Because it could complete the three usual steps ("compile-link-go") in just one pass, the system became popular for teaching students computer programming.
The Fortran language had been developed at IBM, but suffered from slow and error-prone three-stage batch processing workflow.
Their programs were generally short, but usually contained logic and syntax errors, resulting in time-consuming repetition of the steps and confusing "core dumps" (It often took a full day to submit and receive the successful or failed output from the computer operator).
[3] In summer 1965, four undergraduate students of the University of Waterloo, Gus German, James G. Mitchell[4][5] Richard Shirley and Robert Zarnke, led by Peter Shantz, developed a Fortran compiler for the IBM 7040 computer called WATFOR.
[6] This simple, one-step process allowed non-experienced programmers to learn programming with lower cost in time and computing resources.
[7] To aid in debugging, the compiler uses an innovative approach to checking for undefined variables (an extremely common mistake by novice programmers).
[8] The project members, Betty Schmidt, Paul Dirksen, Paul H. Cress, Lothar K. "Ned" Kesselhut, Bill Kindree and Dereck Meek, were later joined by Mike Doyle, Rod Milne, Ron Hurdal and Lynn Williams, completed 360 WATFOR in the early part of 1967.
As a result of proposals from the SHARE user group Fortran committee and others, a new version called WATFIV was produced in 1968.
People involved with maintenance and enhancement included Bernie Murphy, Martin Wiseman and Yvonne Johnson.
In 1974, a compiler with characteristics similar to the IBM implementation was created for the Digital Equipment Corporation PDP-11 computer and called WATFOR-11.
The team members, Jack Schueler, Jim Welch and Terry Wilkinson, were later joined by Ian McPhee who had added new control statements to the WATFIV compiler for structured programming (SP).
The original SP features were later enhanced with additional statements by Bruce Hay in WATFIV-S in 1980 and by Jack Schueler in WATFOR-11S in 1981.
Under the leadership of Jack Schueler, Watcom employees and undergraduate students from the University of Waterloo's Co-operative Computer Science program became involved in the creation of the WATFOR-77 compiler.
The major work was done by Geno Coschi, Fred Crigger, John Dahms, Jim Graham, Jack Schueler, Anthony Scian and Paul Van Oorschot.
Most of the execution-time support (undefined variable checking, subscript evaluation, intrinsic functions) was written in assembly language for good performance.
This project included Geno Coschi, Fred Crigger, Tim Galvin, Athos Kasapi, Jack Schueler, Terry Skomorowski and Brian Stecher.
During the summer of 1985, a project was started to adapt WATFOR-77 to the Digital Equipment Corporation VAX computer series running the VMS operating system.
As late as 1995, classes for programming in WATFIV were still being held at the University of Mississippi, led by Professor Charles H. (Chuckie) Franke.