5. Writing maintainable programs

5. Writing maintainable programs

1. define terms

   • variable- a value that can change while the program running
   • constant- a value that cannot change when the program is running
   • identifier- a name given to controls, variables...
   • reserved words/ keyword- words that are specified by the program to tell it to do a function, e.g. If, Else, Char

2. good program-writing techniques

   • suitable identifiers
     • easy to understand
     • less errors- can trace variables- can spot them
     • sensible name: Hungarian Notation- txtScore, Camel case- uses capital letters or underscores- there are no spaces
   • subroutines
     • breaks the program- easier to make
     • general advantages of a subroutine...
   • indentation
     • standard techniques mean that everyone can understand it
     • indent at the start and end of each code structure
     • easier and clear to understand
     • know where each structure starts and ends
   • comments
     • need to understand it in the future or if someone else looks at it
     • easy to maintain
     • easy to find and correct errors
     • Header comment- at beginning- contains name, what program does, programmers name, date, errors
     • Subroutines need a comment- explain what it does, how it will be called, parameter needed
     • explain purpose of variables and constants and explain lines of codes (come before the code)
   • formating- code should be grouped in logical blocks- have blank lines between them

3. modularised programs

   • look back at 3.2.1
   • each module is made into a subroutine; this means that different programer can work on the same program

4. declare variables and constants

   • how to declare variables and then afterwards
     • data type
     • a suitable name- use descriptive names so that it is easy to understand, no spaces (uses underscores), don't use reserved words
     • scope
       • local variable- used only in the subroutine it is declared
       • global variable- can be used anywhere in the program
     • initialise after declaring, restarts variables when program starts again, number-0, bool-False, string -""
   • why declare them?
     • translator can save memory for them
     • translator does not think it is a reserved word
   • Conventions for naming
     • used to show data type or enhance readability
     • These can be: sentence case, camel case, including type of variable (intAge), include local variable or not, Hungarian notion
   • constants
     • data that stays the same throughout the program
     • need to declare it because it needs to be understood by everyone, the actual data might have no meaning to someone else, e.g. gravity is easy to understand unlike 9.81