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فریاد Faryad

Hardware and software
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In order to use computers effectively to solve problems in our environment, computer systems are devised. A ‘system‘ implies a good mixture of integrated parts working together to form a useful whole. Computer systems may be discussed in two parts.

 The first part is hardware - the physical, electronic, and electromechanical devices that are thought of and recognized as ‘computers’. The second part is software - the programs that control and coordinate the activities of the computer hardware and that direct the processing of data.
 Figure 5.1 shows diagrammatically the basic components of computer 10 hardware joined together in a computer system. The centerpiece is called either the computer, the processor, or usually the central processing unit (CPU). The term ‘computer‘ usually refers to those parts of the hardware in which calculations and other data manipulations are performed, and to the internal memory in which data and instructions are stored during the actual execution of programs. The various peripherals, which include input and/or output devices, various secondary memory devices, and so on, are attached to the CPU.
 Computer software can be divided into two very broad categories systems software and applications software. The former is often simply referred to as ‘systems’. These, when brought into internal memory, direct the computer to perform tasks. The latter may be provided along with the hardware by a systems supplier as part of a computer product designed to answer a specific need in certain areas. These complete hardware/software products are called turnkey systems.
 The success or failure of any computer system depends on the skill with which the hardware and software components are selected and blended. A poorly chosen system can be a monstrosity incapable of performing the tasks for which it was originally acquired.

 


Computer capabilities and limitations
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Like all machines, a computer needs to be directed and controlled in order to perform a task successfully. Until such time as a program is prepared and stored in the computer’s memory, the computer ’knows’ absolutely nothing, not even how to accept or reject data. Even the most sophisticated computer, no matter how capable it is, must be told what to do. Until the capabilities and the limitations of a computer are recognized, its usefulness cannot be thoroughly understood.

 In the first place, it should be recognized that computers are capable of doing repetitive operations. A computer can perform similar operations thousands of times, without becoming bored, tired, or even careless. Secondly, computers can process information at extremely rapid rates. For example, modern computers can solve certain classes of arithmetic problems millions of times faster than a skilled mathematician. Speeds for performing decision-making operations are comparable to those for arithmetic operations but input-output operations, however, involve mechanical motion and hence require more time. On a typical computer system, cards are read at an average speed of 1000 cards per minute and as many as 1000 lines can be printed at the same rate.
 Thirdly, computers may be programmed to calculate answers to whatever level of accuracy is specified by the programmer. In spite of newspaper headlines such as ‘Computer Fails’, these machines are very accurate and reliable especially when the number of operations they can perform every second is considered. Because they are man-made machines, they sometimes malfunction or break down and have to be repaired. However, in most instances when the computer fails, it is due to human error and is not the fault of the computer at all.
 In the fourth place, general-purpose computers can be programmed to solve various types of problems because of their flexibility. One of the most important reasons why computers are so widely used today is that almost every big problem can be solved by solving a number of little problems one after another. Finally, a computer, unlike a human being, has no intuition. A person may suddenly find the answer to a problem without working out too many of the details, but a computer can only proceed as it has been programmed to.
 Using the very limited capabilities possessed by all computers, the task of producing a university payroll, for instance, can be done quite easily. The following kinds of things need be done for each employee on the payroll. First: Input information about the employee such as wage rate, hours worked, tax rate, unemployment insurance, and pension deductions. Second: Do some simple arithmetic and decision making operations. Third: Output a few printed lines on a cheque. By repeating this process over and over again, the payroll will eventually be completed.