We sometimes use the abbreviation doc for the word doctor, but note that not all browsers display an abbreviation element in the same way (some show dots underneath, for example).

This is emphasized text, while this is strong text.

A frequently used key on most keyboards is the ESC key.

In C++ we use code like this to terminate a line: cout << endl;

You never know when some sample text will be useful.

A binary tree is a tree that is either empty or has a left subtree and a right subtree, each of which is again a binary tree.

We should probably cite Knuth [1997] for more on fundamental algorithms.

In calculus we often use the variables x and y.