Using Loops in Programming
Flowcharts and Pseudocode
Please use speaker notes for
additional information!
condition
Y
processing
N
DO WHILE LOOP:
The while loop shown here tests a
condition to see if the processing
should be done.
If the answer to the condition is
YES, the processing box shown is
executed.
If the answer to the condition is
NO, the processing box shown is
not executed.
DO UNTIL LOOP:
The while loop shown here
executes the processing once and
then tests a condition to see if the
processing should be done.
processing
condition
N
Y
This means that the loop will
always be executed once since it is
executed before checking is done.
Once the processing has been done
once, further processing is
determined by the answer to the
condition.
If the condition gets a YES, then
the processing is executed again.
If the condition gets a NO, then the
processing is not executed again.
DO WHILE LOOP
taxCt = 1
taxCt < 5
Y
Set up tax bill
Print tax bill
Add 1 to
taxCt
N
The looping structure where I want to use the while loop to do something
a certain number of times, requires the following:
• initialize the counter outside the loop
• test the counter to determine whether or not to enter the loop
• increment the counter inside the loop
taxCt = 1
taxCt < 5
Y
Set up tax bill
Print tax bill
N
Pseudocode:
taxCt = 1
while taxCt < 5
set up tax bil (move information to bill)
print tax bill
add 1 to taxCt
end-loop
Add 1 to
taxCt
Start
Process
Housekeeping
Read a record
Process
Not
EOF
Y
The loop shown here is
executed until there are
no more records on the
file.
Loop
Terminate
End-Process
Stop
Housekeeping
Terminate
Setup data
Close files
Open files
End-Terminate
End-Housekeeping
The loop is
shown on the
next slide.
DO WHILE LOOP
DO WHILE LOOP
Loop
Set up tax bill
information
taxCt = 1
taxCt < 5
Y
Set up tax bill
Print tax bill
N
Read a record
End-Loop
The loop shown on this
page prints 4 tax bills for
each property owner.
Add 1 to
taxCt
Pseudocode
Mainline
housekeeping()
process()
terminate()
stop
end-mainline
Housekeeping()
set up data
open files
return
end-housekeeping
Terminate()
close files
return
end-terminate
Process()
read a record
while not end of file
loop()
end-loop
return
end-process
Loop()
set up tax bill information
taxCt = 1
while taxCt < 5
set up tax bill with
additional data if needed
print tax bill
add 1 to taxCt
end-loop
read a record
return
end-loop
Start
Housekeeping
Housekeeping
Setup variables
Process
Enter money
you have to
pay bills
Wrapup
Stop
Accept
amountAvail
End-Housekeeping
Wrapup
May not have
paid last billcheck
Cannot pay
any more bills moneyAvail
End-Wrapup
Process is on the
next page,
Process
Because I want to keep
this processing simple,
the user must enter the
smallest bill first and
move to the largest. So
when a bill cannot be
paid, processing is
done.
Enter
amountBill
& payTo
Accept
amountBill
& payTo
amountBill
< moneyAvail
N
End-Process
Y
Loop
Note that the only
way out of this loop
is to have a bill you
cannot afford to
pay. This means if
you have no more
bills to pay, entering
a large number more than
moneyAvail will
cause an exit.
DO WHILE LOOP
Loop
Set up information
to pay bill
Pay bill
Because I want to keep
this processing simple,
the user must enter the
smallest bill first and
move to the largest. So
when a bill cannot be
paid, processing is
done.
Subtract amountBill
from moneyAvail
Ask for amountBill
& payTo
Accept amountBill
& payTo
End-Loop
This is where I take in more
data. I will then go back to
process where I do the loop if I
have the money to pay the bill.
Mainline
housekeeping()
process()
wrapup()
stop
end-mainline
Housekeeping()
set up data
enter money you have
to pay bills
accept amountAvail
return
end-housekeeping
Wrapup()
print msg about last bill
print msg about moneyAvail
return
end-wrapup
Process()
enter amountBill
enter payTo
accept amountBill & toPay
While amountBill < moneyAvail
loop
end-loop
return
end-process
Loop()
set up information to pay bill
print paid bill
subtract amountBill from
money Avail
enter amountBill
enter payTo
accept amountBill & payTo
return
end-loop
IDENTIFICATION DIVISION.
