Problem Set 4

What to Do

  1. Submit one of:
  2. Submit Recover
  3. Submit this form.

If you submit both versions of Filter, we’ll record the higher of your two scores.

When to Do It

By .

How to Get Help

  • Browse or search for answers on Ed or post your own questions!
  • Browse the CS50 Manual Pages for functions that might be useful.
  • Watch Shorts for any topics that you still have questions about.


  • Try out any of David’s programs from Week 4.
  • If you see any errors when compiling your code with make, focus first on fixing the very first error you see, scrolling up as needed. If unsure what it means, try asking help50 for help. For instance, if trying to compile hello, and
    make filter

    is yielding errors, try running

    help50 make filter