Update prerequisite knowledge section - Added, in my pinion, much better resources for the topics of how computers execute programs and instructions

README.md

@@ -487,8 +487,10 @@ Write code on a whiteboard or paper, not a computer. Test with some sample input
         - [answers to questions](https://github.com/lekkas/c-algorithms)
 
 - [ ] **How computers process a program:**
-    - [ ] [How does CPU execute program (video)](https://www.youtube.com/watch?v=42KTvGYQYnA)
-    - [ ] [Machine Code Instructions (video)](https://www.youtube.com/watch?v=Mv2XQgpbTNE)
+    - [ ] [How computers calculate - ALU (video)](https://youtu.be/1I5ZMmrOfnA)
+    - [ ] [Registers and RAM (video)](https://youtu.be/fpnE6UAfbtU)
+    - [ ] [The Central Processing Unit (CPU) (video)](https://youtu.be/FZGugFqdr60)
+    - [ ] [Instructions and Programs (video)](https://youtu.be/zltgXvg6r3k)
 
 ## Algorithmic complexity / Big-O / Asymptotic analysis
 - nothing to implement