Charting Techniques
1. System outline charts : -
2. System flowcharts (National map).
3. Run flowcharts (State map).
4. Program flowcharts (District map).
1. System outline charts : -
These charts merely lists inputs, files, processes, and outputs required without considering any sequence.
For example, chart of sales order processing :
Srinivas MBA : MIS : CH 8 2009
163 2. System Flowchart :-
It presents an overview of the data flow through all parts of a data processing system.
It also represents flow of documents, the operations or the activities performed.
The system flowchart for a computer system consists of :
1. The sources from which input data is prepared and the devices used.
2. The processing steps or sequence of operations involved.
3. Intermediary or final output prepared and the device used for their storage or printing.
Example : PAYROLL
Payroll data -> Compute monthly compensation -> Pay cheques & payroll reports.
Srinivas MBA : MIS : CH 8 2009
164 3. Run Flowcharts :-
This is the detailed version of the system flowcharts. It contains the details of each compute operation.
Example : Sales order processing system :
Srinivas MBA : MIS : CH 8 2009
165
Srinivas MBA : MIS : CH 8 2009
166 Program Flowcharts :
Program flowcharts are the most detailed and are concerned with the logical / arithmetic operations on data within CPU.
Here, the data flows between CPU and input / output.
Start / end
Box
(Process)
Diamond (decision)
Input / Output Document
Srinivas MBA : MIS : CH 8 2009
167 Floppy diskette
Or online storage
Magnetic Tape
Manual Input
Display
Srinivas MBA : MIS : CH 8 2009
168
Srinivas MBA : MIS : CH 8 2009
169 Data Flow Diagrams :
Data Flow Diagram (DFD) is a graphical description of a system's data and the processes that transform these data from one 'form to another. Some graphical symbols are used to construct data flow diagram.
These symbols are given below.
A DFD may consist of several external entities, processes, and data flows and data stores. An arrow identifies data flow -data in motion. These data flows
Srinivas MBA : MIS : CH 8 2009
170 originate from some source and after being transformed by processes are received by some destinations. The source or destination of a data flow is called external entity. It is denoted by a rectangle. A circle or ellipse stands for a process that converts data into information. An open-end box represents a data store - data at rest, or a temporary repository of data. A square / rectangle defines a source (originator) or destination of system data.
DFDs are simple to draw and easily depicts the basic components of a system. It can be drawn in increasing level of detail, staring with a summary high level view and proceeding to more detailed lower level views. Thus, it supports modular, structured and top-down approach to design of information system The highest level of data flow diagram (level-O DFD) that depicts the summary of a system or process is called Context Diagram.
Consider a system for processing orders received from customers. The system after processing a customer's order sends either an order acceptance or an order rejection to the customer. The system also generates a sales report and sends it to the management. Here the customer and management are the external entities. The summary level-O DFD or Context Diagram of the above system is shown in figure.
Figure 1: Context diagram of Order Processing System
The same Context diagram can be depicted in greater detail by level-1 DFD as shown in figure 2. The "check order" process may result in rejection of order, whereas "enter order" process will result in acceptance of order. "Perform Sales Analysis" process will give rise to the sales report. All these processes are part of the "Order Processing" process in figure 1. In fact, level-l DFD contains four processes as a part of the "Order Processing" process', These are designated as
"check order", "2 enter order", "3 Update data file" and "4 Perform Sales Analysis" as shown in figure 2.
Srinivas MBA : MIS : CH 8 2009
171 Figure .2: Level.1 DFD of Order Processing System
Example 2 :
Let us consider another example of a bank system. The account holder gives payment (deposits) and receives payment receipt. The context diagram is shown in figure 3.
Figure 3: Context diagram of bank system
Level-1 DFD of the above Context diagram that depicts some greater detail of the process is shown in figure 4. Each of the above data flow diagram can be exploded into still detailed DFDs. For example the process-2 (update account) is shown in greater detail in level-2 DFD in figure 5. Thus a higher level DFD forms a parent-child relationship with its lower level DFDs.
Figure 4: Level-1 DFD of bank system
Srinivas MBA : MIS : CH 8 2009
172 Figure 5: Level-2 DFD ofprocess-2 (update account) of bank system
Note the way the processes are numbered in above DFD. This convention of numbering processes makes it easier for people to link it to its higher level.DFD.
This way of numbering is called leveling of DFDs. The process of leveling DFDs is illustrated in figure 6.
Physical and Logical DFD: DFD are of two types; i.e. Physical DFD and Logical DFD. The DFDs considered so far are examples of logical DFD. A logical DFD specifies various logical processes performed on - data. It does not specify who does the processing, where the processing is done or on which physical device data are stored. The above facts are specified by physical DFD. An example of physical DFD is shown in figure 7. It shows the process for withdrawal of money from bank by an account holder against withdrawal voucher. The DFD shows that the processing of withdrawal voucher is processed at five different desks.
Srinivas MBA : MIS : CH 8 2009
173 Fig 6 : The process of leveling DFDs is illustrated in figure 6.
Fig 7 : An example of physical DFD
Srinivas MBA : MIS : CH 8 2009
174 Example 3 :
Data Flow Diagram of Business Process : (Zero level)
Dispatch documents and bills
CUSTOM VENDO
Shipping - 4 Production
-
3Planning
-
2Marketing -1
5 Store
6 Purchase
7 Account Orders and
payments bills
demand
Schedule
requisition
Verified bills
Purchase Order
Material issue requisition
Finished goods transfer note
Shipment details
Payment
Goods Receipt
Srinivas MBA : MIS : CH 8 2009
175 Data Flow Diagram of Marketing Process : (First level)
CUSTOMER
1.1 Order registration
1.2 Demand forecasting
1.3 sales billing
Customer Order File
Bills Orders
Demand to Planning
Shipment Details from shipping