$//$Lab$10-1.$cpp $-$ circle calculations

$//$Created$/$revised by on

#include

#include

using namespace std;

$//$function prototypes

void displayChoices$()$;

void getArea$($double rad, double &area$)$;

void getDiameter$($double rad, double &diameter$)$;

int main$()$

$\{$

int choice $=0$;

double radius $=0\mathrm{.}0$;

double circleArea $=0\mathrm{.}0$;

double circleDiameter $=0\mathrm{.}0$;

displayChoices$()$;

cout $<<$ "Enter your choice $(1$ or $2)$: $"$;

cin $>>$ choice;

if $($choice $<1||$ choice $>2)$

cout $<<$ "Invalid choice" $<<$ endl;

else

$\{$

cout $<<$ "Radius: $"$;

cin $>>$ radius;

if $($choice $==1)$

$\{$

getArea$($radius$,$ circleArea$)$;

cout $<<$ "Area: $"<<$ circleArea;

$\}$

else

$\{$

getDiameter$($radius$,$ circleDiameter$)$;

cout $<<$ "Diameter: $"<<$ circleDiameter;

$\}//$end if

cout $<<$ endl;

$\}//$end if

return $0$;

$\}//$end of main function

$//*****$function definitions$*****$

void displayChoices$()$

$\{$

cout $<<"1$ Circle area" $<<$ endl;

cout $<<"2$ Circle diameter" $<<$ endl;

$\}//$end displayChoices

void getArea$($double rad, double &area$)$

$\{$

const double PI $=3\mathrm{.}141593$;

area $=$ PI $*$ pow$($rad$,2)$;

$\}//$end getArea function

void getDiameter$($double rad, double &diameter$)$

$\{$

diameter $=2*$ rad;

$\}//$end getDiameter function

QUeStIoNS$1.$ The main function passes two variables to the getArea function. Which lines in the program indicate whether the variables are passed by value or by reference?

$2.$ Why is the radius variable passed by value? Why are the circleArea and circleDiameter variables passed by reference?

$3.$ Why is the displayChoices function a void function?

$4.$ How do the getArea and getDiameter functions, which are void functions, send information back to the main function?