PROGRAM-ID. C17LOOP.
*ENVIRONMENT DIVISION.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 INPUT-VARIABLES.
05 AMOUNT-AVAIL
05 AMOUNT-BILL
05 PAY-TO
01 OUTPUT-VARIABLES.
05 AMOUNT-BILL-TO-SCR
05 AMOUNT-AVAIL-TO-SCR
The numbers are input as pure numbers.
The V remembers where the decimal
point is if the user inputs decimal points.
PIC 9(5)V99.
PIC 9(5)V99.
PIC X(20).
PIC $$$,$$$.99.
PIC $$$,$$$.99.
Housekeeping
Setup variables
On this slide, I have shown the beginning of the
COBOL program. The PROCEDURE
DIVISION where the actual processing is done is
shown on the next slide.
This would correspond to setting up variables.
The output wants to include
decimal points and commas if
needed. I setup these pictures to
show the edited data I will display
on the screen.
PROCEDURE DIVISION.
MAINLINE.
PERFORM A-100-HOUSEKEEPING.
PERFORM B-100-PROCESS.
PERFORM C-100-WRAPUP.
STOP RUN.
A-100-HOUSEKEEPING.
DISPLAY " " WITH BLANK SCREEN.
DISPLAY " ".
DISPLAY "ENTER THE AMOUNT OF MONEY AVAILABLE".
ACCEPT AMOUNT-AVAIL.
B-100-PROCESS.
DISPLAY "ENTER THE AMOUNT OF THE FIRST BILL".
ACCEPT AMOUNT-BILL.
DISPLAY "ENTER WHO TO PAY THE BILL TO"
ACCEPT PAY-TO.
PERFORM B-200-LOOP
UNTIL AMOUNT-BILL > AMOUNT-AVAIL.
B-200-LOOP.
DISPLAY "YOU HAVE PAID THE BILL TO " PAY-TO.
MOVE AMOUNT-BILL TO AMOUNT-BILL-TO-SCR.
DISPLAY "PAID THIS AMOUNT: "AMOUNT-BILL-TO-SCR.
SUBTRACT AMOUNT-BILL FROM AMOUNT-AVAIL.
DISPLAY " ".
DISPLAY "ENTER THE AMOUNT OF THE NEXT BILL".
DISPLAY "ENTER THE SMALLEST BILL LEFT TO PAY"
ACCEPT AMOUNT-BILL.
DISPLAY "ENTER WHO TO PAY THE BILL TO".
ACCEPT PAY-TO.
C-100-WRAPUP.
DISPLAY "YOU MAY NOT HAVE PAID THE LAST BILL".
DISPLAY "CHECK THE LISTINGS ON THE SCREEN".
DISPLAY "CANNOT PAY ANY MORE BILLS".
MOVE AMOUNT-AVAIL TO AMOUNT-AVAIL-TO-SCR
DISPLAY "THIS IS WHAT YOU HAVE LEFT " AMOUNT-AVAIL-TO-SCR.
PROCEDURE DIVISION.
MAINLINE.
PERFORM A-100-HOUSEKEEPING.
PERFORM B-100-PROCESS.
PERFORM C-100-WRAPUP.
STOP RUN.
A-100-HOUSEKEEPING.
DISPLAY " " WITH BLANK SCREEN.
DISPLAY " ".
DISPLAY "ENTER THE AMOUNT OF MONEY AVAILABLE".
ACCEPT AMOUNT-AVAIL.
Housekeeping
Start
Setup variables
Housekeeping
Enter money
you have to
pay bills
Process
Wrapup
Stop
Accept
amountAvail
End-Housekeeping
Process
Enter
amountBill
& payTo
B-100-PROCESS.
DISPLAY "ENTER THE AMOUNT OF THE FIRST BILL".
ACCEPT AMOUNT-BILL.
