Digital Electronics: Principles, Devices and Applications

15Computer FundamentalsThis chapter focuses mainly on computer hardware fundamentals, with a brief introduction to some ofthe relevant software-related topics. The chapter begins with a brief description of different types ofcomputer system, from giant supercomputers to tiny digital assistants, which is then followed up byanatomical description of a generalized computer system, with particular reference to microcomputersystems. Other hardware-related topics that are extensively covered include input/output devices andmemory devices.15.1 Anatomy of a ComputerThe basic functional blocks of a computer comprise the central processing unit (CPU), memory andinput and output ports. These functional blocks are depicted in the block schematic arrangement ofFig. 15.1. As is clear from the figure, these functional blocks are connected to each other by internalbuses. The CPU is the brain of the computer. It is basically a microprocessor with associated circuits.Ports are physical interfaces on the computer, through which the computer interacts with the inputand output devices. Memories are storage devices used for storing data and instructions. The CPUfetches the data and instructions by sending the address of the memory location on the address bus.The data and the instructions are then transferred to the CPU by the data bus. The CPU then executesthe instructions and stores the processed data in the memory or sends them to an output device via thedata bus. It may be mentioned here that in most cases the instructions modify the data stored in thememory or obtained from an input device.15.1.1 Central Processing UnitAs mentioned above, the CPU is the brain of the computer. The fundamental operation of the CPU isto execute a sequence of stored instructions called a program. In other words, it controls the executionDigital Electronics: Principles, Devices and Applications Anil K. Maini©2007 John Wiley &Sons, Ltd. ISBN: 978-0-470-03214-5