Home > Articles > Programming

Happy 15th Birthday to Tcl and the Tk Toolkit

Tcl and the Tk Toolkit is 15 years old! To celebrate the success of John Ousterhout's book, we've asked people in the Tcl/Tk community to comment on how the book has affected their lives as programmers.

Look for the second edition of Tcl and the Tk Toolkit, which is publishing later this year but is now available as a Rough Cut.

Like this article? We recommend

Like this article? We recommend

In celebration of the 15th birthday for John Ousterhout’s book,Tcl and the Tk Toolkit, we've asked some Tcl/Tk developers, members Tcl Core Team, and organizers of the 16th Annual Tcl/TK Conference to share their thoughts on John Ousterhout’s language and his book, including what they were doing in 1994, when they first used Tcl/Tk, what kind of development they you use Tcl/Tk for, what part of Tcl and the Tk Toolkit was most valuable to them.

We've asked David Korn, creator of the Korn Shell; Donal K. Fellows of the University of Manchester; Ron Fox, a senior physicist at the National Superconducting Cyclotron Laboratory at Michigan State University and author of a data analysis tool called SpecTcl; and Michael McLennan, author of Effective Tcl/Tk Programming: Writing Better Programs with Tcl and Tk and senior research scientist at Purdue University, to comment on John's book. Their answers to our questions are posted, below.

To take you back, here's what else what going on in our world in 1994:

  • Nancy Kerrigan was attacked one month before Winter Olympics; Tonya Harding later banned from skating competition for her role
  • Bill Clinton and Boris Yeltsin sign the Kremlin Accords
  • Commodore Computer files for bankruptcy
  • Tcl and the Tk Toolkit, written by John Ousterhout, was published by Addison-Wesley
  • Marc Andreesan and Jim Clark launch Mosaic Communications. Later that year they release Netscape Navigator browser
  • The movie Forrest Gump is released, and later wins Oscar for Best Picture
  • Whitney Houston releases album, The BodyGuard, which later wins Grammy for album of the year
  • Television show Friends premieres
  • Jerry Yang and Dan Filo launch Yahoo!

What you were doing in 1994?

David Korn: I was finishing the book for the new KornShell, ksh93.

Donal K. Fellows: That was the year I graduated and got my first job.

Ron Fox: I was employed as a ‘Senior Physicist’ for the National Superconducting Cyclotron Laboratory at Michigan State University. The title is very misleading. What a I did then and now is create, and maintain software for online data acquisition and analysis from experiments run at our facility. See http://www.nscl.msu.edu for more information.

When did you first use Tcl/Tk?

Donal K. Fellows: While I first encountered in in 1993 or 1994 (I don't know which, sorry to say) I first *used* it in spring 1995 (April?) after picking up a copy of _Tcl and the Tk Toolkit_.

Ron Fox: I can’t recall exactly when but it must have been after 1993.

Michael McLennan: I started using Tcl/Tk when I joined AT&T Bell Labs in 1992 to create graphical user interfaces for semiconductor device/process simulation tools that we developed in house. One of my first projects was to create an interactive editor/simulator for the metallization layers of an integrated circuit—much like the application that I later developed which appears on the front cover of John’s book. I couldn’t believe how quickly my first project came together! In just 2 weeks, I had a fully functional interactive drawing editor (based on the Tk canvas) which fed cross sections to an interconnect capacitance simulator. It was a religious experience for me, and I’ve been hooked on Tcl/Tk ever since.

For what kind of development did you use Tcl/Tk for?

David Korn: My son Jeff merged ksh93 and Tcl/Tk to create tksh which uses the tk library.>

Donal K. Fellows: Back then, I used it for building an IDE (for developing and simulating asynchronous CPUs) to replace a previous one written in Common Lisp. The version in Tcl/Tk was faster in all respects and produced much nicer output.

