Software Preservation Group of the Computer History Museum

History of FOCAL (Formula Calculator)

Bruce Ray, editor - Bruce@Wild-Hare.com - Wild Hare Computer Systems Inc.

Last modified 26 December 2024

Rick Merrill, circa 1968

"... I took an editor, a floating point package and the specs for the JOHNNIAC Open Shop System (JOSS) and ideas from the Massachusetts General Hospital Utility Multi-Programming System (MUMPS) and wrote an interpreter that would do the user's job on the spot and interactively. This program became known as Formula Calculator (FOCAL)." - Rick Merrill

 

 

FOCAL - The Beginning

"Back in Maynard I took an editor, a floating point package and the specs for the JOHNNIAC Open Shop System (JOSS) and ideas from the Massachusetts General Hospital Utility Multi-Programming System (MUMPS) and wrote an interpreter that would do the user's job on the spot and interactively.

I remember thinking that I wanted a single letter for each command not only for the simple branch table but also for debugging. I did not want to have to remember an octal code for each command but to be able to see in the code the letter itself that DDT could display. I eschewed pre-compiling as a waste of time.

I gathered the code for the editor and the floating point package (probably developed by Henry Burkhart) and got them to assemble together eliminating duplicate symbols and other bookkeeping issues. This was the top-down stage. Then I realized that my branch tables used full word addresses and would therefor flow across the page ends, wasting no space because of local page sizes. So I began coding from the bottom-up stage with SORTJ, PUSHJ, POPJ, ETC.

I acquired the "JOSS Apologetica" which was really helpful in distinguishing the commands so that there was no overlap. Then I found that the semicolon could fore-shorten commands in generally useful ways. Adding buffered interrupts came later and made a huge difference.

This program became known as Formula Calculator (FOCAL)." [Rick Merrill 2024]

Development Timeline

Year Description
1968Initial FOCAL release (for PDP-8)
1969FOCAL, 1969 release (for PDP-8)
1971FOCAL available on all commercial DEC machines (PDP-5/7/8/9/10/11/12/15)
Nova 800 running PDP-8 emulator running FOCAL 69 at Data General booth at FJCC (Las Vegas)
1977Intel 8080-based systems
MOS Technology 6502-based systems
1978DEC VAX computers
1980Texas Instruments TI-990
2000 and
beyond		 Ports for any machine with a 'C' compiler (i.e. micros, IBM 360/370, .etc)

Materials from Developer

Rick Merrill's 2024 CHM Donations

Rick Merrill has donated his original FOCAL archives to the Computer History Museum and made PDF reproductions available for downloading here. Donated items include computer listings, marketing literature, client comments.

Of particular significance are Rick's personal notes and the first FOCAL manual.

 

 

Personal Documents

Technical Documents

Listings

Marketing

Interesting Mentions

Resources

Other implementations

Acknowledgments

Thanks to Rick Merrill, Paul McJones, and the proprietors of all the web sites linked to above.