TUTORIAL IT

UNIVERSITY OF CALABAR, CALABAR
DEPARTMENT OF MATHS/STATISTICS & COMPUTER SCIENCE
SECOND SEMESTER EXAMINATION 2012/2013


COURSE: CSS 2222 – INTRODUCTION TO FILE PROCESSSING TIME: 3HOURS
INSTRUCTIONS: Answer any four (4) questions with two from each section


SECTION A
1. (a) (i) Discuss freely the concept of computer files and distinguish clearly between logical and physical records. (ii) What is a record key? Discuss its use in file processing.
(b). A magnetic tape that is 25 feet long has 2 feet of unusable portion. If density of this tape is 10 bytes/inches and blocking factor is 5, estimate the number of logical records of record length 95 bytes that can be stored in this tape if inter-block gap is 0.0025 inches.

2. (a) (i) Distinguish clearly a sequential file organization from a serial file organization.
(ii) Distinguish a Direct Access Storage (DASD) from Random Access Method (RAM).
(b) (i) What do you understand by the address of a record in a file? (ii) Describe two methods used to assign addresses to records in a file. (iii) What is file organization?

3. (a) (i) Discuss the storage and retrieval processes of ISAM and sequential file organizations.
(ii) State precisely the facilities in ISAM file organization that are not found in sequential files.
(iii) How do you use the additional facilities in ISAM file organization?
(b) (i) Distinguish between a master file and a transaction file. (ii) Suppose you have a master file M, and a transaction file T, both of which are sequentially sorted. Give an algorithm that uses T to update M in order to get new master NM.

SECTION B
4. (a) Using concrete examples, differentiate between files and directories, stating why each is important in its own right.
(b) In a multiuser system, there is almost always a requirement for allowing file sharing among users, describe any five (5) access rights in the light on this.

5. (a) You have been handed the task of making a small presentation on file allocation schemes at the forthcoming orientation for Computer Science students in our Department. You are to use the following files to demonstrate contiguous allocation: HOD_Admin.xls (length=5), Students.mdb (length=9), AcadStaff.doc (length=5), AdimStaff.pdf (lenth=7) and NUDCB.html (lenth=8) in that order. Starting your allocation at block 2; (i) Show how this allocation will be done on disk (ii) Construct a directory table showing how these files will be allocated.

(b) (i) Sow how the file AdimStaff.pdf will be allocated using chained and indexed allocation schemes, respectively. (ii) Make brief comments on external fragmentation stating why it is prevalent in contiguous allocation.

6. (a) Typical of computer installation management, describe with examples, any three (3) ways in which you can provide file security.
(b) You have been handed four record keys: 876-54-3210, 123-45-6789, 187-65-2243, and 101-20-3037 to place in a database file that contains a maximum of twelve records. Using the modulus hashing technique/algorithm, show how these records will be placed in the file.