Ch03_slides

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CICS, C3 2001, Mike Murach & Associates, Inc. Slide 1

Chapter 3

How to designa CICS program


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Objectives1. Explain why event-driven program design is appropriate for pseudo-conversational CICS programs.

2. Given specifications for a CICS program, create a list of each user

input event that can trigger execution of the program, identify the

various contexts the program must manage, and create a summaryof the programs response to each event.

3. Working from an event/response chart such as the one in figure 3-4,

create a program structure chart that indicates the major event-

processing modules and the major functional modules subordinate

to each event-processing module.


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The program overview for the customermaintenance programProgram CUSTMNT1: Customer maintenance

Trans-id MNT1

Overview Maintain customer information in the customer master file by allowing

the user to enter new customers, change existing customers, or delete

existing customers.

Input/output

specifications

CUSTMAS Customer master file

MNTMAP1 Customer maintenance key map

MNTMAP2 Customer maintenance data map

Processing

specifications

1.Control is transferred to this program via XCTL from the menu

program INVMENU with no communication area. The user can also

start the program by entering the trans-id MNT1. In either case, theprogram should respond by displaying the key map.


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The program overview for the customermaintenance program (continued)

Processingspecifications

2.On the key map, the user enters a customer number and selects aprocessing action. If the user selects Add, the customer number

entered must not exist in the file. For Change or Delete, the

customer number must exist in the file. If a valid combination isnt

entered, an error message should be displayed.

3.If the user enters a valid combination of action and customer

number, the program displays the data map. For an add operation,the user can then enter the customer information. For a change

operation, the user can change any of the existing information. For a

delete operation, all fields should be set to protected so the user

cant enter changes. To complete any of these operations, the user

must press the Enter key.

4.If the user presses PF3 from either map, return to the menu programINVMENU by issuing an XCTL command. If the user presses PF12

from the key map, return to the menu program. However, if the user

presses PF12 from the data map, redisplay the key map without

completing the current operation.


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The copy member for the customer master record(CUSTMAS)

01 CUSTOMER-MASTER-RECORD.

*

05 CM-CUSTOMER-NUMBER PIC X(6).

05 CM-FIRST-NAME PIC X(20).

05 CM-LAST-NAME PIC X(30).

05 CM-ADDRESS PIC X(30).

05 CM-CITY PIC X(20).

05 CM-STATE PIC X(2).

05 CM-ZIP-CODE PIC X(10).

*


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The screen layout for the key map


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The screen layout for the data map


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How to create an event/response chart

Identify the events that can cause the program to be started, and

identify in general terms how the program should respond to eachof those events.

Be sure to include a response to the user action that causes theprogram to be started for the first time. A program typically

responds to this event by displaying the first map and then

ending.

If the final step in a response is to return control to CICS, you canomit this step from the event/response chart and it will be

assumed.

Identify the contextof each event (if any), then add the contexts

to the event/response chart and expand the response processing.

If the response to an event causes a change in the context,indicate the new context in the event/response chart.


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A beginning event/response chart for thecustomer maintenance program

Event Response

Start the program Display the key map.

PF3 Transfer control to the menu program.

PF12 If the key map is displayed

transfer control to the menu program.

If the data map is displayedcancel the operation and display the key map.

Enter If the key map is displayed

prepare the data map according to the requested action and

display it.

If the data map is displayed

add, change, or delete the customer as appropriate.

Clear Redisplay the current map without any data.

PA1, PA2, or PA3 Ignore the key.

Any other key Display an appropriate error message.


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Event contexts for the customer maintenanceprogramContext Explanation

Get key The key map is displayed, awaiting input of a valid combination of

action code and customer number.

Add customer The data map is displayed in response to a request to add a customer.

Change customer The data map is displayed in response to a request to change a

customer.

Delete customer The data map is displayed in response to a request to delete a

customer.


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The final event/response chart for the customer

maintenance programEvent Context Response New context

Start the

program

n/a Display the key map. Get key

PF3 All Transfer control to the menu program. n/a

PF12 Get key Transfer control to the menu program. n/a

Add customer

Change customer

Delete customer

Cancel the operation and display the key

map.

Get key

Enter Get key Edit input data.

If valid

display data map

else

display an error message.

Add customer,

Change customer,

or Delete customer

Get key


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maintenance program (continued)Event Context Response New context

Enter Add customer Add the customer record.

If not duplicate record

display the key map with a

completion message

else display the key map with an error

message.

Get key

Get key

Change customer Change the customer record.

If record found


completion message

else

display the key map with an errormessage.

Get key

Get key


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maintenance program (continued)Event Context Response New context

Enter Delete customer Delete the customer record.

If record found


completion message

else

display the key map with an errormessage.

Get key

Get key

Clear Get key Redisplay the key map. Unchanged

Add, Change, or

Delete customer

Redisplay the data map with unprotected

data erased.

