Design, Testing and IDEs

advantages of structure diagrams (5)

• coding is easier

• easy collaboration because modules are written independently

• easy to test each module individually

• easy to fix each module

• reuse the subprograms

why should code be well maintained?

• easier for other programmers to understand

how to improve maintainability of code: (4)

• comments - explains code to other programmers

• indentation - programmers can see the different structures

• naming conventions - programmers can understand the purpose of the variables and keep track of them

• subprograms - programmers see how different parts work

how can programmers protect their programs with defensive design? (3)

• anticipate misuse and prevent it

• ensure their code is well maintained

• reduce the errors with testing

define input validation

checking if data meets certain criteria before passing it into the program

5 input validation checks:

• range check - within specified range

• length check - correct length

• format check - correct format

• presence check - entered data

• look-up table - against acceptable values

how to increase the security of a password based authentication system: (3)

• strong passwords changed regularly

• limit failed attempts

• random selection of characters from the password

define syntax error

problem with the grammatical rules of the programming language. code doesn’t run

define logic error

problem with the code which still runs but produces an unexpected output

what is iterative testing?

program is tested during development. modules are tested so that they work

what is final testing?

testing the whole program at once after it has been developed

4 types of test data:

• boundary - limit of the range

• erroneous - incorrect data type

• normal - correct and should be accepted

• invalid - correct data type, outside of range

characteristics of high level languages: (5)

• one line represents many of machine code

• code works on different processors

• code is easy to read, write, teach and understand

• must be translated

• programs are slower and less memory efficient

characteristics of low level languages: (4)

• compatible for one processor

• code is hard to read, write, teach and understand

• doesn’t need to be translated

• more memory efficient and faster

define interpreter

translates code line by line

define compiler

translates the whole code and produces an executable file

advantages of interpreter: (2)

• better for debugging because the code stops once an error is found

• less memory use

disadvantages of interpreter: (2)

• programs run slower - translated every time

• has to be distributed with source code (no executable file) - modified without permission

advantages of compiler: (5)

• run quickly once translated

• creates executable file - cannot be modified

• only needed once

• optimises code

• produces an error report of all the errors

disadvantages of compiler: (3)

• worse for debugging - errors returned after all the code has been translated

• compiling is slow

• memory use

features of IDEs:

• code editor

• run-time environment

• error diagnostics

• translators

• (Breakpoints)

what does a code editor have?

• line numbering

• auto-colour coding

• auto-correct

• auto-indentation

• auto-complete

how do error diagnostics help?

• debugging to find errors

• location of the error and how to fix it