//  loop example 0: Numbers

#include <iostream.h>

void main()
{
int i;
i=1;
while(i<=10)
 {
  cout<<i<<endl;
  i=i+1;
 }//end of while loop
cout<<"That's All Folks! "<<endl;
}// end of program




//------------------------------------------



// loop example 1: trianglular numbers

#include <iostream.h>

void main()
{
int i;
int j;
int sum;
cout <<"enter number ";
cin >>i;
sum=0;
j=1;
while(j<=i)
 {
  sum=sum+j;
  j=j+1;
 }//end of while loop
cout<<" triangular number "<<i<<" is "<<sum<<endl;
}// end of program

//---------------------------------------------------






// loop example 2: factors

#include <iostream.h>

void main()
{
int i;
int j;
int sum;
cout <<"enter number ";
cin >>i;
sum=0;
j=1;
while(j<=i/2)
 {
  if(i%j ==0)
     {cout<< j<<" is a factor of "<<i<<endl;
      sum=sum+j;
     } 
 j=j+1;
 }//end of while loop
cout<<"Sum of factors is  "<<sum<<endl;
}// end of program


//--------------------------------------------------

//loop example 3: fibonacci

#include <iostream.h>

void main()
{
int f1,f2,f3;
f1=1;
f2=1;
while(f1<10000000)
 {
  cout<<f1<<endl;
  f3=f1+f2;
  f1=f2;
  f2=f3;
 }//end of while loop

}// end of program




//
// example4 epidemic model

#include <iostream.h>

void main()
{

//variable
//Percentage of population in each of three groups
double infected,susceptible,removed;

//temp stores
double sickening, recovering;

//factors governing infection and recovery
double ifact, rfact;
//time
int t;

//setup
t=0;
infected = 2.0;
susceptible=98.0;
removed=0;

ifact=0.005;
rfact=0.2;

while(t<100)
 {
  sickening=ifact*infected*susceptible;
  recovering=rfact*infected;
  susceptible=susceptible-sickening;
  infected=infected+sickening-recovering;
  removed=removed+recovering;
  t=t+1;
  cout<<t<<" "<<susceptible<<" "<<infected<<" "<<removed<<endl;
 }//end of while loop
cout<<"End "<<endl;
}// end of program






Your Problems

1)  Match the braces with lines indicating which closes which opining brace:

{  {  }  {  {  }  }  {  }  }


2)


if(i<10)
  {
   cout<<"A"<<endl;
   if(i<4)
     {
      cout<<"B"<<endl;

     }

    if(i>6)
    {
       cout<<"C"<<endl;
    }
// tricky
    if(i>15)
      {
       cout<<"D"<<endl;
      }
  }

a) link braces with lines
b) add comments to closing braces
c) say what is printed out if i is initially 9
d) say what is printed out if i is initially 2
e) say what is printed out if i is initially 5
f) say what is printed out if i is initially 1



3) Look at this program:

#include <iostream.h>

void main()
{
int i;
i=1;
while(i<=10)
 {
  cout<<i<<endl;
  i=i+3;
 }//end of while loop
cout<<"That's All Folks! "<<endl;
}// end of program

a) Indicate the stattements that are "in the loop" (with line).
b) Which statement is the pre loop setup ("Setup").
c) Which Statement in the loop ensures that the loop will eventually terminate ("control").
d) Which is/are the other staements in the loop ("body").
e) Which is the conditinal expression?
f) what values does i take?
g) How many times do we go through the loop?



4)Modify the program above (test on computer then copy out) so that it prints out the numbers  100  95  90  ....15  10  5  0
Hints: 
a) What might be a good values to set i to initially?
b) How much should you change it each go through? More or less?
c) what would be a useable conditional expression to stop in the right place?




5) Harder (optional): Write a program that asks the user for an integer. If the entered integer is positive the program asks prints out the square (i*i).
and continues to ask for more integers. When a negative or zero is entered the program exits.