ICT2 - Information: Management and Manipulation
Topic 1: Introduction to Computer Systems
Topic 3: Verification and Validation
Topic 4: Introduction to Databases
Topic 1: Introduction to Computer Systems
See the Complete, Illustrated Guide to PC Hardware (external link)
You should be able to draw a block diagram of a computer system showing Input, Output, Processing and Feedback.
Feedback is output that is returned to appropriate members of an organisation to help them refine or correct the input. Feedback, therefore, forms a loop in the block diagram.
You should have notes on the following:
Step by Step Guide to Buying a PC
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See the Complete, Illustrated Guide to PC Hardware (external link)
You should have notes on the following:
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Topic 3: Verification and Validation
You should have notes on the following:
PowerPoint Presentation on Data Validation
It is important to understand the difference between "verification" and "validation".
Verification checks check to see if something is actually true. Validation just checks to see that data is valid.
If I entered my date of birth as 30/2/66, that would be an invalid date because February doesn't have 30 days.
If I entered my date of birth as 28/2/66, this would be a completely valid date of birth. However, it is not my real date of birth. If someone tried to VERIFY my date of birth, they would find that this date is false.
Therefore, data can be VALID but INACCURATE.
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Topic 4: Introduction to Databases
About Databases - read about databases and their advantages
Basic Introduction to Databases
Getting Started with Databases using Access
1. What is a Database?
The traditional database is a filing cabinet. What advantages do databases have over filing cabinets.
2. Flat File v Relational
The traditional system is for each department in an organisation (e.g. sales, marketing, personnel) to have their own flat file database. A flat file database is one which has only one table. Flat file databases are simple, stable and fast. You can even use a spreadsheet program as a flat file database.
The RDMS (Relational Database Management System) is for the whole organisation to use one relational database. A relational database is one that has many different tables that are linked together through a system of "relationships" between fields in different tables.
The disadvantages are:
The advantages are:
3. Types of Relationships
4. Normalisation
Powerpoint Presentation on Normalisation
This is the process of structuring your database in the most efficient manner possible. The principles of normalisation are:
5. How to Avoid Many to Many Relationships
Use the example above. A hotel has many guests. Many different guests will use the same hotel room (not necessarily on the same night!) The same guest may return to the hotel and book a different room. Therefore, it is easy to assume that you have to have a Guests table and a Room table with a many to many relationship between them because many guests are booking many different rooms.
However, if you add a bookings table you can turn your many to many relationship into a one to many relationship plus a many to one relationship. One customer can make many bookings and one room can be booked many times.
6. Queries
Why do we use electronic databases instead of the traditional method of filing information (i.e. filing cabinets)? One of the main advantages of databases is that they can easily be searched, sorted and filtered. It is a laborious process to search through filing cabinets. Sorting and filtering would take even longer. If you wanted to search or sort information from several different filing cabinets, the job would quickly become a mammoth operation. However, with a powerful relational database, the job is very easy, very quick and very accurate.
You should be familiar with the following different types of query:
(i) Sorting - this involves putting information into a sensible order. Sometimes you want to sort your records A-Z according to surname. Sometimes, you want them in order of membership number. Sometimes you want to list them in order of income. You can sort any way you like in Access.
You can sort any field of any table just by clicking the Sort Ascending or the Sort Descending buttons. You can also sort as part of a query or filter.
(ii) Filtering - Filters remove records from your table to show you only the records that you want to see. They don't actually delete any records, they just hide them from view until you remove the filter. For example, you might want to filter your artists table to show only the artists who are American, or you can show a list of club members over the age of 60 or below the age of 18, or you can have a list of only female members or a list of members who live in a particular town.
There are three filtering tools in Access. Which one you use will depend on the complexity of the filter you want to perform.
(iii) Select Queries - This is the simplest type of query. A select query is a basic search - you are selecting information that you want to see. You can combine fields from several tables in a query.
You need to understand the nature of Boolean Operators to really search effectively.
You can get queries to perform calculations such as SUM, AVG and you can get other statistical information, such as COUNT, MIN and MAX. These functions might be familiar from using spreadsheets.
You can create calculated fields to do a calculation on one or more numerical fields. Calculated fields are ideal for answering "What if . . .?" questions, such as "What would be our new pricelist if we increased all our prices by 5%?"
You can use the Simple Query Wizard or you can construct the query yourself from the Design View.
(iv) Action Queries - This type of query performs an action on your database (i.e. it changes the design and/or the content of your tables). Therefore, it is a very good idea not to run the query until you have previewed the results. There are six types of action query that you should be familiar with.
Examples: If you want to delete just one record, simply open the table and make the change. If, for example, you want to delete all your French customers, you could use a Delete Query to make the job quicker and to make sure you get rid of every unwanted record.
If British Telecom change the dialling code for a town, you could use the Update Query to correct all the affected phone numbers at once.
(vi) Crosstab Queries - Crosstab queries are used to summarise data in tables. It has a rows and columns format - you can think of each row as a record and each column as a field (just like a table). In addition, the crosstab query performs calculations.
7. Reports
Reports are important because people often want a "hard copy" of certain information in the database. For example,
If you are preparing a mailing to your customers, you can use a report to print the address labels.
A library could produce a list of borrowers who have overdue books
A business might want a report of sales figures for a certain period
A products catalogue could be produced
Reports can be used to produce invoices
There are several report wizards. Which one you use depends on the complexity of the report you want.
Reports can include graphs and they can also perform calculations.
You can base a report on any table or query or any combination of these.
Reports can be customised and formatted to give a professional appearance.
8. Forms
You can enter data straight into tables if you like but a form is usually better for your average data entry clerk because:
Forms present a more attractive appearance for the user
The fields can be placed in a convenient order
Some fields can be given a default value
Validation can be performed automatically on certain fields
A form can be used to enter data into several tables at once
Different forms can be available to different users
Certain controls can be hidden from forms
Forms allow the user to focus on one record at a time
Forms can be redesigned at any time (compare with PBF)
Entering data directly into a computer reduces the risk of error
Forms can be built from scratch or you can use a selection of wizards.
Forms can be customised and formatted to give a professional appearance.
A Switchboard Form can be used to give the user a pleasant interface when the database starts.
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