【正文】 Systems Analysis and Design Working under control of a stored program, a puter processes data into information. Think about that definition for a minute. Any given puter application involves at least three ponents: hardware, software, and data. Merely writing a program isn39。t enough。 because the program is but one ponent in a system.A system is a group of ponents that work together to acplish an objective. For example, consider a payroll system. Its objective is paying employees. What ponents are involved? Each day，employees record their hours worked on time cards. At the end of each week, the time cards are collected and delivered to the puter center, where they are read into a payroll program. As it runs, the program accesses data files. Finally, the paychecks are printed and distributed. For the system to work, people, procedures, input and output media, files, hardware, and software must be carefully coordinated. Note that the program is but one ponent in a system.Computerbased systems are developed because people need information. Those people, called users, generally know what is required, but may lack the expertise to obtain it. Technical professionals, such as programmers, have the expertise, but may lack training in the user39。s field. To plicate matters, users and programmers often seem to speak different languages, leading to munication problems. A systems analyst is a professional who translates user needs into technical terms, thus serving as a bridge between users and technical professionals.Like an engineer or an architect, a systems analyst solves problems by bining solid technical skills with insight, imagination, and a touch of art. Generally, the analyst follows a welldefined, methodical process that includes at least the following steps。1. Problem definition2. Analysis3. Design4. Implementation 5. MaintenanceAt the end of each step, results are documented and shared with both the user and the programmers. The idea is to catch and correct errors and misunderstandings as early as possible. Perhaps the best way to illustrate the process is through example.Picture a small clothing store that purchases merchandise at wholesale, displays this stock, and sells it to customers at retail. On the one hand, too much stock represents an unnecessary expense. On the other hand, a poor selection discourages shoppers. Ideally, a balance can be achieved: enough, but not too much.Complicating matters is the fact that inventory is constantly changing, with customer purchases depleting stock, and returns and reorders adding to it. [1] The owner would like to track inventory levels and reorder and given item just before the store runs out. For a single item, the task is easyjust count the stockonhand. Unfortunately, the store has hundreds of different items, and keeping track of each one is impractical. Perhaps a puter might help.21 Problem DefinitionThe first step in the systems analysis and design process is problem definition. The analyst39。s objective is determining what the user (in this case, the store39。s owner) needs. Note that, as the process begins, the user possesses the critical information, and the analyst must listen and learn. Few users are technical experts. Most see the puter as a magic box, and are not concerned with how it works. At this stage, the analyst has no business even thinking about programs, files, and puter hardware, but must municate with the user on his or her own term.The idea is to ensure that both the user and the analyst are thinking about the same thingThus, a clear, written statement expressing the analyst39。s understanding of the problem is essential. The user should review and correct this written statement. The time to catch misunderstandings and oversights is now, before time, money and effort are wasted.Often, following a preliminary problem definition, the analyst performs a feasibility study. The study a brief capsule version of the entire systems analysis and design process, attempts to answer three questions:1. Can the problem be solved?2. Can it be salved in the user39。s environment?3. Can it be solved at a reasonable cost?If the answer to any one of these questions is no, the system should