N0 V0w3ls

Learning Goals

  • Practice using strings
  • Practice using command-line arguments
  • Write a program entirely from scratch



If you’ve been on the internet, you might have seen “leetspeak” (or “l33tsp36k” for our purposes!), which involves the substitution of symbols for alphabetical characters, where those symbols somewhat resemble their alphabetical counterparts. In this lab, you’ll write a program to replace certain vowels with digits!

Up until now, you’ve frequently written programs for which you’ve been provided distribution code. You’ll notice when downloading the “distro” for this problem, you start with nothing more than a couple of commonly used libraries and an empty main function. In this problem, you will convert a word, which you will input at the command line, to a corresponding word with numbers replacing vowels.

  • Hints
    • Do note that the main function in the distribution code uses argc and argv. Be sure to use these!
    • Be sure to check for the correct number of command-line arguments before doing anything else in your main function.



Getting Started

  1. Log into code.cs50.io using your GitHub account.
  2. Click inside the terminal window and execute cd.
  3. At the $ prompt, type mkdir no-vowels
  4. Now execute cd no-vowels
  5. Then copy and paste wget https://cdn.cs50.net/2022/fall/labs/2/no-vowels.c into your terminal to download this lab’s distribution code.

Implementation Details

  • Implement your program in a file called no-vowels.c in a directory called no-vowels.
  • Your program must accept a single command-line argument, which will be the word that you want to convert.
  • If your program is executed without any command-line arguments or with more than one command-line argument, your program should print an error message of your choice (with printf) and return from main a value of 1 (which tends to signify an error) immediately.
  • Your program must contain a function called replace which takes a string input and returns a string output.
  • This function will change the following vowels to numbers: a becomes 6, e becomes 3, i becomes 1, o becomes 0 and u does not change.
  • The input parameter for the replace function will be argv[1] and the return value is the converted word.
  • The main function will then print the converted word, followed by \n.
  • You may want to try using the switch statement in your replace function.

Thought Question

Why might you want to use command-line arguments rather than get_string, get_int, etc?

How to Test Your Code

Your program should behave per the examples below.

no-vowels/ $ ./no-vowels
Usage: ./no-vowels word
no-vowels/ $ ./no-vowels hello
no-vowels/ $ ./no-vowels pseudocode

You can check your code using check50, a program that CS50 will use to test your code when you submit, by typing in the following at the $ prompt. But be sure to test it yourself as well!

check50 cs50/labs/2022/fall/no-vowels

Green smilies mean your program has passed a test! Red frownies will indicate your program output something unexpected. Visit the URL that check50 outputs to see the input check50 handed to your program, what output it expected, and what output your program actually gave.

To evaluate that the style of your code (indentations and spacing) is correct, type in the following at the $ prompt.

style50 no-vowels.c

How to Submit

No need to submit! This is an optional practice problem.