C Kickstart

You received an email from GitHub: “FiratUniversity-IJDP-SoftEng has invited you to join”. Open it and click Join, or go to github.com/FiratUniversity-IJDP-SoftEng and accept the banner at the top. Make sure you are signed in with the same GitHub account you used for Lab 1.

No email? Check spam, then tell the instructor your GitHub username.

1. Click the orange Accept lab lab02 button at the top of this page. Sign in with GitHub if asked and authorize Classroom 50.
2. Click Accept assignment. A checklist runs for about 20 seconds while your repository is created.
3. Click Open repository.

You now own a private repository called introduction-to-computer-science-lab02-yourusername. Only you and the instructor can see it.

On your repository page: green Code button → Codespaces tab → Create codespace on main.

VS Code opens in your browser. The first start takes a couple of minutes while gcc, make, valgrind and the tests are installed; watch the terminal at the bottom until it shows a prompt ending in $.

In the terminal:

$ python3 check.py:| hello.c prints "hello, world"
  expected 'hello, world\n', got 'hello, TODO\n'
...
0/14 checks passed

Everything fails because nothing is done yet. Your job is to turn the list green, part by part.

Open hello.c. One word is wrong. Make it print exactly hello, world with a newline, then compile and run:

$ make hello$ ./hellohello, world

If the compiler complains, read the first error; it names the line.

greet.c asks for a name with get_string and stores it in name. Complete the printf so that it prints hello, followed by the name and a newline. %s is the placeholder, and the value goes after the format string, separated by a comma, exactly like hello2.c in the lecture.

$ make greet$ ./greetWhat's your name? Firat
hello, Firat

bits.c asks for a number from 0 to 255 and loops over its 8 bits; bit is already 1 or 0. Replace the two ? so that it prints '1' when bit is 1 and '0' otherwise.

$ make bits$ ./bitsNumber (0–255): 73
01001001

That is last week’s bit widget, now in C.

Write a program that asks for a height from 1 to 8, re-prompting until it gets one, and prints a right-aligned pyramid:

$ make mario$ ./marioHeight: 4
 #
##
###
####

Plan it before you type. Row 1 has three spaces and one #; row 2 has two spaces and two #; in general row i has height - i spaces and i hashes. So:

1. A do … while that asks for height until it is between 1 and 8 (lecture: mario7.c).
2. An outer for over the rows, i from 1 to height.
3. Inside it, one for that prints height - i spaces, then one for that prints i hashes, then printf("\n").

Read two integers x and y and print five lines: the sum, the difference, the product, the quotient as a real number with two decimals, and the remainder. If y is 0, print the word undefined for the last two lines instead of dividing.

$ make calculator$ ./calculatorx: 7
y: 2
9
5
14
3.50
1

Two traps from the lecture: x / y with ints truncates, so cast first, (float) x / (float) y; and printf("%.2f\n", z) prints two decimals. Dividing by zero crashes a C program, so the if (y == 0) must come before the division.

Ask for an amount of change in cents (re-prompt while it is negative) and print the minimum number of coins using quarters (25), dimes (10), nickels (5) and pennies (1).

$ make cash$ ./cashChange owed: 41
4

41 = 25 + 10 + 5 + 1. The strategy is greedy: always take the largest coin that still fits. Two ways to write it: a while (cents >= 25) loop per coin, or arithmetic: cents / 25 is how many quarters fit and cents % 25 is what is left. Both are correct; the second is four lines shorter. Try 0, 1 and 99 by hand before you trust the tests.

When python3 check.py shows 14/14 checks passed (or when you have done what you can), push. Every push is graded.

$ git add -A$ git commit -m "Lab 2"$ git push

Prefer buttons? Source Control icon on the left of VS Code: type a message, click Commit, then Sync Changes.

About two minutes after the push:

1. On your repository page, look under Releases on the right. The newest release shows your score out of 10 and a table of the six parts.
2. Or on classroom50.org, open the assignment and click My submission.

Push as often as you like before Friday, October 9, 23:59; the last push before the deadline counts. Pushes up to five days late lose 10% per day.