Lesson Notes By Weeks and Term - Senior Secondary 2
Handling computer files
Handling computer files
Term: 2nd Term
Week: 2
Class: Senior Secondary School 2
Age: 16 years
Duration: 40 minutes of 2 periods each
Date:
Subject: Data Processing
Topic:- Handling computer files
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, pictures, Data Processing for senior Secondary Education by Hiit Plc, WAPB Computer Studies for Senior Secondary I by Adekunle et al, On-line Materials.
INSTRUCTIONAL PROCEDURES
PERIOD 1-2
|
PRESENTATION |
TEACHER’S ACTIVITY |
STUDENT’S ACTIVITY |
|
STEP 1 INTRODUCTION |
The teacher reviews the previous lesson on the concept of computer files |
Students pay attention |
|
STEP 2 EXPLANATION |
He outlines the basic operations that could be carried out on computer files. He also highlights the steps in creating a sequential file
|
Students pay attention and participates |
|
STEP 3 DEMONSTRATION |
He discusses the concept of file insecurity; its effects and control and distinguishes between manual and computer files |
Students pay attention and participate |
|
STEP 4 NOTE TAKING |
The teacher writes a summarized note on the board |
The students copy the note in their books |
NOTE
BASIC OPERATIONS WE CAN CARRY OUT ON COMPUTER FILES
Create: Creating a file with a given name.
Delete: Deleting a file that are unwanted.
Retrieve: Retrieving a stored file or lost file.
Copy: Copying a created file to either an external or in-built storage device.
View: Viewing a created file or granting privilege of viewing.
Open: Opening a file to use its contents.
Update: Reading or updating the contents.
Close: Closing the file, thereby losing access until it is opened again.
STEPS IN CREATING SEQUENTIAL FILE:
The OPEN statement is used in writing information to a file. In general, the open statement follows this pattern;
OPEN file FOR OUTPUT AS 1
The file determines the filename to use
The FOR portion indicates how the file will be accessed or operated; it may be APPEND, BINARY, INPUT, OUTPUT, and RANDOM
The AS is the identifier used for the file handle in question.
The following opens a file, using mode OUTPUT and number 1, and then saves the text.
10 CLS
20 OPEN “textfile.dat” FOR OUTPUT AS 1
30 PRINT 1, “Hello World”
40 CLOSE 1
50 END
CODE
The combination of all these records forms a file. Thus, a file is a group of related records.
To facilitate the retrieval of specific records from a file, at least one field in each record is chosen as record key. Usually, the key is unique to every record to avoid duplication of records in a file.
BASIC File Processing statement to read and display files
The table below would be used in a BASIC program. The table would be stored in a file named “EXAMFILE.TXT” the content would be retrieved from the file and output to the screen
|
|
MATHEMATICS |
ENGLISH |
TOTAL SCORE |
|
01234 |
50 |
90 |
140 |
|
01235 |
70 |
40 |
110 |
|
01236 |
80 |
70 |
150 |
Example
10 CLS
20 OPEN “EXAMFILE.TXT” FOR INPUT AS 1
30 PRINT 1 “MATRIC NO. MATHS ENG. LANG TOTAL SCORE”
40 PRINT 1 “ 0001 50 90 140”
50 PRINT 1 “ 0002 70 40 110”
60 PRINT 1 “ 0003 80 70 150”
70 CLOSE 1
80 OPEN “EXAMFILE.TXT” FOR OUTPUT AS 1
90 DO WHILE NOT EOF(1)
100 INPUT 1, test
110 PRINT test
120 LOOP
130 CLOSE 1
140 END
Note that Free-File function is used to determine the next available file handle to be used in the OPEN statement. However, in a bigger project that uses many files, Free-file ensures that there is no conflicting File Handles used. It‘s a good practice to use it whenever you‘re not sure of the number of files your program might need to open.
This is the line that does the physical opening of file and assigns it #FileNumber as its file handle. The ‘FOR INPUT’ part tells QuickBASIC that you want to open the file in Read mode as you‘ll be reading the contents of the file later in the example.
Next is the loop indicate by the DO WHILE NOT EOF (FileNumber) line. In QuickBASIC EOF () means End Of File. There is also BOF () for Beginning of File and LOF () for Length of File
Since you can’t go backwards on a sequential file, you won’t need BOF () at all.
DESCRIBE FILE INSECURITY
Computer file insecurity refers to the concept that a computer system is vulnerable to attack, and that this fact creates a constant battle between those looking to improve security, and those looking to circumvent security.
EFFECTS OF INSECURITY OF FILE
Data loss refers to the unforeseen loss of data or information. An occurrence of data loss can be called Data Loss Event and there are several possible root causes.
Overwriting is a process of writing a binary set of data on a memory. Overwriting generally occurs when unused file system clusters are written upon with new data. In simple terms, it writes over the previous data.
METHODS FOR FILES SECURITY
Backup or the process of backing up a file refers to making copies of files so that these additional copies may be used to restore the original after the data loss event.
Backup has two distinct purposes. The primary purpose is to recover data as a reaction to data loss, be it by data deletion or corrupted data. The secondary purpose of backups it is recover data from historical period of time within the constraints of a user-defined data retention policy.
An anti-virus program protects a computer file from malicious virus attack, detects and heals files that have been attacked.
It is a chosen secret string of characters that allows access to a computer, interface, files etc. The use of password is at user’s discretion and caution must be exercised by the user to remember the password always.
Differences between computer files and manual files
Manual is using old method without the help of the technology or maybe less to perform certain task or work while; computerized file system is using latest technology of ICT to carry out various tasks that is more effective when compared with manual system in terms of the productivity and time usage.
EVALUATION: 1. What are some basic operations that can be carried out on computer files?
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively