Description
Objectives
- Compile and run C++ code
- Take user inputs and produce outputs
- Understand C++ data types
- Perform arithmetic operations
You can find the summary note (hw2 note: HelloWorld, data type) on Moodl e.
Questions
Question 1 (5pt): Hello World
The first program that we usually write in any language we’re learning is Hello, World . Create a program that prints “Hello, World! ” to the screen (the console window in Cloud9).
Expected output
Hello, World!
The file should be named helloWorld.cpp
Here are some suggested steps:
Step 1: Open an Empty File
In Cloud9, select File -> New File . A new, blank file called Untitled1 will be opened.
Step 2: Your First Code
Starting on line 1 in Untitled1, type the following code.
Step 3: Saving Your File
Save the file: go to File -> Save As… A dialog box will open. Name it helloWorld.cpp and save it in the hmwk2 folder.
Note: make sure you save it with the .cpp extension or it will not compile correctly!
The .cpp extension on the filename tells Cloud9 that the file should be read in the C++ programming language. Once you save it, the lines in the file should be color-coded to reflect what they do in the program. This is called syntax highlighting.
Important: You should save your work frequently in Cloud9 to avoid losing your work in the event of the program crashing. Also, you should take a backup of your Cloud 9 environment.
Step 4: Running Your Code
To run the program, click on the icon with the green arrow next to the word Run. If it works, you should see new terminal tab window open at the bottom. The title of the tab shows the file being run
(hmwk2/ helloWorld.cpp), and inside the window you should see “Running ….” (again the name and full path of the file), and underneath it, the output of our program: “Hello, World! ”
Step 5: Running Your Code from Command Line
Move to the “bash” tab (the first tab in the bottom panel). Right-click again and Clear the Buffer.
Make sure you are inside the hmwk2 directory. Type:
$ g++ helloWorld.cpp -g -std=c++11
the - g option turns on debugging, which we will use later in the semester, so we should get used to it.
the - std=c++11 option makes sure that the c++ version used to run the program is c++ 11. If you don’t give this option then default version(which is usually C++98) is used.
This creates an executable called “a.out” (see figure below). You can run it by typing
$ ./a.out
Since no executable name was specified to g++, a.out is chosen by default. You can alternatively use the “-o” option to change the name :
$ g++ helloWorld.cpp -g -std=c++11 -o hello
creates an executable called “hello ” (see figure below). You can run it by typing
$ ./hello
Notice the output in the same: Hello, world!, followed by the return of the prompt, for new commands.
Question 2 (5pt): Hello You!
If a program is more interactive, it’s fun! Create a program that takes a name and print prints “Hello, <name>! ”. Your output should be exactly the same as below, including the prompt for the user input.
Expected output (bold is user input)
Enter your name:
Malvika
Hello, Malvika !
Question 3 (10pt): Carnot efficiency
In thermodynamics, the Carnot efficiency is the maximum possible efficiency of a heat engine operating between two reservoirs at different temperatures. The Carnot efficiency is given as η = 1 − TTHC
where T C and T H are the absolute temperatures at the cold and hot reservoirs, respectively. Write a program that takes temperatures at the cold receiver(Tc ) and hot receiver(Th ) as integer values, and computes η the Carnot efficiency.
Expected output (bold is user input)
Enter cold reservoir temperature: 10
Enter hot reservoir temperature:
80
Carnot efficiency: 0.875
Question 4 (10pt): Calculating sphere volume and area
Create a program that takes a radius as a floating-point value (as double ) , and it prints both the volume and surface area of a sphere with the given radius. The formulas are: volume = πr3 surfaceArea = 4πr2
For π , use M_PI from #include <cmath>
Expected output (bold is user input)
| Enter a radius: 3.3
Volume: 150.533 Surface area: 136.848 |
Question 5 (10pt): Temperature conversion
In science, the temperature is always described in Celsius, but in the U.S. we tend to use Fahrenheit. Create a program that takes user input for Fahrenheit (as double ) and converts it into Celsius. The formula is:
Celsius = 59 (Fahrenheit − 32)
The calculated temperature Celsius values should be formatted with a two-digit precision as shown below. Fahrenheit value should be printed without any precision formatting applied.
Expected output (bold is user input)
Enter a temperature in Fahrenheit:
76
The temperature 76 degrees Fahrenheit is 24.44 degrees Celsius.
Question 6 (10pt): Convert seconds
Write a program that takes a number of seconds as user input (as an integer ) and converts it to hours, minutes, and seconds as shown below. You should convert the amount of time in such a way that maximizes the whole numbers of hours and minutes.
Expected output 1 (bold is user input)
Enter a number of seconds:
60
0 hour(s) 1 minute(s) 0 second(s)
Expected output 2 (bold is user input)
Enter a number of seconds:
3671
1 hour(s) 1 minute(s) 11 second(s)
Question 7 (10pt): Population
The U.S. Census provides information about the current U.S. population as well as approximate rates of change. Using those rates and the current US population, write a program that takes a current population and computes the U.S. population in exactly one year (365 days). If you end up with a non-integer projected population, then round down to the nearest whole person.
Three rates of change are provided:
- There is a birth every 8 seconds
- There is a death every 12 seconds
- There is a new immigrant arriving in the US every 27 seconds
Expected output (bold is user input)
Enter the current population:
1000000
The population in one year: 3482000
