The notes only indicate what has been taught in classes, and are not a substitution for reading the textbook. Paper copy of the notes is also available in the 1st Year Lab.
Computer knows only zeros and ones.
In order to make computer to do its work, one must be able to speak it's language or otherwise use a translator. In fact, the translation is the usual way. But most of the time, when we say memory, we mean usually the main memory. These are the hardware. Software refers to the computer programs, something like the above.