Information processing

GOOD DAY, students. This is lesson 32 in our series of lessons. In this week’s lesson, we will begin to look at some of the key concepts of the unit called Information Processing.

METHODS OF VERIFICATION AND VALIDATION OF DATA

Before we examine the different methods of verification and validation of data, we need to examine some errors that may occur during the entry of data into a computer system or the sending of data.

TRANSMISSION ERRORS

This is when data received by a computer or system is not the same as what was sent by another computer, which could be as a result of an electrical fault or faulty cabling, as well as the computer used to send the data.

EXAMPLE

yyyyyoooo is transferred as x&*`^$yyoo

TYPOGRAPHICAL ERRORS

These are errors made typically by humans when we are typing data. This can also be said to be an accidental error (errors that are not made on purpose). For example, typing in a wrong date of birth.

EXAMPLE 2

I forgot my password to myi nstagram account. Typographical error

TRANSPOSITION ERRORS

These are errors made when numbers or characters are placed in the wrong order. An example of this could be when we are typing a date of birth for someone who was born on the 12th of September 1998 and we type 09/12/98 instead of the 12/09/98.

EXAMPLE 2

I swa Black Panther on Friday. It was epic! Transposition error

Some errors can also be considered to be deliberate, where errors are made by humans intentionally for personal gain or just to create disruption. For example, someone may falsify a document to gain acceptance in an institution or for a scholarship.

There are two ways of preventing errors made by humans and they are data verification and data validation. Data verification is a process carried out by humans, whereas data validation is an automatic process carried out by software.

DATA VERIFICATION

The errors we examined in the previous lesson would warrant the need for data verification. Data verification is the process of checking for errors that might have been entered in the computer from a source document or when data is copied from one medium or device to another. Two methods of data verification are double entry and proofreading/visual checks.

The double-entry method is the process of entering data more than once using a program that checks each second entry against the first. If the data entered is not the same, it will not get processed and the system will allow for the re-entry of data to ensure the data entered is accurate. An example of this process would be when you are required to enter your password twice when setting up your email to confirm your password.

Proofreading, on the other hand, checks the data entered against the data on the original source document. This method can be time-consuming, as it requires the user to read the information from the source document and check it against what was entered in the system.

Visual checks utilise on-screen prompts. When a set of data is entered, it is redisplayed on the screen. The user is prompted to read it and give a confirmation that the data entered is correct. If the data is incorrect, the data is re-entered.

DATA VALIDATION

Data validation employs several ways of checking for the accuracy and completeness of data. Let us examine the most popular methods that can be used to validate data.

RANGE CHECKS

Range check ensures that the data entered is within a particular range. Examples of such a check would be data pertaining to the number corresponding to the months of a year and not exceeding the number of hours in a day.

REASONABLENESS CHECKS

Reasonableness checks ensure that data is reasonable; that is, the data entered is realistic. For example, a student enrolled in first form with a particular date of birth; his or her age, when calculated by the computer system, should correspond (say age 11). Thus, a child who is 17 years

cannot be linked to a date of birth younger.

DATA-TYPE CHECKS

Data type checks, also called character checks, ensure that the right type of data has been entered. They ensure that if you intend to enter numbers, only numbers are allowed to be entered, and if only characters or symbols are intended to be entered, then only that type of data is allowed. Example, if you are storing someone’s name, only letters would be entered; values would not be allowed.

INCONSISTENCY CHECKS

Consistency/inconsistency checks compare data you have entered against other data you have entered. If you enter a person’s year of birth and age in separate fields, a consistency check will ensure that the two fields correspond with each other. Thus, if the age of an individual is not in line with his/her date of birth, then this would be considered to be inconsistent.

PRESENCE CHECKS

This check ensures that required data is always present. For example, if in a database information is stored on a set of employees and each employee must have an ID number, a presence check will ensure that the ID field is not left blank. On the other hand, there are cases where some fields in a database may be optional. For example, not everybody may have a house number but everybody may have a cell phone, so the field which stores a customer house number may be left blank.

FILE ORGANISATION AND ACCESS

File organisation and access relate to the use of records, fields and files stored in a database. You would have been exposed to all three terms when you did the productivity tool: database in class.

A file has three important characteristics and they are as follows:

A file can either be permanent or temporary.

The manner in which the records of the file are organised on a secondary storage device (file organisation).

The manner in which records are accessed.

There are two main types of files that businesses and organisations utilise: they are a master file and transaction file.

A master file is a permanent file which is kept up to date and stores the main information, summary data and key fields in the data. The master file contains two types of data: data that is permanent, such as an employee’s personal data, and data that is less permanent, which is updated on a regular basis, such as the hours worked by an employee.

A transaction file is a temporary file which is used to update the master file after a certain time, whether weekly or daily. A transaction file adds a new record, updates, and deletes records of a master file. See a diagram illustrating this process below (figure 1).

There is also another file, known as a transaction log, which keeps a record of changes to the transaction file. This will keep a record of the history of what transactions have taken place and not just the recent one.

SEQUENTIAL FILE ORDERING

This is where records are stored in a logical or sorted order. Records can be arranged according to name, date, size or any other field in ascending order.

10 20 30 40 50

SERIAL FILE ORDERING

This is similar to sequential file ordering, except the records are not stored in any particular order (unordered). They are simply stored one after the other as they are added, similar to new items on a shopping list, where as you go along you add what you need. This type of ordering is often used to capture transactions as they occur during the day.

50 20 44 60 15

Sequential access means that records are accessed one by one in the order they are stored until the right one is located. Serial access is similar, as you can access the records in the same manner in which they were stored.

RANDOM FILE/DIRECT ORDERING

Files are stored in any order using a key. The file is organised like a one-dimensional array, where each array element has an index/subscript to mark its location. Random access or direct access allows you to access the record you want without having to go through any others, unlike sequential access. The computer locates the data item using the indices.

INDEX SEQUENTIAL FILE ORDERING AND ACCESS

Index sequential file ordering uses an indexed file to store records similar to an index in a textbook. Records are stored in this file in sequential order and a set of indices is used to refer to each item stored in the file. Each record can be accessed by its index number. Thus, this file ordering is a combination of sequential and direct file ordering and is utilised when records need to be sorted sequentially but individual records must be accessed quickly. See diagram below.

By using both methods (sequential and direct), the following can be done: you can go through each record sequentially (one after each other) and you can access a specific file directly (there is no need to go through any previous data (random)).

This lesson brings us to the last in our series of IT lessons for CSEC. On this note, I would like to remind you to practise as many past-paper questions as possible, which will allow you to have an idea of the manner in which you will be tested, how the questions will be structured, and key areas you will likely be tested on. In addition, follow the pointers given by your teacher and ensure you take adequate rest prior to your exams. I would also like to share this message with you from messages .365 greetings. com Remember, if you fail to prepare, you prepare to fail.