Ron Fox: What I do recall is that the first real Tcl/Tk application was to control a distributed data taking system for the S800 spectrograph at the NSCL . A paper on using Tcl/Tk to implement a group communication systems to control this sort of system had caught my eye (“Dart – Data Acquisition System for the Next Generation of Fermilab Fixed Target Experiments G. Oleynik et al. IEEE Transaction on Nuclear Science Feb. 1994, Vol 41, No 1 pg. 45). The paper was presented at the 1993 IEEE Conference on Real-Time Computer Applications in Nuclear, Particle and Plasma Physics in Vancouver June 8-11 1993 which I had attended. I had the idea of doing something similar, and wrapping it up in a nice GUI that made it hard for the experimenters to make errors.

This was successful and was used for a few years until we did a re-work of the data taking and data analysis software at the NSCL for the commissioning of the coupled cyclotron and radioactive beam facility. That would have been 2003. In this rework we had the idea of making the data analysis software (now called NSCLSpecTcl) an extended Tcl/Tk Interpreter and exposing this to the users so that they could script their analysis and build their own application specific GUI’s. In 2004 I became aware of the Tcl conferences and presented this work at Tcl 2004 in New Orleans.

Somehow after that I wound up on the program committee for Tcl 2005, and then wound up as the “chair-for-life” of that committee.

Michael McLennan: In 1993, I developed the [incr Tcl] package (support for object-oriented programming) to help the language scale better to support larger and larger projects. The largest application that I developed with Tcl/Tk was a CAD tool called SimVision developed at Cadence Design Systems, Inc., which included about 250,000 lines of Tcl/Tk and 250,000 lines of C/C++.

What part of Tcl and the Tk Toolkit was most valuable to you and why?

Donal K. Fellows: Back then? Absolutely the pages on the canvas widget, as they opened up the door to things I would have found it exceptionally difficult to do any other way.

Ron Fox: Two parts: Part 1: The entire Tk toolkits make writing GUI’s fun not hard. NSCLSpecTcl’s visualizer makes use of a recycled X-11/Motif application that was absolutely no fun to write. Seeing the ease with which physicists who have very little formal training as programmer wrap their applications with sophisticated GUI’s is truly rewarding.

The second part is the ease with which Tcl/Tk can be extended. In evaluating scripting languages for NSCLSpecTcl I had also looked at Python which was coming on strong at the time.. it just seemed so much easier to add commands to Tcl than it was to Python. Further the command line model of Tcl/Tk was something much more familiar to physicists at the time.

Michael McLennan: To me, this blending of Tcl with C/C++ is its real strength—the ability to create “programmable” tools with a customized command language, or to orchestrate C/C++ code at a high level to create a finished application. Tcl established that paradigm for development, and is still the best solution available today for that purpose. For that reason, I think Part III of John’s book—Writing Tcl Applications in C—is the most valuable.

Is there anything else you’d like to say about the language, John, or his book?

David Korn:Tcl/tk was one of the first to successfully merge scripting and gui programming. We owe John our gratitude.

Donal K. Fellows: It is an exceptionally well-written book, but it wasn't until I tried to revise and add to it that I realized the full extent of this. The content of the chapters fit together so well and lead me from being an absolute beginner to the point where I could tackle complex projects. Fitting in with that has been a massive challenge. Generally, I'd say, "Thanks John for helping me learn to be a genuine software engineer rather than just yet another programmer; hope to meet you one day."

Ron Fox: John’s book is still the book I recommend for beginning Tcl/Tk programmers. While it’s out of date with respect to where the language has gone, it is still the clearest exposition of the principles of the language. I’m looking forward to the next revision of the book that I understand is underway and hope the authors will be able to maintain the clarity of John’s original text as they bring it up to date.

Michael McLennan: I always keep a few copies of John’s book on my shelf to hand out to new team members and other colleagues. I’m still using Tcl/Tk today for my latest project, the Rappture toolkit (www.rappture.org), which is an interface builder for scientific simulation and modeling tools. I’ve learned so much in my career by not only using Tcl/Tk, but studying its internals and its design. Thanks to John for a marvelous work of software engineering!

Please share your link to some of your favorite Tcl/Tk code or some comments and thoughts about Tcl/Tk here.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020