HP 3000 Manuals

COBOL/HP-UX Operating Guide for the Series 700 and 800

Running the Demonstration Programs 

To run the demonstration programs you must first of all install the COBOL
system software on your multi-user UNIX system following the instructions
given in your Read This First  card.

When you have done this, compile the programs mudemo.cbl, stockin.cbl,
stockout.cbl, stockioa.cbl and stockiom.cbl using the following command:

     cob -u mudemo.cbl stockin.cbl stockout.cbl
        stockioa.cbl stockiom.cbl

Move the resulting generated code modules mudemo.gnt, stockin.gnt,
stockout.gnt, stockioa.gnt and stockiom.gnt to an area where operators on
both terminals can access them.  You must also make sure that both
operators are accessing the same file.

To run the multi-user demonstration programs enter:

     cobrun mudemo

on both terminals.  Both screens display the initial screen as shown in
Figure 16-1 .


          Figure 16-1.  Initial Screen 

When the initial screen is displayed, the operator must choose the access
and lock mode by pressing the number associated with the required mode,
followed by Enter.  When the operator has chosen, the relevant subprogram
is called by the main program mudemo, and another screen is displayed.
This screen shows a "Stock Control System" with stock code, stock
description, stock held and cost per unit.  The bottom of the screen
shows the open and lock modes, what the last operation was and whether it
was successful, and the file status.  Again, there is a choice of
operations the operator may want to perform.

Creating the File 

The first thing you must do to set up the multi-user environment is to
create a data file that the two operators can share.  One operator must
create this file by selecting input choice 4 to open the file for output.


          Figure 16-2.  Screen to Create a New Record 

When the screen shown in Figure 16-2  is displayed, this operator
should enter data in the stock code, stock description, stock held and
cost per unit fields using the Tab key to move to forwards from field to
field.

When this operator has entered data into these fields, this data can be
written into the data file mustock.dat by writing the record.  To do
this, select option 1 (write record) and press Enter.  We suggest that
this operator writes five or six records in this way and then closes the
file by exiting (selecting option 2).

While the first operator is doing this, the second operator can try to
access the data file mustock.dat, but the second operator will fail to
gain access to this file at all.  This is because opening a file for
output locks the file exclusively.  The second operator will receive a
"file locked" status.

Now that the operators have a data file they can share you can have them
both accessing the data file mustock.dat at the same time.

Sharing the File 

If operator one selects 2, for I-O Lock Mode Automatic at the initial
screen, the new screen is displayed as shown in Figure 16-3 .  To
access the first record, the operator must move down to the Input Choice 
field by pressing End twice.  Now press 2 to read the next record.  The
first record in mustock.dat is displayed.


          Figure 16-3.  Preparing to Read the Next Record 

The first record in the data file mustock.dat is now locked by operator
one, and remains so until this operator next accesses the file.  Operator
two can access any other record in the file by also selecting to open the
file for I-O Lock Mode Automatic or for Input, for example.  Operator two
can execute a "start not less than", thus avoiding the first record in
the file that is locked to operator one.

Operator two may access the first record, but receives a file status of
"Record locked" and the access is unsuccessful.  However, the data will
be returned unless the operating system does not support this.

Try the various combinations of locking and access for yourself so that
you become familiar with the way Micro Focus COBOL can lock data.

MPE/iX 5.0 Documentation