Leonard H. Tower, Jr.

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Leonard H. Tower Jr.
Len Tower.jpg
Len Tower wearing League for Programming Freedom and "No Smoking" badges (c. 1996)
Born (1949-06-17) June 17, 1949 (age 66)
Queens, New York, U.S.
Nationality American
Alma mater MIT
Occupation Free software activist

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.

Academic career[edit]

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]

GNU project[edit]

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 a 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]

League for Programming Freedom[edit]

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]

See also[edit]


  1. ^ a b Puzo, Jerome E., ed. (February 1986). "Gnu's Zoo". GNU'S Bulletin (Free Software Foundation) 1 (1). Retrieved 2007-08-11. 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. 
  2. ^ a b Stallman, Richard M. (24 April 1988), "Contributors to GNU CC", Internals of GNU CC (PDF), Free Software Foundation, Inc., p. 7, retrieved October 3, 2011, 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. 
  3. ^ Heuer, Karl, ed. (July 1997). "GNU's Who". GNU's Bulletin (Free Software Foundation, Inc.) 1 (23). Retrieved October 9, 2011. 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. 
  4. ^ "Award for free software kicks off 'One world, one net' conference". 28 October 1998. Retrieved 18 September 2011. 
  5. ^ The Tech MIT student newspaper masthead, 15 February 1972, page 4.
  6. ^ Goldstein, Stacey; Chassell, Robert J.; Tower, Jr., Leonard, eds. (February 1988). "GNU's Who". GNU's Bulletin (Free Software Foundation, Inc.) 1 (4). Retrieved October 4, 2011. 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). 
  7. ^ Tuttle, Jonathan P.; Chassell, Robert J.; Tower Jr., Len, eds. (January 1997). "GNU's Who". GNU's Bulletin (Free Software Foundation) 1 (22). Retrieved October 4, 2011. 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. 
  8. ^ Rubin, Paul, ed. (June 1987). "GNU's Who". GNU's Bulletin (Free Software Foundation) 1 (3). Retrieved October 4, 2011. 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. 
  9. ^ a b Stallman, Richard (September 20, 2011). "About the GNU Project". The GNU Project. Retrieved October 9, 2011. 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. 
  10. ^ Richard M. Stallman (forwarded by Leonard H. Tower Jr.) (March 22, 1987). "GNU C compiler beta test release". Newsgroupcomp.lang.c. Retrieved October 9, 2011. 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. 
  11. ^ Stallman, Richard M. (2001) "Contributors to GCC," in Using and Porting the GNU Compiler Collection (GCC) for gcc version 2.95 (Cambridge, Mass.: Free Software Foundation)
  12. ^ Mike Haertel (November 12, 1988). "Re: Implications of recent virus (Trojan Horse) attack". Newsgroupcomp.unix.wizards. Retrieved October 4, 2011. I am a college student. Also the author of GNU grep, coauthor of GNU diff, and working on GNU sort  line feed character in |quote= at position 76 (help)
  13. ^ David S. Hayes (August 19, 1993). "Re: Shareware (My Experience)". Newsgroupcomp.sys.mac.apps. Retrieved October 5, 2011. I wrote some of the original code in the GNU "diff" program. (It has since been replaced by other code.) 
  14. ^ Myers, Eigene W. (1986). "An O(ND) Difference Algorithm and Its Variations" (PDF). Algorithmica 1 (2): 251–266. doi:10.1007/BF01840446. Retrieved October 4, 2011. 
  15. ^ Bob Page (November 19, 1989). "v89i217: rcs - revision control system, Part02/14". Newsgroupcomp.sources.amiga. Retrieved October 4, 2011. GNU DIFF was written by Mike Haertel, David Hayes, Richard Stallman and Len Tower. 
  16. ^ "analyze.c", diffutils-2.7, Free Software Foundation, Inc., October 2, 1994, retrieved October 4, 2011, 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."  line feed character in |quote= at position 103 (help)
  17. ^ Tower, Leonard H., et al. (2001) "AUTHORS" file, revision 1.3, GNU diff and patch utilities (Cambridge, Mass.: Free Software Foundation)
  18. ^ Smallwood, Kevin C. (30 December 1991) "Updated BOF Schedule for San Francisco USENIX Conference," comp.org.usenix USENET posting;
  19. ^ MacPhee, Spike R. (November 1991). "Speaking Volunteers". Programming Freedom (League for Programming Freedom) 1 (1). Archived from the original on 2007-03-10. Retrieved October 4, 2011. 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. 

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