STAC(ID:2531/sta002)Symbolic macroprocessor for DEUCEfor Storage Allocation and Coding Program R.A.E. Farnborough Symbolic macro-assembler for the English Electric DEUCE. Places Related languages
References: INTRODUCTION Despite the organization of vast libraries of subroutines and programs, and the facilities for testing new programs, a real need has grown up for flexible and powerful schemes, capable of being used to construct new DEUCE programs in a fraction of the normal time. During the last four years a variety of such schemes has grown up for DEUCE, and the present paper and a companion paper by Mr. S. J. M. Denison, reviews some of these, and fits them into perspective. The schemes STAC, G.I.P. (General Interpretive Program), T.I.P. (Tabular Interpretive Program), Alphacode, GEORGE, SODA, Easicode, STEVE and the Alphacode Tabulator have been produced at intervals at various DEUCE establishments, to all of which credit should be given for the introduction of new ideas and exploitation of older ones. A study of the way in which most of these schemes develop ideas in the others, and contribute new techniques in itself an interesting genealogical exercise. Extract: STAC STAC One of the earlier programming aids was a scheme (from R.A.E. Farnborough) in which the flow diagram having been prepared, and the storage allocated, DEUCE itself was made to allocate Wait and Timing numbers and so allow a by-pass from steps 5 to step 9 on Fig. 1. More recently this has been superseded by STAC (Storage Allocation and Coding) which effectively mechanizes those steps between 4 and 9. The separation of a program here ends with a flow diagram specifying merely the source, destination and length of transfer. The STAC program will then take these instructions, and given the storage place available will make a satisfactory job of allocating the storage and optimum coding the program. In doing so it will insert any subroutines called for, and plant and obey their links. If the inner loops of programs are so marked, it will give them priority in the coding, and as an additional aid to the programmer it will accept symbolic addresses for any stores and allocate suitable minor cycles in delay lines for them. Not all the instructions need be specified in the flow diagram in DEUCE order code, for STAC can accept a few so called 'super instructions' which it then breaks down into the correct sequence of machine-instructions. The output of STAC is a fully-coded program pack, a full decimal copy of the flow diagram, a list of the real addresses allocated to the symbolic addresses, and a statement of which storage space remains unused in case the program should require further modification. The scheme is of greatest use to the non-professional programmer who is not as a rule impressed by efforts to cut off milliseconds from a program, if they result in the completed program being delayed! in Goodman, Richard (ed) "Annual Review in Automatic Programming "(1) 1960 Pergamon Press, Oxford view details Most of the papers are written in a style and manner which seem to have become universally accepted for papers on computer programming, at least in the English-speaking world and probably in others. This style insists on a liberal dosage of impressively detailed flow charts which, considering the well-known and understandable reluctance of programmers to read their own programs much less those of others, one suspects most readers hastily skip over, willingly granting their authenticity. The flow charts are invariably accompanied by long lists of special instructions described in the private patois of the author, who seems blissfully unaware or unconcerned that his specially constructed vocabulary of acronyms may present;. rough going to the reader from the inlying provinces. Finally, the style demands long and wearisome descriptions of basic concepts (e.g., subroutine; symbolic instruction, etc.) long since familiar to the average reader, some indication of difficulties as yet to be surmounted (e.g., automatic storage allocation; easier debugging; et al). Nevertheless, the volume does give some idea of the status of automatic programming systems in Great Britain in early 1959. It also contains a concise description of the 709 SHARE operating system, and another brief account of FLOW-MATIC and MATH-MATIC. There are two interesting appendices worthy of mention. Appendix One consists of reprints of two papers by the late A. M. Turing, "On Computable Numbers with an Application to the Entscheidungsproblem", in which the "Turing machine" was conceived, and a brief corrective note on the same subject. Appendix Two contains the "Preliminary Report of ~ ACM-GAMM Committee on an International Algebraic Language", since published elsewhere. The reviewer cannot suppress the question of whether this sort of material (Appendices excepted), so soon obsolescent or obsolete and so difficult to present adequately in short papers, deserves the effort and expense required to reproduce it between the bound hard covers of a handsome book. in ACM Computing Reviews 2(03) May-June 1961 view details DEUCE The English Electric DEUCE grew out of an active collaboration between English Electric and NPL. The DEUCE was based closely on the Pilot ACE (Haley i956). The initial software effort for the DEUCE lay in converting the existing Pilot ACE programs developed by NPL. Most of this work was done during 1955 in a combined effort between the users of the first three DEUCES, which were installed at English Electric, NPL, and the Royal Aircraft Establishment. This conversion work was in fact coordinated by NPL; it seems that in the mid-1950s English Electric did not see the provision of programming systems as part of their brief, although they did organize the DEUCE Users Group and a library service. Several active programming