Do I have to cite common CS algorithms? I'm working on my final thesis for a CS grade course and I want to use a common sorting algorithm (quicksort for the curious ones). Do I need to include a reference to this algorithm (cite or quote)? Or it is so common that I don't need to? Take into accout that it was first published on 1961 and it is extremely used and known by almost anyone in the CS world.
Do I have to cite common CS algorithms?


No. 

The fact that it was first published [in] 1961 isn't relevant, you needn't cite it because it is [widely] used and [well-]known by almost anyone in the CS world. 

That said, although a citation isn't necessary, you can provide one at your discretion. Such a citation is probably more important for a final thesis than for an academic publication, since it may be considered important for students to demonstrate they can cite. 

Beyond citing the original source, you may like to cite your favourite textbook(s) on the topic (rather than citing the entire volume, reference a particular section, e.g., \cite[Chapter 4.3]{Textbook} in LaTeX).