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Computer Science 255






Final Exam






Name _______________________








Monday, Dec. 11
200 pts.

I.	Basic stuff

a.	(5 pts.)	What do the letters in COBOL stand for?





b.	(5 pts. each)	Give brief definitions:

	1.	File




	2.	Entity




	3.	CODASYL




	4.	Data Flow Diagram




	5.	Projection operation (as in the relational algebra)





	6.	Level break program





c.	(25 pts.)	We have studied three file organizations this term 
(sequential, relative, and indexed files).  Briefly describe each, 
giving a significant advantage of using each organization.


d.	(20 pts.)	The argument has been made that business data 
processing is a software engineering discipline, and that the 
life cycle model for software development is particularly well 
suited for business data processing.  List and briefly describe 
the five steps in the life cycle model for software 
development.

e.	(20 pts.)	Given the following:

01	CLASS-TABLE.
	02	STUDENT-REC OCCURS 30 TIMES.
		03	STUDENT-NAME	PIC X(20).
		03	EXAM OCCURS 3 TIMES PIC 999.
		03	EXAM-AVERAGE	PIC 999V99.

	Write the COBOL code necessary to calculate for each of the 30 
students the average of each student's three exam scores and 
place the result in the EXAM-AVERAGE field for the student.  
That is, suppose that the STUDENT-NAME and EXAM entries in 
the array have been filled - write the code to fill the EXAM-
AVERAGE entry for each student.

II.	Sequential files.  (30 pts.)

	On the following page, do one (but only one) of the following 
two problems (a or b):

a.	The sequential file CUSTOMER-CHARGES contains records 
as follows:

	01	CUSTOMER-REC.
		02	CNO	PIC 9(5).
		02	CHARGE	PIC 999V99.

	The file is sorted by CNO, and has a sentinel record with
	CNO = 99999.

	Write the code necessary to print, for each customer, the 
customer's name and total charges (not each charge - 
only the total).  Check that the records are indeed in 
sequence, and DISPLAY an error message and take 
appropriate action if an out-of-sequence condition is 
discovered.

b.	The sequential file CUSTOMER-FILE contains records as 
follows:

	01	CUSTOMER-REC.
		02	CNO		PIC 9(5).
		02	CNAME	PIC X(20).
		02	CURRENT-CHARGES	PIC 999V99.

	The sequential file CUSTOMER-CHARGES is as in part (a).  
Both files are sorted by CNO, and both have sentinel 
records with CNO=99999.  

	Write the code necessary to read both files and produce 
an updated file reflecting the charges made by a 
customer.  Reject (and DISPLAY an error message) charge 
records for which there does not exist a corresponding 
customer.  Sequence checking is not necessary with this 
problem.

Workspace for problem II.

III	Indexed files.	

	a.	Consider the entity-relationship diagram given below for 
tapes rented to customers by a video store.  TNO is the key for 
the TAPE file, and CNO is the key for the CUSTOMER file.:
                                                          

	The following files were recommended to implement this 
diagram:

		TAPE(TNO, TNAME)
		CUSTOMER(CNO, CNAME)
		RENT(CNO, TNO, DAYS)

	a.	(15 pts.)	Identify, by file

		i.	Primary keys

			TAPE

			CUSTOMER

			RENT


		ii.	Foreign keys (list file and fields)

	


b.	(10 pts.)	Write a FD statement and a SELECT statement 
for the RENT file.  Use reasonable data types and lengths.




c.	(10 pts.)	Assuming reasonable FD and SELECT 
statements for the CUSTOMER file, write the COBOL 
statements necessary to read the unique record for 
customer "C12345" and DISPLAY that customer's name.


d.	(15 pts.)	Using your answer to part (b) and assuming 
reasonable FD and SELECT statements for the other two 
files, write the COBOL statements to list the tapes 
rented by the customer with CNO = "C12345".



IV.	Relative files (20 pts.)

	The file EMP-FILE is a relative file (RELATIVE KEY EMP-FILE-
KEY) with records organized as follows:

	01	EMP-REC.
		02	ENO	PIC X(5).
		02	ENAME	PIC X(10).
		02	NEXT-EMP	PIC 999.

	NEXT-EMP is the record number of the next record in the file.  
Record number 1 is a list header record with ENO = "99999" and 
NEXT-EMP containing the record number of the first "real" 
record in the file (as with the order invoice exercise).  The 
final record in the list has a NEXT-EMP value of 1 (pointing 
back to the sentinel record).

	Assuming that the file is open, write the COBOL code 
necessary to read the file in the order given by the NEXT-EMP 
links and DISPLAY each ENAME in turn.