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Leonard H. Tower Jr. | |
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![]() Len Tower wearing League for Programming Freedom and "No Smoking" badges (c. 1996) | |
Born | New York City, U.S. | June 17, 1949
Alma mater | MIT |
Occupation | Free software activist |
Organizations | Free Software Foundation, League for Programming Freedom |
Leonard "Len" H. Tower Jr. (born June 17, 1949) is a free software activist and one of the founding board members of the Free Software Foundation, [1] where he contributed to the initial releases of gcc [2] and GNU diff. He left the Free Software Foundation in 1997. [3]
Tower was born June 17, 1949, in Astoria, Queens, in New York City, U.S.
In 1971, Tower received an SB in biology from the Massachusetts Institute of Technology. [4] During that time he was business manager at The Tech , the student newspaper. [5]
As the FSF's first full-time paid employee, Tower mostly performed administrative tasks, including managing mailing lists, newsgroups and requests for information. [6] [7] [8]
In 1986, Tower assisted Richard Stallman with Stallman's initial plan to base the C compiler for the GNU Project on the Pastel compiler Stallman had obtained from Lawrence Livermore Lab. [9] Tower worked on rewriting the existing code from Pastel, a variation of Pascal, into C [1] while Stallman worked on building the new C front end. Stallman dropped that plan when he discovered the Livermore compiler required too much memory, concluding, "I would have to write a new compiler from scratch. That new compiler is now known as GCC; none of the Pastel compiler is used in it, but I managed to adapt and use the C front end that I had written." [9] Stallman released his new GNU C compiler March 22, 1987, [10] acknowledging others' contributions, including Tower's, who "wrote parts of the parser, RTL generator, RTL definitions, and of the Vax machine description" based on ideas contributed by Jack Davidson and Christopher Fraser. [2] [11]
Along with Mike Haertel, [12] David Hayes [13] and Stallman, Tower was also one of the initial co-authors of GNU diff, a file comparison utility based on a published algorithm [14] by Eugene Myers. [15] [16] [17]
During the late 1980s and early 1990s, Tower spoke at USENIX conferences as a representative of the FSF. [18]
Tower was an early member of the League for Programming Freedom. Through 1991, Tower was one of the organization's two most active speakers, along with Richard Stallman. [19]
Bash is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell. First released in 1989, it has been used as the default login shell for most Linux distributions. Bash was one of the first programs Linus Torvalds ported to Linux, alongside GCC. A version is also available for Windows 10 and Windows 11 via the Windows Subsystem for Linux. It is also the default user shell in Solaris 11. Bash was also the default shell in versions of Apple macOS from 10.3 to 10.15, which changed the default shell to zsh, although Bash remains available as an alternative shell.
The Free Software Definition written by Richard Stallman and published by the Free Software Foundation (FSF), defines free software as being software that ensures that the end users have freedom in using, studying, sharing and modifying that software. The term "free" is used in the sense of "free speech," not of "free of charge." The earliest-known publication of the definition was in the February 1986 edition of the now-discontinued GNU's Bulletin publication by the FSF. The canonical source for the document is in the philosophy section of the GNU Project website. As of April 2008, it is published in 39 languages. The FSF publishes a list of licences which meet this definition.
GNU is an extensive collection of free software, which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operating systems popularly known as Linux. Most of GNU is licensed under the GNU Project's own General Public License (GPL).
The GNU Compiler Collection (GCC) is an optimizing compiler produced by the GNU Project supporting various programming languages, hardware architectures and operating systems. The Free Software Foundation (FSF) distributes GCC as free software under the GNU General Public License. GCC is a key component of the GNU toolchain and the standard compiler for most projects related to GNU and the Linux kernel. With roughly 15 million lines of code in 2019, GCC is one of the biggest free programs in existence. It has played an important role in the growth of free software, as both a tool and an example.
The GNU Debugger (GDB) is a portable debugger that runs on many Unix-like systems and works for many programming languages, including Ada, Assembly, C, C++, D, Fortran, Go, Objective-C, OpenCL C, Modula-2, Pascal, Rust, and partially others.
The GNU Compiler for Java (GCJ) is a discontinued free compiler for the Java programming language. It was part of the GNU Compiler Collection.
The GNU Project is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and computing devices by collaboratively developing and publishing software that gives everyone the rights to freely run the software, copy and distribute it, study it, and modify it. GNU software grants these rights in its license.
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Free Software Foundation (FSF) grants two annual awards. Since 1998, FSF has granted the award for Advancement of Free Software and since 2005, also the Free Software Award for Projects of Social Benefit.
Robert "Bob" Chassell was one of the founding directors of the Free Software Foundation (FSF).
Brian Jhan Fox is an American computer programmer and free software advocate. He is the original author of the GNU Bash shell, which he announced as a beta in June 1989. He continued as the primary maintainer of bash until at least early 1993. Fox also built the first interactive online banking software in the U.S. for Wells Fargo in 1995, and he created an open source election system in 2008.
Alternative terms for free software, such as open source, FOSS, and FLOSS, have been a controversial issue among free and open-source software users from the late 1990s onwards. These terms share almost identical licence criteria and development practices.
Richard Matthew Stallman, also known by his initials, rms, is an American free software movement activist and programmer. He campaigns for software to be distributed in such a manner that its users have the freedom to use, study, distribute, and modify that software. Software that ensures these freedoms is termed free software. Stallman launched the GNU Project, founded the Free Software Foundation (FSF) in October 1985, developed the GNU Compiler Collection and GNU Emacs, and wrote all versions of the GNU General Public License.
