Syllabus Detail
- constants 11 ATAR, 12 ATAR
- local, global, parameters 12 ATAR
- naming conventions 11 ATAR, 12 GEN, 12 ATAR
- used in programming and also in pseudocode 11ATAR
Background
- Programming is all about writing the most efficient code to achieve a specific task
- By using variables and constants, we're able to store values temporarily
- These values can then be referenced or re-used to perform other tasks and functions
- Variables and constants are used in both programming and pseudocode
Variables
- A variable is a memory location that has its own associated name (known as an identifier)
- Variables are simply temporary stores that a program can access to reference or re-use a value during execution
- Unlike constants, variables can vary and have changing values
- Variables are used religiously throughout programming as they streamline efficienecy and allow for easier referencing
Constants
- A constant is another memory location that, like a variable, consists of an identifier and a value
- Unlike a variable, however, a constant does not change in value
- These are handy for fixed values such as the mathematical symbol Pi
- Pi is a constant is the value does not change
- Pi is given a symbol to represent the fixed value number, which is known as its identifier
Naming Conventions
- A naming convention is simply a set of rules put in place to ensure organization and consistency of variables and constants
- Many programming languages allow for a vast array of naming options for variables and constants
- How variables and constants are named in a program are often up to the discression of the developer(s)
- They're used to reduce the effort needed to read code as well as maintain consistency
- Some variables and constants have system or programming language restraints, such as words reserved for predefined functions
- It's generally sought after to name variables and constants with clear English words that relate to their use
Local Variables
- A local variable is a variable that is only accessible in the current code or module
- To write code you need to set up numbers and words that can be read by the program
- These numbers and words are given data types and values so they can be read.
- For calculating the area of a rectangle we need to be able to use the following variables
- length
- width
- total area
- To make length, width and total area, variables we need a data type and a value (VB example)
- Dim length As Double
- Dim width As Double
- Dim totalArea As Double
Global Variables
- The purpose of a global variable is to provide a variable that is accessible from anywhere within the program. eg so other functions or modules can use them.
- They are placed prior to other modules or functions.
- So, a global variable can be used in a module, only if it is in the code prior to that code.
- Ideally you want a variable to change, but as a global variable is used by different modules, it will cause confusion when it is changed.
- Global variables are not used much as they are limited in what they can do.
Parameters
- A parameter is a referenced variable or constant that is passed to a function or module
- We define a parameter of a function or module and tell the program what values are needed for it to operate
- These parameters can be passed into and out of a function or module
- They usually have brackets (parentheses) around them so are easy to find.
Further Research
- Check out ProgramWiz's article on C Variables and Constants here
- Check out Tuts+'s article on 9 Confusing Naming Conventions for Beginner's here
- Check out CodingUnit's article on Global and Local variables here
- Check out MSDN's article on Parameter Passing in C# here
Worksheet and Practice (yet to be added)
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