Basic Concepts of Systems

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BASIC CONCEPTS OF SYSTEMS

      Question   1

      Explain the concept of decomposition   with the help of an example. (Final May 2003)

      Answer

      A computer system is difficult to comprehend when considered as a whole. Therefore, it is better that the system is decomposed or factored into sub systems. The boundaries and interfaces are defined, so that sum of the sub systems constitutes the entire system. This process of decomposition is continued with sub systems divided into smaller sub systems until the smallest sub systems are of manageable size. The sub systems resulting from this process generally form hierarchical structure as shown in the figure given below:

                                System

          Subsystem A
Subsystem B
Subsystem C

          A1 A2 B1 B2
B3 C1 C2

A21
A22
C11
C12

Hierarchical relations of subsystems

An example of decomposition is the factoring of an information processing   system into sub systems. One approach to decomposition might proceed as follows:
1.Information system divided into sub system such as: Sales and order entry
          Inventory

          Production

          Personnel and payroll

          Purchasing

          Accounting and control

          Planning

          Environmental intelligence

      2. Each sub system is divided further into sub systems. For example, the personnel and payroll sub system might be divided into the following smaller sub systems:
          Creation and update of personnel pay roll records. Personnel reports
          Payroll data entry and validation Hourly payroll processing Salaried payroll processing Payroll reports for management Payroll reports for Government
      3. If   the   task   is   to   design   and program a new system,   the   sub systems   (major applications) defined above might be further sub divided into smaller sub systems or modules. For example, the hourly payroll processing sub system might be...