Delta ADS turns 50
Developing software is looking to the future, but sometimes it is good to turn around and look back.
As we did, we discovered that the foundations of our products were made almost half a century ago.
Delta ADS - Review
This year, 2026, we celebrate 50 years of Delta ADS. In this years newsletters we will look back on the history of Delta ADS and reflect on its features that have contributed to its long lasting success.
Half a century ago, programming a computer was a special kind of magic for most people. It also was an individual and very creative process with pen, paper and punch cards. Getting complex programs functioning correctly was a difficult and time-consuming process and came with considerable costs that did not allow for the compiler to be used for error finding.
The use of terminals to write programs was a big improvement in the development process. It provided a better overview of the program logic without having to compile and print a listing first. This overview was limited of course by the maximum of 24 lines a terminal was able to show at the same time. This was not sufficient for complex decisions which gave rise to the first tools to support the programming. Although such tools were available for many programming languages, the main field for these tools was in the area of the most widely used programming language for business applications: COBOL.
1971: The First Idea
In 1971, Dr Reinhold Thurner of Zürich University published about the use of decision tables in the software development which led to DETAB/GT to generate the programming code based on a more abstract definition language . By 1976 DETAB/GT reached 100 installations, the same amount of installations was achieved by its competitor VORELLE2.
Generating a complex decision structure for COBOL programs was a great help, especially when keeping in mind that in these days COBOL statements were terminated by a single point and complex decisions could easily run over 24 lines of code. It also showed that effective programming needed more. A major step was not in the use of tools but in the way, programs were structured. In an environment dominated by card readers, tapes and report writers (hard disks were expensive and had only limited capacity), each program depended on the structure of the input and output data. The fact that each programmer used his or her personal style and creativity did not make the maintenance of these programs easy. Some kind of craftmanship and best practices was needed. This led to a number of Structured Programming initiatives. The most widely used was Jackson Structured Programming (JSP)3 that Michael Jackson published in 1975.
At the same time Dr. Thurner launched a generator system that, based on the principles of structured programming, was able to produce much of the needed code. It used an abstract description of the structure of the data, in a language specifically defined for that task. The product was called DELTA4. It solved the problem that Dijkstra addressed in 1968. The programmer did not need to program and maintain any GO TO statement, only the generator produced them for the executable program5.
Over the years, Delta (later called Delta/ADS) was extended with a number of standard generators for standard functionality in Business Programming. PSD (Program Schema Description) and GRU (Control Break Processing) helped programmers to keep an overview of their programs and to focus on the unique functionality they have to implement while not being bothered by mechanisms needed to implement it.
Platform independence - Thanks to Generators
A major step in the development of Delta ADS was the concept of platform independence by the use of generators and macros. Back in the old days, each mainframe (compiler) had its own deviations of the COBOL standard. A program written for platform A was thus not usable on platform B without changing the source code. Not a big deal if you develop your software inhouse for your own use but it is for a software supplier that wants to install his software on many platforms. The use of the generators and macros in Delta ADS to deal with the platform specific aspects of the implementation meant that a program for many different target platforms could be maintained in one single source code object.
Platform independence did not only benefit software suppliers but after some time many Delta ADS users discovered that this possibility also facilitated a platform migration. The fact that an existing application could be migrated easily to a new platform when using Delta ADS is an important reason why many installations are still actively used, some for over 40 years, and that Delta/ADS is still alive and kicking after 50 years.
“I am pleased that after 50 years, Delta ADS is still being used successfully
for the development and migration of large and complex applications.”
Dr. Reinhold Thurner
The Future - and beyond
Like Delta DETAB, Delta ADS for COBOL and PL/I remains a part of our product portfolio. Over the years an estimated 2+ billion unique lines of code have been generated with our generator system, a number that is still growing each year. Initially, DETAB and Delta ADS were only available for the platforms for which they generated code.
Today they are also integrated into modern development environments such as Eclipse or Visual Studio and can generate cross-platform.
