Component 02 - Design, Testing and IDEs

Component 02 - Design, Testing and IDEs

1. Translators

   • Compiler
     • Translates all of the source code at the same time and creates one executable file
     • Only needed once to create executable file
     • Returns a list of errors for the entire program once compiling is complete
     • Once compiled the programruns quickly, but compiling can take a long time
   • Interpreter
     • Translates and runs the source code one instruction at a time, but doesn't create an executable file
     • Needed every time you want to run the program
     • The interpreter will return the first error it finds and then stop - this is useful for debugging
     • Programs will run more slowly because the code is being translated as the program is running

2. Testing

   • Syntax error
     • when the compiler or interpreter doesn't understand something you've typed because it doesn't follow the rules or grammar of the programming language
   • Logic error
     • when the compiler or interpreter is able to run the program, but the program does something unexpected
   • performance test
     • Tests how quickly certain features run and their impact on computer resources
   • Usability test
     • Tests how user-friendly the interface and features are
   • Security test
     • Tests vulnerability to attacks and how securely data is stored
   • Load/Stress test
     • Tests how it copes under extreme conditions, e.g. lots of users at the same time
   • Final testing
     • the program only goes through the development cycle one. All the required features of the program are added at the same time. The program is tested against the initial requirements of the customer
   • Iterative testing
     • the program will goes through the development cycle a few times. The idea is to try and get the program to match what the customer really wants. The requirements in the first cycle might only include the main features of the program. At the start of each new cycle the requirements will be adjusted
   • Normal data
     • things that a user is likely to input into the program
   • Extreme (boundary) data
     • values at the limit of what the program should be able to handle
   • Erroneous data
     • inputs that the program should not accept

3. Defensive Design

   • Input sanitisation
     • Removing an unwanted characters before passing data through the program
   • Input validation
     • Checking if data meets certain criteria before passing it into the program
   • Range check
     • Checks the data is within a specified range
   • Presence check
     • Checks the data has actually been entered
   • Check digit
     • Checks the numerical data has been entered accurately
   • Format check
     • Checks the data has the correct format (e.g. date)
   • Look-up table
     • Checks the data against a table of acceptable values
   • Length check
     • Checks the data is the correct length