CS145: Functions and Scope

• What is a function?: A named and self-contained piece of code that may be executed (i.e. called) many times.

• Why use functions?

  • Modularity: No functions (txt) vs functions
  • Readability
  • Re-usability

• Syntax:

  reurnType functionName(arguments) {
  	// code body
  }
  

  For now, we will have a "void" return type and no arguments:

  void functionName() {
  	// code body
  }
  

• What is the difference between defining vs calling (i.e. executing) a function.

• What is the order of execution?

  • Some functions have special meanings and do not need to be explicitly called: setup() and draw()
  • User defined functions need to be called explicitly.

• Scope: Where is a variable recognized? Depends on where it is declared. Look at colored regions of these programs:

  • No functions used: all variables are global
  • Example 1 - with functions: no variables are global
  • Example 2 - with functions: one variable is global (txt)
  • Some functions have special meanings: setup() and draw()