Data entry

After studying this section you should be able to

• distinguish between data and information
• describe the various sources of data
• select appropriate methods of data entry
• explain how errors in the data can be detected and corrected

Data and data gathering

Data consist of facts and figures that can be obtained from various sources. The purpose of an information processing system is to take in data and turn them into something useful that we call information. An example might be the national census. The data consist of millions of facts and figures about the population that have been recorded on paper and the information we need is how many people live in the different towns. The information system will calculate the totals and output them. Data can come either directly from the source or indirectly from other information systems, so the information from one system may be data for another.

A simple way to think of the difference between data and information is that a system will normally process data to produce information

Data may be gathered either manually or mechanically. Some of the common methods are:

• Keyboard entry – often from handwritten forms
• Optical character recognition – usually typed but can be handwritten
• Optical mark recognition – useful when the options are limited
• Barcodes – used on consumer products
• Data logging by other computers – such as palmtop devices
• Voice entry – security devices but may be more common in future
• Image capture by scanner or camera – useful when pictures are required.

There are other methods of data entry but these are the most common. The important point is to match the data entry method to the application.

KEY POINT - You need to select appropriate data entry methods for the application.

Data validation

There are a number of checks that can be carried out to ensure that data are correct when they enter the system. Always consider what information is available to the system at the point of data entry before suggesting a validation method.

The examiner will be expecting you to show that you can select an appropriate method for the data being validated.

Character - Each fact or figure is normally called a field and the format of a field can be checked in various ways. If the field should contain a number it cannot have any alphabetic characters. In the same way a field containing a name cannot have numerical characters.

Format - Some fields have quite complex formats where numbers have to be in some places and characters in others, for example National Insurance code, postcode.

Length - Most fields have a maximum length and some have a minimum length.

Range - This normally applies to numerical fields. There may be an acceptable range of values.

Verification - This check can be applied when there is some means of comparing the data after entry with the correct version. Ideally the correct version is in the system on a file or database but this is often not available. In this case some systems will insist on the data being entered again to ensure they are correct (you may have been asked to do this with a password). A less efficient means of validating data is to ask the operator ‘is this correct?’ after all the data have been entered.

An automatic means of data verification is to add an extra digit (known as a check digit) to a field. This is normally applied to a code which is given by the computer, for example a bank account number, a stock code, etc. The computer calculates the check digit when the number is supplied. Every time the code is entered into the system the code is checked to ensure that the data are correct.

Control total -

The supplier of the data is asked to total up some numerical field and enter this total with the rest of the data. This value can then be checked to ensure that the data covered by the total are correct. This control total may well be a useful total for manual processing as well: for example, the total number of packages in an order, the total value of an order.

Hash total - A hash total serves the same purpose as a control total only the total has no useful value except for checking purposes. An example might be to add up all the stock codes on an order.

Batch total

Often data are prepared off-line and transmitted to the system in batches. In this case batch totals may be used. A batch total applies to the whole batch, for example the total number of items in a batch.

KEY POINT - It is vital that you apply an appropriate validation check to data. Do not assume that you have access to the files or database unless the question tells you that this is the case.