Producing Robust Programs

Producing Robust Programs

1. Validation

   • Validation ensures that any data input is possible and sensible.
     • A programmer can build various types of validation into a program:
       • Range check - the input must fall within a specified range when making a payment to someone, the amount to be entered might be set to be greater than zero and not greater than the funds available.
       • Length check - the input must not be too long or too short. For example, a surname will require at least one letter, but is unlikely to require more than 40.
       • Presence check - a data value must be entered. For example, entering a quantity when placing an order.
       • Format check - the data must be in the correct format, such as entering a date in the format DD/MM/YYYY.
       • Type check - the data must be of a specified data type, such as an integer when specifying a quantity.

2. Data Sanitisation

   • Authentication is the process of a user confirming that they are who they say they are on a computer system.
     • The factors of authentication can be broken down into three main groups:
       • something you are - username, bank account number, or anything that identifies the user uniquely
       • something you know - password, pin, secret answer to a question
       • something you have - swipe card, biometrics, any other physical identifying device

3. Maintainability

   • The purpose of maintainability is to ensure that, over time, a program can be easily maintained.
     • Indentation: Code within selections or iterations should be indented. This allows the programmer to easily see which code falls within the selection or iteration, and where it ends.
     • Sensible variable names: Many programmers choose meaningless variable names such as x or y. While a program will run with such names, it makes understanding the purpose of the variable much more difficult.
     • Comments: Comments are lines in programs that provide information about what the different parts of the program do.

4. Authentication

   • Authentication is the process of a user confirming that they are who they say they are on a computer system.
     • The factors of authentication can be broken down into three main groups:
       • something you are - username, bank account number, or anything that identifies the user uniquely
       • something you know - password, pin, secret answer to a question
       • something you have - swipe card, biometrics, any other physical identifying device