information systems course

Nassi-Shneiderman charts 56.1 Purpose Nassi-Shneiderman charts were developed by Nassi and Shneiderman as an alternative to traditional logic flowcharts. Their intent was to provide a structured, hierarchical, graphical view of the flow of logic through a program, a routine, a module, or a process. Nassi-Shneiderman charts are used to document, plan, and design detailed program logic. 56.2 Strengths, weaknesses, and limitations A properly prepared Nassi-Shneiderman chart can illustrate the flow of logic through a module or routine at a glance. Nassi-Shneiderman charts are useful for describing or planning relatively small modules, routines, or processes. They can be used to clearly show nesting and recursion, and are easily converted to structured code. Nassi-Shneiderman charts should not be used for documenting complete programs or large routines. As a general rule, Nassi-Shneiderman charts should be limited to a single page with no more than 20 subdivisions. For larger rout...

Logic (process) flowcharts 55.1 Purpose A logic or process flowchart is a graphical representation of the flow of logic, control, data, or paperwork through a program, a routine, a module, or a process. The flowchart specifies or documents the order in which tasks are performed. Flowcharts are used for documentation and for planning. 55.2 Strengths, weaknesses, and limitations A properly prepared flowchart can illustrate logical flow at a glance. Flowcharts are useful for describing or planning the logical flow through a relatively small module, routine, or process. A flowchart is a good choice for describing or planning a decision-based algorithm where the number of alternative paths does not exceed three. Logic flowcharts should not be used for documenting complete programs or large routines. Flowcharts extending over multiple pages are difficult to follow, and flowcharts (of any size) are difficult to maintain. If a flowchart spills beyond a single page (or a single screen...

Cable Fault Locating Methods This section describes the existing methods and techniques used for fault location. Faults may vary widely, and similar faults may exhibit different symptoms depending upon the cable type, operating voltage, soil condition, and so on. Basically, faults can be considered to be shorts, opens, or nonlinear. A short is defined as a fault when the conductor is shorted to the ground, neutral, or another phase with a low impedance path. This type of fault is also referred to as a shunt fault. An open fault is defined as when the conductor is physically broken and no current flows at or beyond the point of break. The nonlinear type of fault exhibits the characteristics of an unfaulted conductor at low voltages but shows a short at operating or higher voltages. This nonlinear fault is also known as a high-resistance fault. These fault types are shown in Figure 6.8. Fault location methods can be divided into two general categories: terminal techniques and tracing...

Structured program design 62.1 Purpose This chapter discusses the basic principles that underlie structured program design and functional decomposition. The objective of functional decomposition is to design structured programs that are easy to test, debug, and maintain. The basic idea is to break down (or decompose) a program into logically independent modules based on the processes or tasks they perform. 62.2 Strengths, weaknesses, and limitations Because the detailed computational logic is grouped into independent, single function modules, well-structured programs are easier to test, debug, and maintain than are unstructured programs. Independent modules can be independently coded and tested. The control structure allows the entire program to be tested top down, one module at a time. When an error occurs, it is often possible to quickly isolate the likely cause to a single module. During the maintenance phase, independent modules can be replaced or modified with minimal ripp...