Unchanged

PA1, PA2,

or PA3

All Ignore the key. Unchanged

Any other

key

All Display an appropriate error message. Unchanged


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A general procedure for designing the first twolevels of a structure chart

1. Draw the top-level module and give it a name that represents theentire program.

2. Decide what event processing should be implemented as separatemodules, and draw a box subordinate to the top-level module for

each one.


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How to determine what modules should make up

the second level of a structure chart If the programs response to an event includes receiving data from

the terminal, processing it, and sending data back to the terminal,

create a separate module for the event.

If the programs response to an event doesnt include receiving

data from the terminal, consider creating a separate module only ifthe response requires more than a few COBOL statements to

implement.

If the COBOL statements for implementing the top-level modulerequire more than a page or two, consider creating additional

second-level modules to simplify the coding in the top-levelmodule.


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The first two levels of the structure chartfor the customer maintenance program

Process

customermaintenance

Process

changecustomer

Process

addcustomer

Process

keymap

Process

deletecustomer


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An alternative design for the customermaintenance program

Processkeymap

Processaddcustomer

Processchangecustomer

Processdeletecustomer

Processdatamap

Processcustomermaintenance


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A general procedure for designing one leg of astructure chart

1. Draw one subordinate module for each function that the controlmodule at the top of the leg needs to do.

2. Use the same thought process for the next level of modules. Ifany of them require more than one function, draw one

subordinate module for each function.

3. If necessary, continue this process until each of the lowest-levelmodules consists of just one function.


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Guidelines for designing the legs of a structurechart

Each module should represent one and only one function. The function of a called module must be logically contained in the

function of its calling module.

The code in each module should be manageable. Use a generalized send module for each map. Each module will

contain one or more SEND MAP commands with various options.

Include a separate module for each file I/O statement so thestatements are easy to locate and modify.


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The process-key-map leg of the customer

maintenance program

Processkeymap

Editkeydata

Senddatamap

Sendkeymap

Receivekeymap

Readcustomerrecord


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The final structure chart for the customer maintenanceprogram

Senddatamap

Sendkeymap

Receivekeymap

Editkeydata

Processaddcustomer

Writecustomerrecord

Receivedatamap

Sendkeymap

Sendkey

map

Rewritecustomer

record

Readcustomer

for update

Receivedata

map

Readcustomerfor update

Deletecustomerrecord

Sendkeymap

Processchangecustomer

Processdeletecustomer

Readcustomer

record

Process

customermaintenance

Processkeymap

Senddatamap

Sendkeymap

0000

1000 2000 3000 4000 1400 1500

1100 1200 1400 1500

1300

2100 2300 1500

2100 3100 3200 1500

3100 4100 1500


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How to identify common modules

To identify a common module (a module that appears more thanonce in a structure chart), shade its upper right corner.

If a common module has subordinate modules, you need to includethem only once on the chart.

How to identify linked or called programs To identify a linked program (a program thats executed using the

LINK command), add a module to the structure chart. Include a

stripe at the top of the module that gives the program name.

Use the same technique to identify a called program (a programthats executed using the COBOL Call statement).


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How to number the modules in a structure chart

Use 000 or 0000 for the top-level module.

Number the modules in the second level from left to right leavinglarge enough gaps for subordinate modules.

After the first two levels, number the modules down each leg inappropriate increments.

When you code the COBOL paragraph for each module later on,the paragraph name will be the module number followed by the

module name.


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How to create a structure listing A structure listing is an outline that uses indentation to show the

levels of the modules. The letter C in parentheses can be used to

identify common modules.

When youre designing a program, use the outline feature of anymodern word processor to prepare a structure listing. This feature

makes it easy to analyze the structure and reorganize the listing.

When a program is finished, you can use a structure listingprogram to generate a structure listing from the COBOL code for

the finished program.


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A structure listing for the customer maintenanceprogram0000-PROCESS-CUSTOMER-MAINT

1000-PROCESS-KEY-MAP

1100-RECEIVE-KEY-MAP

1200-EDIT-KEY-MAP

1300-READ-CUSTOMER-RECORD

1400-SEND-DATA-MAP (C)

1500-SEND-KEY-MAP (C)

2000-PROCESS-ADD-CUSTOMER

2100-RECEIVE-DATA-MAP (C)

2300-WRITE-CUSTOMER-RECORD


3000-PROCESS-CHANGE-CUSTOMER

2100-RECEIVE-DATA-MAP (C)

3100-READ-CUSTOMER-FOR-UPDATE (C)

3200-REWRITE-CUSTOMER-RECORD


4000-PROCESS-DELETE-CUSTOMER

3100-READ-CUSTOMER-FOR-UPDATE (C)

4100-DELETE-CUSTOMER-RECORD


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