DISPLAY "ENTER WHO TO PAY THE BILL TO"
ACCEPT PAY-TO.
PERFORM B-200-LOOP
UNTIL AMOUNT-BILL > AMOUNT-AVAIL.
Note that in the flowchart I said
if amountBill is < moneyAvail
execute the loop.
Accept
amountBill
& payTo
amountBill
< moneyAvail
N
End-Process
In the code it is expressed
differently, here I say do the loop
until the amountBill is greater
than the amountAvail.
Y
Loop
Essentially, I am saying the same
thing but the language of
COBOL led me to express it
differently.
Loop
Set up information
to pay bill
Pay bill
Subtract amountBill
from moneyAvail
Ask for amountBill
& payTo
Accept amountBill
& payTo
End-Loop
B-200-LOOP.
DISPLAY "YOU HAVE PAID THE BILL TO " PAY-TO.
MOVE AMOUNT-BILL TO AMOUNT-BILL-TO-SCR.
DISPLAY "PAID THIS AMOUNT: "AMOUNT-BILL-TO-SCR.
SUBTRACT AMOUNT-BILL FROM AMOUNT-AVAIL.
DISPLAY " ".
DISPLAY "ENTER THE AMOUNT OF THE NEXT BILL".
DISPLAY "ENTER THE SMALLEST BILL LEFT TO PAY"
ACCEPT AMOUNT-BILL.
DISPLAY "ENTER WHO TO PAY THE BILL TO".
ACCEPT PAY-TO.
C-100-WRAPUP.
DISPLAY "YOU MAY NOT HAVE PAID THE LAST BILL".
DISPLAY "CHECK THE LISTINGS ON THE SCREEN".
DISPLAY "CANNOT PAY ANY MORE BILLS".
MOVE AMOUNT-AVAIL TO AMOUNT-AVAIL-TO-SCR.
DISPLAY "THIS IS WHAT YOU HAVE LEFT " AMOUNT-AVAIL-TO-SCR.
Wrapup
May not have
paid last bill check
Cannot pay
any more bills
- moneyAvail
End-Wrapup
I entered that the
amount of money
available was 10000
Now I am being prompted to
enter the next bill.
Then I entered the
amount of the first bill
for 1275.25 and that it
was to be paid to JM
Builders. The pament
was confirmed.
Now I have paid my second
bill for 3000.
This shows the next payment
to Heights Roofers.
I then attempted to pay H&J
Builders 6000 but I did not
have that amount left and the
bill was not paid. I know this
because I received no
confirmation of payment and
the message that the last bill
may not have been paid. I also
show the amount of money left.
Start
Process
Housekeeping
Read a record
Process
Not
EOF
Y
The loop shown here is
executed until there are
no more records on the
file.
Loop
Wrapup
End-Process
Stop
Wrapup
Housekeeping
The loop is
shown on the
next slide.
Set up total line
Setup data
Write total line
Open files
Close files
End-Housekeeping
End-Wrapup
Note that I am
writing a total line
when I Wrapup this
program. I a set up
and then I write.
DO WHILE LOOP
Loop
N
JBCD=S
Y
Add SAL to
TOTAL-SAL
Set up the
screen line
Write to
the screen
Read a record
End-Loop
Mainline
housekeeping()
process()
terminate()
stop
end-mainline
Housekeeping()
set up data
open files
return
end-housekeeping
Terminate()
set up total line
write total line
close files
return
end-terminate
Process()
read a record
while not end of file
loop()
end-loop
return
end-process
Loop()
if JBCD equals “S”
add sal to total-sal
set up the screen
line
write the screen line
end-if
read a record
return
end-loop
IDENTIFICATION DIVISION.
PROGRAM-ID. CIS17lab.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT EMPLOYEE-FILE
ASSIGN TO "A:\EMPLOYEE.DAT".
DATA DIVISION.
FILE SECTION.
FD EMPLOYEE-FILE
DATA RECORD IS EMPLOYEE-RECORD.
01 EMPLOYEE-RECORD.
Layout of the input
05 IDNO
PIC XXXXX.
