Chapter 5: Appendix Input-Output Forecasting

Chapter 5: Appendix Input-Output Forecasting

Input-output forecasting is a method of forecasting that analyzes the interrelationships between different sectors of the economy to project future economic activity. It involves identifying the inputs required by each sector to produce its outputs and how these inputs, in turn, affect the production of other sectors. To perform any useful task, the microcomputer must interact with the outside world. The input-output (I/O) devices or peripherals provide the necessary data communications link between the microprocessor and its environment. Typically, information is accepted from the input devices, it is processed and the results of the data processing are then sent to one or more output devices. In a microcomputer system, the input-output operations are particularly important since, in the majority of applications, the microprocessor spends the greatest part of its time interacting with the I/O devices. The operation of the I/O devices is usually independent of that of the microprocessor, and a procedure must be adopted to synchronise program execution with their operation during data transmission. There are three basic types of input-output according to the method of controlling and synchronising data transfer: (i) Program-controlled I/O (ii) Interrupt-controlled I/O (iii) Direct-memory-access I/O. The type of input-output used in a particular application will depend on three main factors: (i) The rate at which data must be transmitted. (ii) The maximum time delay which can be accepted between the I/O device signalling its readiness to transmit or receive data and the data transfer actually taking place