Understanding Functions: The Building Blocks of Code

Writing Functions

The Big Idea • What if this was how we did powers?

Information • Functionheader specifies everything but job of function • A contract to do work

Review • A functiondeclaration : • Prototype • Statements that do work of the function

A Function • A function: -Called max -Takes two inputs (ints) -Gives back an int

Using Max • Using Max:

Full Program • Must declare afunction beforeit is used

Function Name • Function name • Normal identifier rules • no spaces, can't start with number, etc… • Use camelCase • Clearly identify job • Readability > terseness • Focus on verbs

Body • Body of a function – where magic happens • Always a block of code { } • Has own scope • Variables declared inside only available inside

Parameters • Parameters : information function needs • Declare with: type name, type name, type name… • OK to have no parametersintgetHourOfDay()…

Parameters • Parameters are special variables • Only exist within this function • Initialized with value caller passes in:abs(10)  number = 10

Function type • returnstatement used to pass answer back • Must return right type of data

Function type • returnstatement used to pass answer back • OK to have more than one return • Every path must return

Void Functions • Void : nothing • Void function type returns nothing • Just does some work • Returns at }

Call Stacks • Each function works in a separate stack frame in memory

Rules For Functions • Only variable available are: • Parameters • New variables you declare in function

Rules For Functions • Do NOT use cin/cout

Rules For Functions • Do NOT use cin/cout • Unless job of function is to print or get input

Comparison Return a grade: Print a grade:

Understanding Functions: The Building Blocks of Code