Hints for CS50x

Getting Started

Writing Code

David introduces the CS50 Codespace at the beginning of Lecture 1. If you are a beginner, please do not try to set up your own computer to do the course but use the CS50 Codespace as David does throughout the course. You will save yourself a lot of headaches. 🙂

Here’s the link to open the Codespace

Compiling your programs

FAQ: I’m trying to compile my program and I get “ no rule to make target ‘population’ “ How do I fix that?

You probably see a prompt in your terminal with just $ which indicates that you have not attached your terminal to the folder/directory where you have saved your population.c source code. Be sure to cd population to move into that folder first. You can then confirm your file is there by running ls and you should see population.c. Now, you can run make population to compile your program.

Here’s a clip from lecture 1 where David illustrates this issue, if you’d like to review:

Problem Set 2 - Caesar

FAQ: I don’t understand the Caesar formula and how the modulo 26 fits in. Why do we use that?

FAQ: Caesar check50 says I’m failing, but it looks right to me

Problem Set 3 - Tabulate

FAQ: I’m not sure how the whole Tabulate process is meant to work in Runoff. I’ve watched the Walkthrough but I’m still confused!

Problem Set 4 - Filter

You may find it easier to debug your filters using a smaller bitmap file than the ones given in the distribution code.

• A small 3x3 bitmap(wget http://github.com/curiouskiwi/cs50x-help/raw/master/3x3.bmp)
• A small 3x3 bitmap for Edges(wget http://github.com/curiouskiwi/cs50x-help/raw/master/3e.bmp)
• A small 4x4 bitmap(wget http://github.com/curiouskiwi/cs50x-help/raw/master/4x4.bmp)
• A small 4x4 bitmap for Edges(wget http://github.com/curiouskiwi/cs50x-help/raw/master/4e.bmp)

Problem Set 4 - Recover

FAQ: What does that final condition in the JPG signature check mean?

Lab 5 - Inheritance

FAQ: I don’t get how you use recursion to free the entire family?

Problem Set 5 - Speller

A simple hash function you can try

Problem Set 7 - Finance

Sometimes you may want to test your quote/buy/sell/index functions using prices/stocks that you know won’t change. Or, the IEX API may be acting up and isn’t returning any values. In these cases, a temporary lookup function in helpers.py works well. Open helpers.py and comment out the lookup function and then paste in this lookup function for testing.

Final Project

Be sure that your README.md is comprehensive enough, per the requirements shown in the specification. Here’s an example of a project README file that I did for my own project years ago.

Other Concepts you might need to know

I created a string like string word = "hello";Why do I segfault when trying to change a character in that string?

Just for Fun

Wondering how to display the binary representation of a hex number? Here’s my hex to binary converter in C.