2. How program execute
Welcome the user
• Find the main
• Start at the top
Get info from the
main () { User (user’s age)
• Execute each line
of code from top to Print out
bottom until the The users age
program ends }
Thank the user
3. Let the program decide which
instructions are executed
• What is we want to look at the user’s age
and make a decision in the program
based on it?
– For example: If they’re over 35, maybe we
want to tell the user they’re old!
– How rude!*!*!*!
4. Welcome the user
Flow Chart
Get info from the
user
Is the user yes
Over 35?
Print out
“You’re OLD”
Thank the user
5. If statements – One Alternative Only
This means that either the first
int age; statement after the if is executed when
cout << “Welcomen”; running your program OR it is
ignored completely.
cout << “Enter you age: “;
cin >> age; If the comparison is true - the if
statement is executes
If the comparison is false - the if
statement is ignored.
if (age > 35)
cout << endl<<“You’re old n”;
cout <<“Thanks for running
me”;
6. Let the program decide which
instructions are executed
• Let’s do something a little different
– If they’re over 35, let’s tell the user they’re old!
– If they’re under 35, let’s tell the user they’re
young!
7. Welcome the user Flow Chart
Get info from the
user
Is the user yes
Over 35?
Print out
Print out “You’re OLD”
“You’re YOUNG”
Thank the user
8. If- else statements – 2 alternatives
int age; Either the first statement is
cout << “Welcomen”; executed OR the second
cout << “Enter you age: “; statement is executed.
cin >> age;
BOTH sets of statements are
NEVER used.
if (age > 35)
cout << endl<<“You’re old n”;
else ONE OR THE
cout << endl<<“You’re OTHER!
young n”; If the comparison is true - the
first set is used;
cout <<“Thanks for running me”; If the comparison is false - the
second set is used;
10. If- else if statements- Multiples
Alternatives. What’s the difference?
int age;
cout << “Welcomen”; If the if comparison is true – execute
cout << “Enter you age: “; its block of code and jump out.
cin >> age;
If it’s false, check the next else-if. If the
comparison is true - execute its block
if (age > 35) of code and jump out.
cout << endl<<“You’re old n”;
else if (age < 35)
cout << endl<<“You’re young n”;
cout <<“Thanks for running me”;
11. • Wait….
• What if the user IS 35?
• Let’s tell them that we’re not sure yet if
they’re young or old. But in a year, we’ll
let them know!
12. Welcome the user Flow Chart
Get info from the
user
<35 >35
How old is
the user
=35
Print out Print out Print out
“You’re YOUNG” “The jury’s still out” “You’re OLD”
Thank the user
13. If – else if statements
int age;
cout << “Welcomen”;
cout << “Enter you age: “; If the if comparison is true – execute
cin >> age; its block of code and jump out.
if (age > 35) If it’s false, check the next else-if. If
cout << endl<<“You’re old n”; the comparison is true - execute its
else if (age < 35) block of code and jump out.
cout << endl<<“You’re young n”;
else if (age == 35) If it’s false, check the next else-if. . If
cout << endl<<“The jury’s still out! n”; the comparison is true - execute its
block of code and jump out.
cout <<“Thanks for running me”;
15. If – else if - else statements
int age;
cout << “Welcomen”;
cout << “Enter you age: “; If the if comparison is true – execute
cin >> age; its block of code and jump out.
if (age > 35) If it’s false, check the next else-if. If
cout << endl<<“You’re old n”; the comparison is true - execute its
else if (age < 35) block of code and jump out.
cout << endl<<“You’re young n”;
else If it’s false, do the else
cout << endl<<“The jury’s still out! n”;
IF NO CONDITION IS TRUE, THE
ELSE IS EXECUTED. IT’S A
cout <<“Thanks for running me”; CATCH ALL
16. Compound if statements...
You might want more than a single statement to be
executed given an alternative...so instead of a single
statement, you can use a compound statement
if (logical expression)
{
Many C++ statements;
}
else //optional
CS161 Week #3 16
17. Relational operators
> greater than 5 > 4 is TRUE
< less than 4 < 5 is TRUE
>= greater than or equal 4 >= 4 is TRUE
<= less than or equal 3 <= 4 is TRUE
== equal to 5 == 5 is TRUE
!= not equal to 5 != 4 is TRUE
18. Guided Lab 4
Remember our guided lab that
converted inches to millimeters? Let’s
make it better!