05 EMPNAME
PIC X(20).
am reading.
05 YRBTH
PIC 9(4).
05 GEN
PIC X.
05 MARSTAT
PIC X.
05 NUMDEP
PIC 99.
05 ED
PIC XXX.
05 JBCD
PIC X.
05 PAYHR
PIC 999V99.
05 SAL
PIC 9(6)V99.
05 BONUS
PIC 9(5).
05 DEPT
PIC 99.
05 STATE
PIC XX.
WORKING-STORAGE SECTION.
01 PROG-INDICATORS.
05 END-OF-FILE-IND
PIC XXX VALUE "NO ".
01 WORK-AREAS.
05 TOTAL-SAL
PIC 9(8)V99
VALUE 0.
01 OUTPUT-TO-SCR.
05 SAL-FOR-SCR
PIC $$$$,$$$.99.
05 TOTAL-SAL-FOR-SCR PIC $$$,$$$,$$$.99.
Housekeeping
Setup data
file I
Area to accumulate totals.
Area to layout fields that will
appear on the screen.
PROCEDURE DIVISION.
MAINLINE.
PERFORM A-100-HOUSEKEEPING.
PERFORM B-100-PROCESS.
PERFORM C-100-WRAPUP.
STOP RUN.
A-100-HOUSEKEEPING.
OPEN INPUT EMPLOYEE-FILE.
DISPLAY " " WITH BLANK SCREEN.
DISPLAY " ".
B-100-PROCESS.
READ EMPLOYEE-FILE
AT END
MOVE "YES" TO END-OF-FILE-IND.
PERFORM B-200-LOOP
UNTIL END-OF-FILE-IND = "YES".
B-200-LOOP.
IF JBCD = "S"
ADD SAL TO TOTAL-SAL
MOVE SAL TO SAL-FOR-SCR
DISPLAY EMPNAME "
" JBCD "
" SAL-FOR-SCR
END-IF
READ EMPLOYEE-FILE
AT END
MOVE "YES" TO END-OF-FILE-IND.
C-100-WRAPUP.
DISPLAY " ".
MOVE TOTAL-SAL TO TOTAL-SAL-FOR-SCR.
DISPLAY "TOTAL SALARY FOR SALARIED EMPLOYEES "
TOTAL-SAL-FOR-SCR.
CLOSE EMPLOYEE-FILE.
PROCEDURE DIVISION.
MAINLINE.
PERFORM A-100-HOUSEKEEPING.
PERFORM B-100-PROCESS.
PERFORM C-100-WRAPUP.
STOP RUN.
A-100-HOUSEKEEPING.
OPEN INPUT EMPLOYEE-FILE.
DISPLAY " " WITH BLANK SCREEN.
DISPLAY " ".
Start
Housekeeping
Process
Wrapup
Housekeeping
Setup data
Open files
End-Housekeeping
Stop
B-100-PROCESS.
READ EMPLOYEE-FILE
AT END
MOVE "YES" TO END-OF-FILE-IND.
PERFORM B-200-LOOP
UNTIL END-OF-FILE-IND = “YES”.
Process
Read a record
Not
EOF
End-Process
Y
Loop
B-200-LOOP.
IF JBCD = "S"
ADD SAL TO TOTAL-SAL
MOVE SAL TO SAL-FOR-SCR
DISPLAY EMPNAME "
" JBCD "
" SAL-FOR-SCR
END-IF
READ EMPLOYEE-FILE
N
AT END
MOVE "YES" TO END-OF-FILE-IND.
Loop
JBCD=S
Y
Add SAL to
TOTAL-SAL
Set up the
screen line
Write to
the screen
Read a record
End-Loop
C-100-WRAPUP.
DISPLAY " ".
MOVE TOTAL-SAL TO TOTAL-SAL-FOR-SCR.
DISPLAY "TOTAL SALARY FOR SALARIED EMPLOYEES "
TOTAL-SAL-FOR-SCR.
CLOSE EMPLOYEE-FILE.
Wrapup
Write total line
Close files
End-Wrapup