https://ir.unisa.ac.za/handle/10500/23969 Wed, 06 May 2026 12:45:04 GMT 2026-05-06T12:45:04Z https://ir.unisa.ac.za/handle/10500/23976 A Hardware-Based Real-Time Operating System Rodd, M. G. The efficient use of multiprogrammed industrial control computers is largely a function of the relationship between hardware and software. A shift in this relationship is desirable, since multiprogrammed computers typically spend a large proportion of computing time in handling their own organization. This situation is compounded in many time-critical industrial process-control applications. This paper proposes that a possible solution lies in the adoption of a hardware-based real-time operating system. The system consists of a microcontroller working in close relationship with a conventional minicomputer. To retain a high degree offlexibility, the microcontroller makes use ofmicroprograrnmable, bipolar, bit-slice microprocessor elements. In essense, the unit executes the principal functions of a real-time operating system, acts as a pre-processor for all incoming requests, and ensures a high rate of task switching. The system has been applied in a series of real-time experimental configurations. These were controlled successively by the conventional, software- implemented approach, and by the proposed system. The respective performances were evaluated. The new strategy is shown to result in a better and more economical industrial controller. Mon, 01 Jan 1979 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/23976 1979-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/23975 Text Compression Techniques Radue, J. E. The benefits associated with text compression include more efficient use of peripheral devices. faster information transfer rates and, in some cases, improved sorting speeds through the use of shorter sort keys. However. these advantages must be balanced against a slight increase in CPU-time and the extra storage required for the associated code tables. Information theory and statistics of English provide a background for the discussion of various text compression algorithms. The common objective of the methods described is to reduce the physical size of the text file while maintaining a complete representation of the information (reversible compression). The methods can be divided into two main classes: ( a) those that re-define the symbol codes to more accurate reflect the information content of each symbol, and (b) those that use special codes to represent commonly occurring groups of symbols, thereby reducing redundancy due to mutual information between symbols. Compression techniques not covered include those dealing with data files and with telemetry. Finally. another approach to compression is described. which also holds some promise for automatic indexing and simpler inverted file design in document retrieval systems. Mon, 01 Jan 1979 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/23975 1979-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/23974 The P-NP Question and Recent Independence Results Philips, N.C.K. Despite intensive research the P = NP question is unresolved and the research suggests thatitis hard to answer. The corresponding question for query machines with recursive oracles is undecidable in set theory. Simply determining whether a procedure halts or the running time of an algorithm may be harder than we expect. There is a Turing machine which does not halt yet its halting is undecidable in set theory. There is an algorithm which runs in time n2 yet it cannot be proved in set theory to run in any time less than 2". 26 Mon, 01 Jan 1979 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/23974 1979-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/23973 Distributed Computer Systems - A Review Peberdy, N.J. The past five years have seen a dramatic changeabout in traditional hardware/software relationships: hardware costs have plummeted, and the size, environmental requirements and reliability of computing elements have altered drastically. It now becomes feasible to distribute a computing system, such that processors may be placed adjacent to the processes they control. These distributed computing modules operate in an essentially parallel mode, but are required to communicate in order to co-ordinate their activities. Reliable, secure communication systems must be established to ensure correct operation. Such systems are not only functions of the electrical hardware employed, but also of the software support provided. Of vital importance are the protocols selected, which define and detail an agreed procedure for the exchange of information. This paper reviews the fundamental software considerations in the design of computer networks, with specific relevance for process-control applications. It discusses in detail, inter-connection strategies and protocols and briefly examines currently adopted schemes. The implications offully decentralized system control are considered. Of particular concern is the question of the production of reliable, fault-tolerant, secure systems. Mon, 01 Jan 1979 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/23973 1979-01-01T00:00:00Z