Clarify OSTEP: add missing link, fix prerequisite

README.md

@@ -226,7 +226,7 @@ Courses | Duration | Effort | Additional Text / Assignments| Prerequisites | Dis
 :-- | :--: | :--: | :--: | :--: | :--:
 [Build a Modern Computer from First Principles: From Nand to Tetris](https://www.coursera.org/learn/build-a-computer) ([alt](https://www.nand2tetris.org/)) | 6 weeks | 7-13 hours/week | - | C-like programming language | [chat](https://discord.gg/vxB2DRV)
 [Build a Modern Computer from First Principles: Nand to Tetris Part II ](https://www.coursera.org/learn/nand2tetris2) | 6 weeks | 12-18 hours/week | - | one of [these programming languages](https://user-images.githubusercontent.com/2046800/35426340-f6ce6358-026a-11e8-8bbb-4e95ac36b1d7.png), From Nand to Tetris Part I | [chat](https://discord.gg/AsUXcPu)
-[Operating Systems: Three Easy Pieces](coursepages/ostep/README.md) | 10-12 weeks | 6-10 hours/week | - | [strong C programming](/coursepages/ostep/README.md#prerequisites) | [chat](https://discord.gg/wZNgpep)
+[Operating Systems: Three Easy Pieces](coursepages/ostep/README.md) | 10-12 weeks | 6-10 hours/week | - | Nand to Tetris Part II | [chat](https://discord.gg/wZNgpep)
 [Computer Networking: a Top-Down Approach](http://gaia.cs.umass.edu/kurose_ross/online_lectures.htm)| 8 weeks | 4–12 hours/week | [Wireshark Labs](http://gaia.cs.umass.edu/kurose_ross/wireshark.php) | algebra, probability, basic CS | [chat](https://discord.gg/MJ9YXyV)
 
 ### Core theory

coursepages/ostep/README.md

@@ -26,7 +26,7 @@ The code you'll read is fairly simple and presented in short fragments. The book
 
 You will also write a little bit of C code. Only a minority of the chapters (about 10 out of 50) ask you to write some C code (while the other chapters require you to run provided simulation code and answer questions). These are usually simple, short C programs that imitate the code that was presented in that chapter, with small modifications.
 
-If you are getting stuck on these, please don't spend too much time on them. There is a great solution set here. There is no honor code for this, so you are free to use the solutions. If you find yourself spending too much time, feel free to read and understand the solutions instead. Your main priority should be to gain understanding of operating systems concepts, not to master C coding.
+If you are getting stuck on these, please don't spend too much time on them. There is a great solution set [here](https://github.com/xxyzz/ostep-hw). There is no honor code for this, so you are free to use the solutions. If you find yourself spending too much time, feel free to read and understand the solutions instead. Your main priority should be to gain understanding of operating systems concepts, not to master C coding.
 
 ## Extended Approach