Abstract Janus is a symbolic language used to embody the information which is normally passed from the analysis phase of a compiler to the code generators. It is designed for transporting software: A program coded in a high level language can be translated to Janus on one computer, and the resulting output translated to assembly code on another. (The STAGE2 macro processor could be used for the second translation.) In this paper we present the principles upon which Janus is based, and show that it is suited to a wide range of source languages and target computers.

This paper describes the development of a version of the MITEM text editor in which heavily-used sections of code are obeyed directly while other sections are generated into a pseudo-core which is interpreted. The main ideas underlying this work are adaptable code generation, selective optimisation of run time and program space in code generation and the use of mixed code. A general mixed code system promises substantial advantages for debugging and program monitoring.

Abstract This paper discusses the use of abstract machine modelling as a technique for producing portable software, i.e. software which can be moved readily from one computer to another. An overview of the principles involved is presented and a critical examination made of three existing abstract machines which were used respectively to implement a macro processor, a text editor and a BASIC compiler.

Abstract COTAN is a multi‐acess system designed to operate on linked KDF9–PDP8 computers. It supports 20 remote teletypes and provides the online user with both remote job entry and interactive capabilities The development of COTAN relied heavily on the continuing availability of online access from an early stage in the project. Access was first obtained through the monitor console on the KDF9 and this was then used to ‘bootstrap’ the implementation of the multi‐access facilities. The new software was checked out in a real time, online test bed called an ‘environmental simulator’. This provided a close approximation to the ultimate operating conditions and enabled the system to be brought to a high degree of reliability before being placed in service.

The techniques of abstract machine modelling and macro processing can be used to construct software which is easily moved from one computer to another. This paper describes a system developed at the University of Colorado which has been implemented on 8 different machines, with efforts ranging from 1 man-day to 1 man-week. We feel that these techniques offer a possible solution to the "software crisis" which is plaguing the computer industry today.

This paper describes the first stage of a project to provide multi-access facilities in the Egdon system operating on a KDF9. Initially, on-line access was obtained through the single monitor console and a user could interrupt a background job to initiate such foreground tasks as program amendment and execution.