groups were associated with DEUCE installations, and by 1958 three important interpretive schemes for the DEUCE had emerged: GIP, TIP, and Alphacode (Robinson 1959). These three schemes had complementary domains of application: GIP was, of course, the famous matrix interpretive scheme from NPL, TIP was used for calculations on vectors, and Alphacode was used for scalars. The GIP matrix scheme was easily the most important programming system for DEUCE. Apart from its remarkably high speed, CIP was noted for its reliability. By means of check sums and other devices, complete confidence could be had in the results in spite of the inherent unreliability of the DEUCE (which had no parity checking, for example). The TIP (Tabular Interpretive Program) scheme was in effect a variant of GIP restricted to vector operations. The system was designed by the DEUCE group at Bristol Aero Engines to simplify programming for engineers and was widely used. TIP was a rather elegant system and required no formal understanding of linear algebra. It was intended to be accessible to anyone who was familiar with a "desk machine ... and a sheet of paper ruled into rows and columns" (Robinson 1959). TIP is an interesting relic of the transition from machine language to true programming languages. The third interpretive scheme, Alphacode, was specified by S. J. M. Denison of English Electric as an automatic coding system for naive users and for one-time jobs; Alphacode was directly inspired by the Manchester Mark I Autocode (Denison 1959). The interpreter produced programs that were typically about five times slower than conventionally coded programs, actually a considerable achievement considering the high speed of DEUCE when optimally coded. In November 1957 a project for an Alphacode translator (as opposed to the existing interpreter) was begun (Duncan and Huxtable 1961). The aim was the exceedingly ambitious one of producing translated programs as good as hand-coded ones. The translator was developed by F. G. Duncan, working at first with E. N. Hawkins and later with D. R. Huxtable. The system came into use toward the end of 1959. It was one of the most impressive programming achievements of its day, both in terms of sheer size (22,000 instructions) and in the difficulty of producing code for a machine with a multilevel store. The translator in practice produced code that was about two-thirds as good as handwritten code, a truly remarkable achievement given the complexity and subtlety of programming for the DEUCE. Several other programming schemes were produced for the DEUCE by other installations in the late 1950s. These included STAC, STEVE, GEORGE, SODA, and EASICODE (Robinson 1959). AH these systems were made available through the Users Group, but they do not appear to have been used as widely as the schemes already described. The development of software for DEUCE can be summarized as follows. The existence of a large amount of high-quality software from NPL led English Electric into believing that it was unnecessary to develop further programming systems. English Electric did see the need to coordinate and distribute programs through the Users Group and to organize programming courses. English Electric's failure to make a timely provision of an autorpatic programming system for DEUCE led to a number of ad hoc developments at various DEUCE installations during the period 1957-1959, which was a wasteful duplication of effort. In underwriting the Alphacode translator, however, English Electric demonstrated that it had at last come to recognize its duty to provide programming systems for the DEUCE. In January 1960 English Electric transferred its programming staff to the Data Processing and Control Systems Division at Kidsgrove, where an automatic programming section was established under the management of F. G. Duncan (1979). At this point, machines such as the KDF 9, for which excellent software was produced, were on the horizon. Extract: Conclusions Conclusions When we compare the development of programming at the three centers -- Cambridge, Manchester, and Teddington -- there are several factors to consider. First, we must consider the quality of the programming system; this is a subjective issue that ranges from the purely aesthetic to the severely practical -- for example, from the elegance of an implementation at one extreme to the speed of a matrix inversion at the other. We must also consider the failures of the three centers, especially the failure to devise a programming system that exploited the full potential of the hardware. Finally, we must consider the influence of the programming systems on other groups; this is less subjective -- it was described in the previous two sections and is summarized in Figure 2. Few could argue that Cambridge devised the best of the early programming systems. The work done by Wilkes and Wheeler stood out as a model of programming excellence. Cambridge made several outstanding contributions to early programming: the use of closed subroutines and parameters, the systematic organization of a subroutine library, interpretive routines, and the development of debugging routines. Perhaps the finest innovation was the use of a symbolic notation for programming, as opposed to the use of octal or some variant. It is difficult for us today to appreciate the originality of this concept. If Cambridge can be said to have had a failure, it was the failure to develop programming languages and autocodes during the middle and late 1950s, as reflected in the second edition of Wilkes, Wheeler, and Gill (1957), of which Hamming said in a review, It is perhaps inevitable that the second edition, though thoroughly revised, does not represent an equally great step forward, but it is actually disappointing to find that they are no longer at the forefront of