As the advantages of this generative approach to software development is still valued by our customers we remain committed to supporting them with our tools. The current release 6 of Delta ADS will certainly not be the last as we will continue to find solutions for the challenges our customers experience in their software development process.
50 Years of Delta ADS: Supporting the Developer
This year, 2026, we celebrate 50 years of Delta ADS. In our first retrospective we focussed on the techniques that played a big role in the area of code produce. Now we will look into another important part of Delta ADS, besides producing code: supporting the developer with tooling, prototyping, documentation and testing.
The first domain that Delta ADS took care of is the production of documentation. During the generation process, a number of different sorts of documents can be produced. Depending on the Delta ADS processors used, e.g. a program flow chart is created, an overview of all available locations and their usage becomes available and, last but not least, SPP has the option of generation a Nassi-Shneiderman diagram of a SPP-routine.
All these features enabled the developer to check the actual program against the design he made. But being able to communicate with the end-user about the results of a program has always been an important but difficult issue. Results could only be shown after running the program which needed a functional program and available data. Adapting afterwards was a tedious and error prone process. Therefore, Delta ADS allows for prototyping of reports and screens which produce the simulated results during the program generation. This gives the feedback at a much earlier stage, reducing the effort to correct the implementation.
Correcting existing programs has always been an important, time consuming but undervalued part of a programmer’s job.
Delta’s founding father Dr. Reinhold Thurner already found out in an early stage that: ‘for the correction of an error, 20% of the effort is needed to determine that there is an error and to pass the issue to the correct people. Next, in terms of time consuming, is to find the component that causes the error. The effort needed to fix the error is very often limited (but as we are in a hurry we tend to introduce new errors)’.
In a time where interactive debuggers were not available, finding an error was often a case of inserting display statements in the code to see where the program was when the error occurred. After fixing the flaw, these display statements had to be removed again. When another error came up, this process had to be repeated again.
Using a generator for the code produce opened up a solution for this time-consuming process. By activating one of the TEST-options (for the complete program or just one SPP-routine), the program will protocol each passed SPP-construct. This gives the programmer the much-needed insight in what a program did at runtime (and much faster compared to debugging) without having to program display-statements for that.
Additionally it can also produce statistics showing what logic was executed during the test run, giving an idea about the validity of the test and about general test coverage.
From the start, Delta ADS aimed at supporting the programmer to produce structured, well documented and maintainable code. A mission that we, after 50 years, remain to continue.
History
Article from Computerwoche, January 10, 1975 - Delta Author Dr. Reinhold Thurner:
"Multifunktionales Generator-System für moderne Software-Technologie: Ein Superding für die Avantgarde"
Download Language: Englisch - Version: MT21094.01
Life starts at 40 something: Delta ADS turns 50 this year
Developing software is looking to the future, but sometimes it is good to turn around and look back. As we did, we discovered that the foundations of our products were made almost half a century ago.
Read moreSources
1 Thurner R., "Entscheidungs-Tabellen: Aufbau-Anwendung-Programmierung", VDI- Taschenbuch T33, VDI Verlag, Duesseldorf, 1971.
2 Jeweils 100mal installiert:: Vorelle und Detab/GT | Computerwoche, 02.07.1976
3 Jackson, MA (1975), Principles of Program Design, Academic.
4 Multifunktionales Generator-System für moderne Software-Technologie: Ein Superding für die Avantgarde | Computerwoche, 10.10.1975
5 Dijkstra, Edsger W. (March 1968). "Letters to the editor: Go to statement considered harmful" (PDF). Communications of the ACM. 11 (3): 147–148. doi:10.1145/362929.362947. ISSN 0001-0782. S2CID 17469809.
p. 147, "The unbridled use of the go to statement has as an immediate consequence that it becomes terribly hard to find a meaningful set of coordinates in which to describe the process progress. ... The go to statement as it stands is just too primitive, it is too much an invitation to make a mess of one's program."
