- Apr 01, 2018
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What is System Design?
A new system must be designed based on the user requirements and the detailed analysis of the new systems. This is the system design phase. This is the most important phase in the development of a new system. It focuses on delivering the requirements as specified in the feasibility report. The main objectives of the design are security, flexibility, efficiency, cost and practicability.
The systems design is in two stages. The preliminary or general design stage and structure or detailed design stage.
The features of a new system are specified in the preliminary design. The cost of implementing these features and the benefits to be derived are also estimated. The development team can follow up on the detailed design stage if the project is still feasible.
The structure or detailed design specifies the stage where computer oriented work begins in earnest. The design of the system becomes more structural at this stage. Structure design is a blue print of a computer system components and inter-relationship among the same components as the original problem. The input, output and processing specifications are drawn up in detail. The programming language and the platform in which the new system will run are also decided at this stage.
The tools and techniques used for designing include flowchart, dataflow diagrams, data dictionary, structure English, decision table and the decision tree.
Output design refers to designing computer screens on which output data will be shown. It also describes the paper-based reports that a system will generate. The three kinds of a system output include external output, internal output and internal system output.
In the external output, results will be sent out to people outside the user’s organization. These outputs include purchase orders and invoices.
In the internal output, results will be distributed within the organization. These include management reports, error reports and audit trails.
The internal system output refers to information relating to the operations of the system itself. This includes system operating statistics and reports.
Things to consider in output designing are content and format of output, frequency of production, triggers or event that will produce the output, volume of expected output, output medium, output controls & costs and benefits of the output.
Input design refers to specifying the information which is needed by the system and converting this human sensible form to computer form. Input design is closely bound up with data collection and data capture.
Things to consider in input designing are categorization of master data and the transaction volumes of input, frequency of input, sequence of input, data collection / capture points, input medium, data validation checks what should be input & in which format and input controls.
DOCUMENT DESIGN (FORM DESIGN)
Document design refers to designing paper document that will be used for the input and output of data from a system.
The analyst may have to design a large number of different forms or documents for the input data and output reports. A good form will allow the requirement to be obtained, transmitted, interpreted, filed and retrieved at minimum total cost.
Things to consider in document designing are identification of form titles & numbers, purpose of document, sequence of the data, volume of use, frequency of preparation and files affected by the input.
Code design refers to designing coding system for different items and records in a system. The purpose of the code is to identify items more concisely and precisely than written descriptions. Codes can save data capture and preparation time. A good coding system saves internal storage space in a computer system.
Various coding systems that may be used in code designing include sequence codes, block codes, significant, digit codes, hierarchical codes and faceted codes. Things to consider in code designing are easiness, scalability, flexibility, unique code for key items, level of comprehensiveness, brief to save clerical time and storage space, error correction should be easy, no duplication and codes should be issued form a single central point.
SCREEN / DIALOGUE DESIGN
Screen design refers to designing the systems screens or dialogue in such a way that the data can be input to the system through them. It also ensures that output can be displayed on them in the most efficient way.
Screen design considerations include user friendly GUI, online help, short court keys, standard layouts, precise but complete information and customizability.
File design refers to the designing of the file structure of a system in an organized form. The file holds all the necessary information needed to coordinate the activities of a system from input to output.
The different types of files include master, transaction, backup, archive, table, report, dump and library files.
The files are organized in sequential, random and indexed formats.
The major criteria for selecting a file organization include method of processing, size of data, file inquiry capability, file volatility, response time and activity ratio.
The output design, input design, document or form design, code design and screen design/dialogue design are detailed designs
These describe the features the system architect puts into consideration before designing the processes of the system.