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Computer Science 255


Second Hour Exam




Name ______________________

















Thursday, Oct. 3
90 pts.



1.	(15 pts.) Explain what a file buffer is, the role that it 
plays, and the value of multiple buffering.























2.	(5 pts.)	How would you specify a blocking factor of 5 
for the file EMP-FILE (EMP.DAT)?







3.	(5 pts.)
	Consider the following sequence of keys:

	10,14,16,3,17,19,12,3,18,42,91,88,90

	What would the sequence of keys look like after the first 
distribution/merge phase of a mergesort?













4.	(5 pts.)	What is a key field?



4.	(30 pts.)	Suppose that the file WORK-STUDY contains records 
with the following organization:

01	WORK-STUDY-REC.
	02	STUDENT-NO	PIC X(5).
	02	STUDENT-NAME	PIC X(10).
	02	HOURS		PIC 99.
	02	RATE		PIC 99V99.

	The records are sorted by STUDENT-NO (which is the key for 
this record).  A given student may have several records in the 
file.  Write the procedure division entries necessary to read the 
records in the file and produce, for each student, a detail line 
with the student's name and total pay.  Assume reasonable 
names for data division entries (i.e., you do not need to write 
data division entries).



Additional work space for problem 4


5.	(30 pts.)

	The file MAJOR-FILE contains 20 records organized as follows:

	01	MAJOR-REC.
		02	MAJOR	PIC X(10).
		02	DEPT		PIC X(10).


a.	Write the DATA DIVISION entry necessary to create a 
table of 20 entries of this record type ordered in 
ascending order by MAJOR.  Arrange things so that you 
can use a binary search on the table.











b.	Write the code necessary to load the table with records 
from the file














c.	Using the COBOL binary search verb, write the code 
necessary to search the table for the major "CSB" and 
display the name of the department if found.  If not 
found, print an error message.