Entering Data

After completing this section you should be able to:

• explain why data may be entered into an information system in code form
• list points to remember when designing codes
• explain the structures for organising data that is stored in an information system

Encoding data / Information

Data is often entered into an information system in code form. There may be a number of reasons for this, such as:

• codes can be typed in more quickly, and make subsequent searches faster too
• using codes reduces the size of files, so that data processing is faster
• codes are often unique. For example, each product in a supermarket will have a unique code. If a search were carried out without a code, and a more general term such as ‘corn flakes’ were keyed in to start the search, it would locate more items than keying in the code that would find the specific type of corn flakes required

KEY POINT

There are certain important points to remember when designing codes:

• They must be easy to use. If operators find codes impossible to remember, or long and awkward, they will not want to use them.
• Codes should always be the same length. This then provides an easy way of performing a validation check on them (see checking data on input section). If the code is too long or too short, it is obvious that a mistake has been made.
• Codes must not be too short. Although short codes are easier to enter, there is more likelihood of running out of codes, and, where security is an important issue, short codes are easier to break and copy.

Data / Information structures and storage of data

Huge quantities of data are entered into the average information system. It is vital that the data stored in that system is organised in a methodical way so that it is accessible. All data is stored in files, which have to have file names.

• You will be expected to understand the terms files, data, fields and records.
• You should also understand why each is important.

Within each file, data is divided into records. A record may contain just one piece of data. In this case it is said to have a single field. It may, on the other hand, contain many pieces of related data items, in many fields.

For example, a company may store information about each employee in a single record. Each record will consist of a number of fields, one for the name of the employee, one for the National Insurance number, one for the street address, and so on.

A field holds just one piece of data. For example, in an address list, the postcode part of the address might be stored in one field containing the right number of characters for the postcode.

The term field also refers to a place where information is entered on a screen. For example, a cell in a spreadsheet where a product price is to be entered is a field.

Key Field

This is a term used to describe a field that is unique to a particular record and that can therefore be used to search a file to locate the record quickly. For example, each employee in a large company may be given a unique employee number. Using the number as the key field, the employee’s record can easily be found in the company’s information system.

A key field must be  unique. No two people can have the same reference.

Text files – numbers and / or letters

A text file is a file that contains lines of written information that can be sent direct to a screen or printer by using ordinary operating system commands.

The files produced by word processors are normally not text files. Although they contain text, they also contain special codes that are not usually displayed on the screen but govern important formatting functions such as margins, underlining, and so on. The meaning of these codes is special to the word processing software being used. Most word processors can, however, produce text files and provide an option for this under the File Save As menu.

You will not be expected to remember different types of files, for example .doc used by Microsoft Word. You should understand that different types of software save files with different file extensions.

KEY POINT

A simple text file made of numbers and or letters consists of the code for each character in the file. The ASCII character code is normally used. It does not contain any special command or formatting codes, but end of line markers do have their own ASCII code, so they are included. Files are often converted into simple ASCII code when they are to be transferred from one information system to another because most software packages are able to read ASCII code.

QUESTIONS

Question 1

Why is code sometimes used to enter data into an information system?

Answer

Code may be used for one, or a combination of, three main reasons. Codes can be input more quickly, and make searches faster too. Using codes reduces the size of files, so that data processing is faster.

Question 2

What are the important points to remember if you are designing a code?

Answer

A code must be easy to use. It should be easy to remember, and not too long or complicated. Codes must not be too short either and should always be the same length. This provides an easy way of performing a validation check on them.

Question 3

What is a key field?

Answer

The term used to describe a field that is unique to a particular record and that can therefore be used to search a file to locate the record quickly.