Linux is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which includes the kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name "GNU/Linux" to emphasize the importance of GNU software, causing some controversy.
gNewSense was a Linux distribution, active from 2006 to 2016. It was based on Debian, and developed with sponsorship from the Free Software Foundation. Its goal was user-friendliness, but with all proprietary and non-free software removed. The Free Software Foundation considered gNewSense to be composed entirely of free software.
GNU Emacs is a free software text editor. It was created by GNU Project founder Richard Stallman, based on the Emacs editor developed for Unix operating systems. GNU Emacs has been a central component of the GNU project and a flagship project of the free software movement. Its name has occasionally been shortened to GNUMACS. The tag line for GNU Emacs is "the extensible self-documenting text editor".
The GNU General Public License is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general use and was originally written by the founder of the Free Software Foundation (FSF), Richard Stallman, for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. These GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. It is more restrictive than the Lesser General Public License and even further distinct from the more widely used permissive software licenses BSD, MIT, and Apache.
The GNU Free Documentation License is a copyleft license for free documentation, designed by the Free Software Foundation (FSF) for the GNU Project. It is similar to the GNU General Public License, giving readers the rights to copy, redistribute, and modify a work and requires all copies and derivatives to be available under the same license. Copies may also be sold commercially, but, if produced in larger quantities, the original document or source code must be made available to the work's recipient.
The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed under copyleft terms, such as with its own GNU General Public License. The FSF was incorporated in Boston, Massachusetts, US, where it is also based.
Alexandre "Alex" Oliva, is a Brazilian free software activist, developer, former vice president of the board of directors of the Free Software Foundation (FSF) and founding member of Free Software Foundation Latin America (FSFLA). He is currently on-hold from his PhD studies at the Institute of Computing of the State University of Campinas, Brazil whilst working as a compiler engineer at Red Hat, contributing in the GCC compiler. He is the maintainer of Linux-libre, a fork of the Linux kernel which removes non-free software components, such as binary blobs from the kernel. The Linux-libre kernels are used in Linux distributions such as Parabola GNU/Linux-libre, gNewSense, and Trisquel, all of which are recommended by the Free Software Foundation and the GNU Project.
First ... there's Richard Stallman. ... Secondly there's Leonard H. Tower, Gnu's teddy bear. Len is Gnu's first and so far only paid full time employee. Gnu's Hawk, Robert Chassell ... [and] Professor Hal Abelson and Professor Geral Sussman ... round out FSF's board of Directors ... Although I have a portable C and Pascal compiler, ... most of the compiler is written in Pastel, ... so it must all be rewritten into C. Len Tower, the sole full-time GNU staff person, is working on this, with one or two assistants.
The idea of using RTL and some of the optimization ideas came from the U. of Arizona Portable Optimizer, written by Jack Davidson and Christopher Fraser. ... Leonard Tower wrote parts of the parser, RTL generator, RTL definitions, and of the Vax machine description.
Carol Botteron, Robert J. Chassell, Tami Friedman, Peter H. Salus, and Len Tower Jr. have left the FSF. Tami continues to volunteer for GNU as our Administrivia Coordinator. We thank them for their hard work.
Richard Stallman continues to do countless tasks, including refining the C compiler, GDB, GNU Emacs, etc. ... Finally, Len Tower continues to handle electronic administrivia (mailing lists, information requests, and system mothering).
Volunteers Phil Nelson and Len Tower work on our Web site. Len also remains our online JOAT (jack-of-all-trades), for mailing lists, gnUSENET newsgroups, information requests, etc.
Richard Stallman ... is currently continuing to develop the GNU C compiler. Hackers Len Tower, Richard Mlynarik, and Paul Rubin are doing various pieces of volunteer work as their time permits it, and Jay Fenlason continues to work full time on the GNU assembler and libraries.
Hoping to avoid the need to write the whole compiler myself, I obtained the source code for the Pastel compiler, which was a multiplatform compiler developed at Lawrence Livermore Lab. It supported, and was written in, an extended version of Pascal, designed to be a system-programming language. I added a C front end, and began porting it to the Motorola 68000 computer. But I had to give that up when I discovered that the compiler needed many megabytes of stack space, and the available 68000 Unix system would only allow 64k. ... I concluded I would have to write a new compiler from scratch. That new compiler is now known as GCC; none of the Pastel compiler is used in it, but I managed to adapt and use the C front end that I had written.
The GNU C compiler is now available for ftp from the file /u2/emacs/gcc.tar on prep.ai.mit.edu. This includes machine descriptions for vax and sun, 60 pages of documentation on writing machine descriptions ... the ANSI standard (Nov 86) C preprocessor and 30 pages of reference manual for it. This compiler compiles itself correctly on the 68020 and did so recently on the vax. It recently compiled Emacs correctly on the 68020, and has also compiled tex-in-C and Kyoto Common Lisp.
I am a college student. Also the author of GNU grep, coauthor of GNU diff, and working on GNU sort
I wrote some of the original code in the GNU "diff" program. (It has since been replaced by other code.)
GNU DIFF was written by Mike Haertel, David Hayes, Richard Stallman and Len Tower.
The basic algorithm is described in: "An O(ND) Difference Algorithm and its Variations", Eugene Myers, Algorithmica Vol. 1 No. 2, 1986, pp. 251-266; see especially section 4.2, which describes the variation used below."
I run the speaker bureau. Richard M. Stallman and Len Tower have done the bulk of our speaking engagements to date, but cannot be everywhere at once. Our cloning attempts, despite Richard's views on copying, have not yet succeeded. We would like more volunteers, with or without previous experience, to speak to people around the world and inform them about the software look-and-feel and patent issues.