CS 246 Assignment 1

Like all assignments, you will complete this assignment via GitHub. See the submission instructions for how to get the starter code and how to submit this assignment.

(If you end up with the assignment files in a .zip file, you can say unzip xxx.zip to unzip it, where xxx.zip is the name of your downloaded file. As always, make sure you are in the right working directory. Use ls and pwd to see where you are.)

Please complete these tasks in order. It’s meant to be easier that way. Also, ignore the possibility of bogus input. For example, if your program is expecting a number and the user types bogus, it’s OK if your program crashes.

Sign up for a GitHub account and fill out the course survey.
Hello, world!

Edit the hello.c file (which contains only comments – fill in the header here and in the other files below) to implement a “Hello, world!” program. This program should simply print Hello, world! on a line by itself and then exit successfully.

You will be able to compile your program with gcc -o hello hello.c and run it with ./hello. (The ./ there says that the hello executable is in the same directory as you are.)
Adding two numbers

Edit the add2.c file to write a program that asks the user for two numbers (just use ints, like everyone else always does) and then prints their sum. Here is an example session, with user-entered numbers in boldface:

Enter a number: 4
Enter a number: 7
4 + 7 = 11

This program can be compiled with gcc -o add2 add2.c and run with ./add2.
Adding lots of numbers

Edit the adds.c file to write a program that adds many numbers together. It continues accepting numbers until the user enters a 0. (Who would need to add a 0, anyway?) It then prints the sum of the numbers. It does not need to repeat back the numbers entered. (That would require an array, and we haven’t learned about them yet.)

Here is an example session:

Enter a number: 4
Enter a number: 7
Enter a number: 1
Enter a number: 18
Enter a number: 0
Sum: 30
A calculator

Edit the calc.c file to write a very simple calculator program. It should ask the user for an operation, which is +, -, *, or /. After asking for the operation, the program then asks for 2 numbers. The program then prints out the operation applied to the two numbers. It loops until the user chooses 0 as the operation.

You should read in the command as a char. This will make your life simpler.

Here is an example session:

Enter an operation: -
Enter a number: 6
Enter a number: 2
6 - 2 = 4
Enter an operation: *
Enter a number: 4
Enter a number: 9
4 * 9 = 36
Enter an operation: /
Enter a number: 10
Enter a number: 4
10 / 4 = 2
Enter an operation: 0
Good-bye.

Note that your program should do integer division. If you store your numbers as ints, this should be the default behavior. (That is, integer division is the natural, easy interpretation of this task.)

Your program should act appropriately (issue a sensible error and continue running) if the user types in the character for an operation that does not exist (for example, '#') or tries to divide by 0. You are not expected to be able to handle when the user types a word instead of a number, however.

NB: When you use scanf("%d",...), you will read only the number that the user types in, not the newline after the number. So if you read a character later on, you’ll read the newline by mistake. The solution is to put a space in the format string before the %c. As the first bullet on page 45 of our book explains, this space character instructs scanf to skip any whitespace, including a newline.
Reflections

Edit refl.txt (short for “reflections”) to answer the questions therein.

When you’re all done, submit on GitHub by creating a Pull Request according to these instructions.