Computer Science and Programming for a complete novice everyone! 
I am going to learn mathematics in a university, but it will be rather ''pure'' math, so, I want to get some exposure to computer science on my own. The problem is, I've never tried any programming or computer science activities. I'm not sure where should I start. Now, I realise that internet is full of online or video courses about cs or codes, but they are specific, for example, ''how to learn C++/Python'' or ''algorithms''.
As far as I'm concerned, what I need is some kind of introductory book for computer science( basics, how this and that works and why, what is this and what is that ). Though, some people say that it's better to learn some programming language first even before getting exposed to theoretical material. 
Thanks in advance, I will appreciate any answers.
I started progamming as a kid and (at adulthood) graduated in Computer Science. I really don't know what's the best to learn first.

Computer Science is a breed of mathematics and programming is a craftworking. To implement the ideas of the first you must use the second.

IMHO programming is something you learn by demand while CS is a knowledge you study by passion.

The modern languages today (C#, Java, Javascript) are complex tools of trade and one learning it must dive in to learn it idiosyncracies (and not to mention the libraries and frameworks like jQuery, Hibernate, etc).

So while you are not willing to become a pro programmer I can advice you to use more "crude" languages like C||C++.

To get start in CS go to the basics: Algorithms.

There are a lot of classical and well studied problems like sorting, path finding/evalutaion, finding substring, etc. 

While studing these problems you can learn how to implement some know solutions again IMHO that's can the best approach to get starting.