The structure of the design automation language is examined and the sections of a system specification which can be translated independently of one another are identified.The ability to do incremental translation of changes in a system specification is demonstrated.The tables required for translator operation are defined and an algorithm for generating the required tables from a design language system specification is presented.The procedure for minimization of the system specification prior to logic circuit realization and a method for realization of the various sections of the system specification are described.

In this thesis, a survey on computer applications for teaching program ming and some graphical programming tools together with their underlying environments has been carried out and a graphical Pascal teaching tool is designed and implemented.

With the increasing complexity of digital systems, a new approach to system decomposition and modelling must be developed.

In interconnected networks, the performance of a network is affected heavily by the traffic transmitted from other networks. A network may become subject to congestion when the internetwork traffic increases rapidly. It is well known that congestion gives rise to a degradation in network performance. In this paper, we evaluate window-based congestion control mechanism in an internetwork environment. We also propose and study two dynamic window congestion control algorithms. These algorithms provide further control to window mechanism by adjusting the window size in accordance with the availability of the network resources at the destination. Dynamic algorithms are evaluated as compared with fixed window control by means of computer simulation. NW:Netvork GN:G.leWayFigure 1: Internetwork structure .IntroductionThe objective of congestion control in a computer network is to prevent or minimize the degradation in the system performance caused by the overload of messages. Various congestion control strategies have been proposed and implemented [5], [7]. Window mechanism is one of the effective congestion control schemes.The window mechanism limits the number of packets injected into the network by a source. The maximum number of packets allowed to be in transit gives the 'window size' between a source and destination. The packets in transit are the ones that have been transmitted, but not yet acknowledged by the destination [7].In this paper, a window based congestion control mechanism is evaluated in an interconnected network ('internetwork' for short) environment. With the window mechanism, each network is allowed to send up to a certain number of messages to another network without getting acknowledgement. The control is intended for the purpose of preventing congestion in gateways and attached networks caused by the overload of internetwork messages. First, an evaluation of fixed window control mechanism is provided. Then two dynamic window congestion control algorithms are proposed and studied. The algorithms provide further control to window mechanism by adjusting the window size in accordance with the availability of network resources at the destination.A comparison of dynamic algorithms with fixed window control is provided in terms of throughput and delay performance. It is shown that dynamic algorithms have considerable performance advantages over the fixed window control. Fig.1 presents the internetwork structure we study on where the individual local networks are connected to the system via their gateways. Simulation Model

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