Information and Communication Technology (0417) | Design

ICT 0417: Study Notes – The Systems Life Cycle: Design (Section 7.2)

Welcome to the Design stage of the Systems Life Cycle! If Analysis was about figuring out the current problems and what the user needs, Design is where we create the detailed blueprint for the new system. Think of yourself as an architect drawing up plans for a new house—you need to specify every wall, door, and socket before construction can begin.

This chapter is vital because a poor design leads to an unusable system, regardless of how well it is coded later. Let’s make sure your designs are robust and effective!

1. Designing the Data Structure (File/Data Structures)

The first step in designing any ICT system, especially databases or spreadsheets, is deciding exactly how the data will be stored. This is called designing the file/data structure.

Key Elements of Data Structure Design

For every piece of information (field) you plan to store, you must define the following:

1. Field Name:
   

   The label given to the data.
   *Example:* Surname, Date_of_Birth, Product_Price.

2. Data Type:
   

   This defines what kind of data can be entered into the field.

   • Text (String): Used for letters, symbols, or numbers that won't be calculated (like phone numbers, postcodes, or names).
   • Numeric (Number): Used for values you want to calculate (e.g., marks, quantities).
     • Sub-types include: Integer (whole number), Decimal (number with fractional part), Currency.
   • Date/Time: Specifically formatted data for dates or times.
   • Boolean/Logical: Only accepts two values (True/False, Yes/No, 1/0, Checkbox). Used for simple choices.
3. Field Length:
   

   The maximum number of characters allowed in the field.
   *Example:* If a national identity number is always 12 characters long, you set the length to 12. This saves storage and helps prevent typing errors.

4. Coding of Data:
   

   Using short, pre-defined codes to represent longer pieces of information.
   *Example:* Instead of storing "Male" or "Female", you might code it as M for male and F for female. This saves storage space and ensures consistency (everyone uses the same spelling).
   

2. Designing the Input Formats

How will the user get data into the new system? The design must include input formats, often using data capture forms.

The goal is to make data entry fast, accurate, and easy for the person entering the data.

Design Requirements for Data Capture Forms

• Clear Layout: Group related fields together (e.g., all address details).
• Appropriate Spacing: Enough room for the user to enter data without confusion.
• Clear Instructions: Tell the user exactly what to enter (e.g., "Enter date in DD/MM/YYYY format").
• Use of Features: Use checkboxes (for Boolean data), radio buttons (for multiple choice single answer), or drop-down menus to minimise typing and increase accuracy.
• Validation Notes: If the input must follow specific rules (like a maximum length), these should be noted on the form design.

Imagine trying to fill out a tax form that has no labels and tiny boxes—it’s frustrating! A good input format prevents these errors.

3. Designing the Output Formats

Once the system has processed the data, it must present the results in a useful way. There are two main types of output formats you must design:

A. Screen Layouts (Soft Copy Output)

This is what the user sees on a monitor or mobile device. Good screen design focuses on ease of use (user interface).

• Clarity: Use clear fonts and colours that are easy on the eyes.
• Consistency: Buttons and navigation should be in the same place on every screen.
• Navigation: Use appropriate hyperlinks and menus to allow users to move easily between different parts of the system.
• Relevance: Only display the information the user needs for that specific task.

B. Report Layouts (Hard Copy Output)

This refers to information that is designed to be printed (like invoices, monthly summaries, or statistical reports).

• Professional Look: Includes logos, clear headings, and consistent margins.
• Pagination: Ensure page numbers, dates, and times are included, usually in the header or footer.
• Alignment: Numeric data should be right-aligned with currency symbols or percentages correctly formatted.
• Readability: Use columns and summaries so that printed data is easy to read and analyse.

4. Designing Validation Routines

Validation is the automated check performed by the computer as data is being entered to ensure it is reasonable and sensible. This is a crucial step in the design process to minimise data entry errors.

Validation does NOT check if the data is 100% correct (that’s verification), but if it falls within expected parameters.

Analogy: Validation is checking if your submitted school assignment is between 5 and 10 pages long (reasonable). Verification is checking if the actual content is the correct answer (correct).

You must design the system to include appropriate validation routines. Here are the types you need to know:

The Seven Types of Validation Checks

Memory Aid: Use the phrase: Really Curious Learners Try Finding Perfect Codes (RCLTFPC)

1. Range Check
   

   Checks if data falls within a specified minimum and maximum value.
   *Example:* If marks must be between 0 and 100, entering 105 or -5 would fail the check.

2. Character Check
   

   Checks that the data entered contains only the expected characters (e.g., only letters, or only numbers).
   *Example:* A field asking for a person's age (numeric) should fail if someone enters the word "twenty".

3. Length Check
   

   Checks that the data entered contains the correct number of characters.
   *Example:* A password must be at least 8 characters long (minimum check), or a phone number must be exactly 10 digits (exact check).

4. Type Check
   

   Ensures the data entered is of the correct data type defined in the structure.
   *Example:* If the field is designed to be a Date/Time type, entering a word like "Yesterday" will fail.

5. Format Check
   

   Checks that the data follows a specific pattern or structure.
   *Example:* A national identity number might be defined as two letters followed by six numbers (LL######). An email address must contain an '@' symbol and a '.' (dot).

6. Presence Check
   

   Ensures that a field has not been left empty. If the data is mandatory, the system must check for its presence.
   *Example:* You cannot submit an online order without providing a delivery address.

7. Check Digit
   

   Used primarily for identifying codes (like barcodes, ISBNs, or bank account numbers). The final digit of the code is calculated using an algorithm based on all the other digits. When the code is entered, the calculation is performed again. If the calculated digit doesn't match the entered check digit, the code is invalid.
   *Purpose:* This catches simple errors like transposing (swapping) two numbers during data entry.

Key Takeaway from the Design Phase

The Design phase converts the abstract needs identified during Analysis into concrete, detailed plans. These plans—covering data structure, input, output, and validation—are the instructions developers will use to build the system. A well-designed system is efficient, reduces errors, and is user-friendly.