Ask The user if they want to convert
inches to millimeters or millimeters to
inches. Based on their answer, we’ll
do the corresponding conversion for
them.
CS161 Week #3 18
19. Guided Lab 4 - Algorithm
Start with you algorithm!
Step 1: Welcome the user
Step 2: Get info from user
Do they want to convert from inches to mm or mm to inches?
How many inches or millimeters do they want to convert
Step 3: Do Calculations
If they want to convert to mm, then mm = inches*25.4;
If the want to convert to inches, then (look it up)
Step 4: Output the result
___ inches converts to ___ mm OR
___ mm converts to ___ inches
Step 5: Thank the user for running your program,
CS161 Week #3 19
20. Guided Lab 4
#include <iostream>
using namespace std;
//header
int main() {
//declare variables
char selection; //the user’s answer…one character
float inches, mm;
//Step 1: prompt for input from the user
cout << “Enter i to convert to inches”
<< “ and m to convert to mm: “;
cin >> selection; //get the response
cin.get(); CS161 Week #3 20
21. Example of if Statements
// look at what’s inside the selection variable
// if if’s m, run code to convert inches to mm
if (‘m’ == selection) //notice expression!
{
//Get inches from the user
cout << “Enter the # inches: “;
cin >> inches; cin.get();
//Do the conversion
mm = 25.4 * inches; //this is multiplication!
//Print out the results
cout << inches << “in converts to ”
<< mm << “ millimeters” << endl;
}
CS161 Week #3 21
22. Example of if Statements
else //selection is not an ‘m’. Convert to inches
{
//Get mm from the user
cout << “Enter the # millimeters: “;
cin >> mm; cin.get();
//Do the conversion
inches = mm / 25.4;
//Print out the results
cout << mm << “mm converts to ”
<< inches << “ inches” << endl;
}
CS161 Week #3 22
23. Or, use the else if sequence…
else if (‘i’ == selection) //selection is not an ‘m’
{
cout << “Enter the # millimeters: “;
cin >> mm; cin.get();
inches = mm / 25.4; //this is division
cout << mm << “mm converts to ”
<< inches << “ inches” << endl;
}
else
cout << “Neither i nor m were selected” << endl;
CS161 Week #3 23
25. Assignment 4
• You’ve been hired by a cell phone company to write a
program that calculates customers’ monthly bill. Here is
the information you are given.
• The plan costs $60 each month for 200 free minutes,
250 texts and 2GB of data. Additional minutes costs 40
cents per minute. Additional texts cost 20 cents per text.
Additional data costs $10 for each GB over (rounded
up).
• Write a program that will ask the customer how many
minutes they have used, how many texts they have
sent/received, and how much data they’ve used that
month and print out their monthly bill.
26. Assignment 4
• For example, if a customer
– uses their cell phone for 250 minutes,
– sent/received 300 texts messages,
– used 4GB of data
– they will be charged $60(plan cost) + 50 (additional minutes)*.40
(cents per minute) + 50 (additional text)*.20 (cents per text) + 2
(additional GB)*10 (dollars per GB) = $110.00 that month.
• Your program output should look like:
– Plan Fee: 60.00
– Additional Minutes Fee: $20.00
– Additional Texting Fee: $10.00
– Additional Data Fee: $20.00
– Total Monthly Cost: $110.00
27. Challenge 4
If you made
it this far,
you can
finish the
job, Ropes?
Who needs
ropes!
28. Challenge 4
• Adding on to assignment 4: your customers can choose their plan type too.
They can sign up for either the standard plan or the premium plan.
• Like assignment 4, the standard plan costs $60 each month for 200 free
minutes, 250 texts and 2GB of data. Additional minutes costs 40 cents per
minute. Additional texts cost 20 cents per text. Additional data costs $10 for
each GB over (rounded up).
• The premium plan costs $100 each month for 300 free minutes, 300 texts and
3GB of data. Additional minutes costs 30 cents per minute. Additional texts
cost 15 cents per text. Additional data costs $10 for each GB over (rounded
up).
• Write a program that will ask the customer their plan type in addition to all the
other input from assignment 4.
• Your program will output the plan type chosen, the additional fees (for the
chosen plan type) and the customers monthly bill.
