.
If the three characters EOF are found in Columns 1-3, the program will terminate with a halt.

If you want to run it again with a new set of cards, set sense switch G on,
place the date, name and EOF cards in the reader and press start.

If you don't want to run it again, leave sense switch G off and when you press start,
it will look for and read in the next program.

If you want to run the program and have it wait for more name cards, do the following:

  1. Run the program as normal with a date card and name cards.
  2. Do not add an EOF card
  3. Put two blank cards after the last name card.
  4. The machine will stop after processing the last name card.
  5. Do not clear out the reader.
  6. When you have more name cards, place them in the hopper followed by two blank cards.
  7. Press any START
  8. Go to step 4.
  9. To terminate the program, feed it an EOF card followed by two or more blank cards.


README file for Lincoln

Friday, March 06, 2015
Author  Ron Mak
******************************************************************
     *  LINCOLN'S BIRTHDAY PROGRAM
     *      BY RONALD MAK
     *
     *  ORIGINAL VERSION: FEBRUARY 1969
     *  RESURRECTED:      FEBRUARY 2005
     *  CONDENSED:        NOVEMBER 2010
******************************************************************
This program was written by a very young Ronald Mak.

It prints out the head of Lincoln using the words from the Gettysburg address.

The program will terminate with a halt.
If you want to run it again, set sense switch G on and press start.

If you donít want to run it again, leave sense switch  G off and when you press start, 
it will look for and read in the next program.

README file for Mandelbrot

Saturday, March 07, 2015
Author    Ken Shirriff

Benoit B. Mandelbrot was a Polish-born, French and American mathematician, 
noted for developing the field of fractal geometry, which included coining 
the word "fractal". He later discovered the Mandelbrot set of intricate, 
never-ending fractal shapes, named in his honor.

This program generated the most famous Mandelbrot figure on a machine 
developed 20 years before Fractals were identified.

The IBM 1401 does not have the ability to work with floating point numbers 
so all of the math  has to be done with  integer math.
The program is CPU time intensive but fun to watch if you know what is 
going on in the program.

The program will terminate with a halt.
If you want to run it again, set sense switch G on, and press start.

If you donít want to run it again, leave sense switch G off and when 
you press start, it will look for and read in the next program.

README file for PIE500

PIE500 uses the non-scientific workings of the IBM 1401 to calculate 
   the value of Pi to 500 places.
Author: Ed Thelen

README file for Powers of two
Saturday, March 07, 2015
Author Stan Paddock

Powers Of 2 is a demonstration program run on the IBM 1401 computer.

The IBM 1401 stores one digit per memory location.
The IBM 1401 has 16,000 locations of memory.
With this amount of memory, the IBM 1401 can add together two 8,000 digit numbers.!

Modern computers perform integer arithmetic using binary values.
For the IBM PC, the largest value is 64 bits. 
The largest value that can be expressed in 64 bits is  18,446,744,073,709,551,616.
That is 20 digits long.

The Powers Of Two program demonstrates the ability of the IBM 1401 to handle 
large numbers by starting with a single digit of 2 and then double it until 
it fills a single print line on the IBM 1403 printer.

In addition of that, the program prints out how you pronounce the resultant number.

The program will terminate with a halt.
If you want to run it again, set sense switch G on, and press start.

If you donít want to run it again, leave sense switch G off and when you press start, 
it will look for and read in the next program.

README file for prime demo

Friday, March 06, 2015
Author Ken Shirriff

prime_demo is a demonstration program run on the IBM 1401
It uses the sieve of Eratosthenes an ancient algorithm for finding all prime numbers 
up to any given limit. 

For this program, the given limit is 25,000 due to the memory limitation 
of the computer.

The program will terminate with a halt.
If you want to run it again with a new set of cards, set sense switch G on, 
clear the card reader, place the second date, name and EOF cards in the reader 
and press start.

If you donít want to run it again, leave sense switch  G off and when you press start, 
it will look for and read in the next program.

README file for PrintPISymbol

Friday, March 06, 2015
Author  Ron Mak
******************************************************************
     *  PRINT THE PI SYMBOL
     *      BY KEN SHIRRIFF
     *
     *  ORIGINAL VERSION: JUN 21, 2015
     *  
******************************************************************

This program  prints out the head of Lincoln using numbers of PI. 

The program will terminate with a halt.
If you want to run it again, set sense switch G on and press start.

If you donít want to run it again, leave sense switch  G off and when you press start, 
it will look for and read in the next program.

README file for Tape Demo

Friday, March 10, 2015
Author Stan Paddock

Tape Demo is a demonstration program run on the IBM 1401 computer.

The IBM 1401 uses tapes to store large amounts of data.
When processing that data, the each active tape drive would randomly be 
selected and read or write data.

This program makes the tape drives appear to be working very hard.
The program supports the use of one, two, three or four tape drives.
When a tape drive is selected, 1 to 9 records are written to the drive.
After a half a reel of tape has been written to the tape drives, the 
tape drives go into high-speed rewind. (*)

The program uses the IBM 1401 sense switches to control the actions of the program.
SENSE SWITCH A  = (NOT USED)
SENSE SWITCH B  = TAPE DRIVE  1 ONLY
SENSE SWITCH C  = TAPE DRIVES 1 & 2   
SENSE SWITCH D  = TAPE DRIVES 1 & 2 & 3  
SENSE SWITCH E  = TAPE DRIVES 1 & 2 & 3 & 4
SENSE SWITCH F  = TERMINATE PROGRAM  
SENSE SWITCH G  = RERUN PROGRAM FROM START  
     
The program will terminate with a halt.
If you want to run it again, set sense switch G on, and press start.
(*) If sense switch G is on while the program is running, it will not do the final rewind.
The next time the program runs, all active tape drives will go into high speed rewind.

If you donít want to run it again, leave sense switch G off and when you press start, 
it will look for and read in the next program.

Trojan Cards

 All of the programs in this release have two Trojan cards in front of the actual deck.
These cards do nothing except to protect the real cards of the program deck.
You should have at least two Trojan cards in front of each program deck. 
Every Trojan card is the same and works for any program.
If a Trojan card gets destroyed, toss it away.
If there is another Trojan card on the program deck, go ahead and run the program.
When you are done, add a Trojan card to the front of the program deck


End Of Document