Using the list of requirements, the systems analyst now has to design the new system.

In most cases the new system will be computer-based. The ease with which computers can communicate and process data means that are usually the best tool for the job.


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Designing the System Inputs

To get data into a system is a two-part process:
  1. Data must first be ‘captured’ (collected in a way that then makes it easy to input)
  2. Data must be input into the computer
The systems analyst will select a data capture method and data input method that best suit the requirements of the new system.
Sometimes the two steps of data capture and data input are performed at the same time.

For example a barcode reader captures the data (the numeric code on the barcode) and inputs it to a computer in one go.
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Choosing the Best Data Capture and Data Input Methods for the System

Collecting data into a form that is ready for input to a computer system can be done in many ways...
Paper Forms
Form can be a simple ones with spaces for numbers and text to be written in. The data from this form would then be typed into the computer

Forms can also be machine-readable, such as OMR forms
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Barcode Reader
Barcode readers capture the numeric code that the barcode represents.

Typically used with POS systems and also stock-control systems
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Card Reader
Many cards contain data stored on a magnetic strip or in a small bit of memory (smart cards) which can be captured with a card reader

Used in systems such as EFTPOS
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Capture still or moving images which can then be input to a computer for processing
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In the payroll example, the hours worked by the employees could be captured using...
  • A paper form (a timesheet) - simple and cheap, but the needs to be manually input (slow) and the form can be lost
  • Barcode reader - employees could have ID cards and swipe them at the start and end of work (can cheat easily)
  • Fingerprint reader - employees could put a finger on the reader at the start and end of work (hard to cheat)
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Designing On-Screen Forms for Data Input

Much of the data that enters computer systems needs to typed in. A well-designed on-screen form can make this task easier and quicker.

On-screen forms should...
  • Have all of the necessary fields
  • Have obvious places for user input (boxes, use of colour, etc.)
  • Use appropriate controls (see below) for each field
  • Have text box controls that are the right size for the data
  • Have easy-to-understand instructions (if needed)
  • Make good use of the screen area available

Form Controls

On-screen forms can have a variety of controls (the little buttons / boxes that you click or type in):
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Used for normal text input
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Used to perform an action
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Option / Radio Buttons
Used to select an option (only one can be picked)
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Tick / Check Boxes
Used to select options (more than one can be ticked)
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Drop-Down Menus
Used to select options from a list

As data is entered into the form, it needs to be checked for accuracy. Two techniques help us do this: validation and verification...
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Above is an example of a well-designed on-screen form.

Note the clear instructions, labels and layout.

Note that appropriate controls have been used for each field

Data Validation Techniques

When data is input to a computer, it is a good idea for the computer to check that the data is sensible (no dates of birth in the future, etc.)

Checks like this are called validation checks (is the data valid?)

Different validation checks can be used on different fields, depending on the type of data being entered...

Presence Check
Is data actually present in a field, or has it been missed out?
Range Check
Is the data value within a set range?
(E.g. an exam mark should be between 0% and 100%, a month should be between 1 and 12)
Length Check
Is an item of text too short or too long?
Type Check
Is the data the correct type?
(E.g. the letter ‘A’ should not be allowed in a numeric field)
Format Check
Is the data in the correct format?
(E.g. a date of birth should be entered as dd/mm/yyyy)
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If one of the validation checks fails (because the data entered is invalid) the computer should show a nice, friendly error message such as...

“You have forgotten to enter a name”

Data Verification Techniques

Data validation only checks whether the data entered is sensible - it does not mean that the data is the right data.

For example, if you are entering a date of birth and you mis-type it…
  • Correct date of birth: 12/11/1982
  • Date of birth entered: 12/11/1928
. . . you would not see an error, since 12/11/1928 is a valid date of birth.

To check that data is the correct value, we use a system called data verification.

There are two methods of data verification...
Proof Reading
After the data has been entered a person compares the original data with the data in the computer (either on the screen or using a print-out).

If mistakes are spotted they can be corrected by the person.

Proof-reading is quick and simple, but doesn’t catch every mistake.
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The data is entered into the computer twice (preferably by two different people).

The computer compares the two sets of data to see if they match. If not it generates an error and a person will need to correct the mistake.

Double-entry takes more time and effort, but it catches almost every mistake.
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A common example of double-entry verification is when you are asked to choose a new password - you are usually asked to type it in twice to make sure you've typed it correctly (since the actual letters are hidden)

Designing the System Processes

Any system has to process the data it is given. The system designer has a number of things to consider...

Designing Data and File Structures

A data structure is an organised collection of data. Most commonly, this will be some sort of database in which data will be stored as it is being processed.

When designing a database, the system designer needs to consider:
  • The type of data being stored (numbers, text, dates, etc.)
  • The size of the data (how long is a typical name, etc.)
  • The field names to use
  • How many records will need to be stored
(see the Data Types section for more details about these)

The designer also need to consider which backing storage device and media will be suitable to store the data:
  • How often will the data need to be accessed
  • How quickly the data needs to be accessed
  • How large will the data files be
So, for example, if there is a large amount of data that needs to be accessed quickly, and regularly, then a hard drive would be the best storage device to use.
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Designing the How the Data Will be Processed

Of course, the system designer also needs to design the actual steps to be followed to processing the data (the algorithm).

(This part of the design is outside of the scope of the IGCSE syllabus, but I've mentioned it for completeness)

You don't need to know how to write algorithms for IGCSE!
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Designing the System Outputs

There are usually two types of output from a system that need to be designed:
  • On-screen reports (information displayed on the monitor)
  • Printed reports (hard-copy to be mailed, filed, etc.)

Designing On-Screen Reports

Designing an on-screen report is similar to designing an on-screen form (see above). There are a number of things that the designer should consider.

On-screen reports should...
  • Show all of the necessary fields
  • Have fields that are the right size for the data
  • Have easy-to-understand instructions (if needed)
  • Make good use of the screen area available
  • Make good use of colours and fonts to make the data clear
This is an example of a well-designed on-screen report used to show details of an employee…
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On-screen reports can include more than just text...

Reports can include:
  • Text
  • Images
  • Bar charts
  • Pie charts
  • Animations
  • Video

Designing Printed Reports

Designing a printed report is just like designing an on-screen report (see above), except that the report needs to fit a piece of printer paper, rather than the screen. The report might also include page numbers, a header / footer, etc

This is an example of a well-designed printed report used to show details of an employee…
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Printed reports often have features that on-screen reports don't have, such as page headers and footers (containing page numbers, etc.)

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