theoretical coding. (Hamming 1958)] By neglecting research into programming languages, Cambridge forfeited its preeminence in the programming field. In the early 1950s, however, Cambridge was by far the most important influence on programming in Britain. This came about partly through the excellence of the programming system and partly through the efforts that Cambridge made to promote its ideas. Two machines (I`EO and TREAC) based their programming system directly on EDSAC, and five machines (Nicholas, the Elliott 401 and 402, MOSAIC, and Pegasus) were strongly influenced by it. It is also probably true that no programming group was entirely uninfluenced by the Cambridge work. Overseas, the influence of the EDSAC programming system was just as great, largely through the classic programming textbook by Wilkes, Wheeler, and Gill (1951) (see Campbell-Kelly 1980a). At Manchester the programming system devised by Turing for the Mark I makes a disappointing contrast with the elegance of the Cambridge work. From the point of view of notation, it is difficult to find a single redeeming feature. Probably the only feature of real merit was the concept of dividing a program into physical and logical pages. Echoes of this idea can be discerned in today's segmented computers. In its way, Turing's programming system did have considerable influence, for all efforts to replace it with something more suitable were curiously unsuccessful. Thus programmers for both Mark Is and all seven Mark Iota's had to struggle with Turing's clumsy teleprinter notation throughout the life of these machines. Here is perhaps one of the most valuable lessons of this study: poor design decisions taken early on are almost impossible to correct later. Thus even when people with a Cambridge background arrived at Manchester, they were unable to make a really fresh start. By producing two successive input routines that were not much better than Turing's, they managed to combine the worst of both worlds: an unsatisfactory programming system that was not even a stable one. The one real high spot of the Manchester programming activity was Brooker's Mark I Autocode. Brooker's achievement was the most important programming event of the mid-1950s in Britain. If Brooker had not devised his autocode at that time, programming in Britain might have developed very differently. The autocodes for DEUCE and Pegasus were directly inspired by Brooker's and had considerable notational similarities with it. Beyond the time scale of this paper, Brooker's Mark I Autocode and his later Mercury Autocode (1958) were a dominant influence on British programming until well into the 1960s, when languages such as ALGOL 60 and FORTRAN came onto the scene in Britain. Of the three programming systems devised at Cambridge, Manchester, and Teddington, it is probably the latter that inspires the least passion. Ii the punching of programs in pure binary was an efficient method, it was also a singularly uninspiring one. Curiously, aficionados of the Pilot ACE and the DEUCE had great enthusiasm for programming these machines, which really had more to do with the joys of optimum coding and exploiting the eccentric architecture than with any merits of the programming system. In many ways the crudity of the programming system for the Pilot ACE was understandable: the speed of events, the lack of a backing store, and so on. But perpetuating it on the DEUCE was a minor tragedy; by replicating the programming system on the 32 commercially manufactured DEUCES, literally hundreds of rank-and-file programmers were imbued in this poor style of programming. MOSAIC (Section 3.4) shows that it was entirely possible to devise a satisfactory programming system for machines of the ACE pattern; it is most unfortunate that this work was not well enough known to influence events. NPL did, however, have one notable programming-success: the GIP matrix scheme devised by Woodger and Munday. This scheme became the sole reason for the existence of many DEUCES. The reliability of the mathematical programs produced by NPL, their comprehensiveness, and their speed have become almost legendary. A history of numerical methods in Britain would no doubt reveal the true role of NPL in establishing the methods of linear algebra as an analytical tool for the engineer. In an interview, P. M. Woodward, one of the principals of the TREAC programming activity, recalled, "Our impression was that Cambridge mattered in software whereas Manchester mattered in hardware" (Woodward and Jenkins 1977). He might well have added that NPL mattered in numerical methods. Because this paper has been primarily concerned with the development of programming during the period 1945-1955, Cambridge has received pride of place as the leading innovator. Had the paper been concerned principally with hardware or numerical methods, however, the ranking of the three centers would have been different. But considered purely as innovators of programming, there can be no question that Cambridge stood well above the rest. Abstract: By 1950 there were three influential centers of programming in Britain where working computers had been constructed: Cambridge University (the EDSAC), Manchester University (the Mark I), and the National Physical Laboratory (the Pilot ACE). At each of these centers a distinctive style of programming evolved, largely independently of the others. This paper describes how the three schools of programming influenced programming for the other stored-program computers constructed in Britain up to the year 1955. These machines included several prototype and research computers, as well as five commercially manufactured machines. The paper concludes with a comparative assessment of the three schools of programming. in Annals of the History of Computing 4(2) April 1982 IEEE view details |