Clarify OSTEP Options

Direct most students to read OSTEP and complete homework.
Direct only students specializing in systems to undertake
the course projects

Resolves #1083

Co-authored-by: Waciuma Wanjohi <code@waciuma.com>
Co-authored-by: spamegg <spamegg@pm.me>

coursepages/ostep/README.md

@@ -3,23 +3,46 @@
 Credit goes to [palladian](https://github.com/palladian1)
 ## Introduction
 
-First, we should be frank: it's really hard to find a good self-contained online course on operating systems. OSTEP is the best course we've found so far, but it does have some issues.
+First, we should be frank: it's really hard to find a good self-contained online course on operating systems. OSTEP is the best course we've found so far. We describe below two approaches to the course, a "Base" approach which is suitable for most students, and an "Extended" approach, which is appropriate for students intending to specialize in systems programming.
 
-This is the first course in the OSSU curriculum for which you'll need to learn some prerequisites on your own before starting it, in addition to the courses that come before it in the curriculum. You might also run into some issues running the scripts for homework demos and for testing your solutions to the projects (although we hope we've solved most of those by now).
+The "base" approach covers all of our operating system curriculum requirements and should take about 80 hours of work.
 
-What this means for you is that if you're under a significant time crunch, or you're just not all that interested in systems programming and OS development, there's no shame in skipping this course and coming back to it later. You could also do only a part of the course (e.g. you might choose to skip the homework and/or projects).
+The "extended" approach contains all of the work of the base approach and more. It involves learning very serious C and x86 assembly, and delving deep into kernel programming. It takes significantly more time (over 200 hours) and is much more challenging. For those students interested in this area of computing it is also highly rewarding.
+
+## Base Approach
+
+1. Read through the free online textbook Operating Systems: Three Easy Pieces
+2. Complete the homework questions at the end of each chapter. (There is an associated [Github repository](https://github.com/remzi-arpacidusseau/ostep-homework) for the homeworks.)
+
+This should take about 8 weeks, 10 hours/week. That's all you need to do!
+
+You will need a Unix/Linux system, some basic command line tools, and a C compiler (such as GCC or Clang). On Windows, you can install Ubuntu in a virtual machine, or use WSL (Windows Subsystem for Linux). Mac OS is Unix-like, so it should be OK to use.
+
+Question: I see some C code in this book. How much C do I need to know?
+
+Answer: You'll need to read and understand some C code in this book. You'll need basic understanding of arrays, pointers and print formatting. You can consult the free book Modern C by Jen Gustadt. The CS50 Manual pages are also helpful to look up functions. You shouldn't spend too much time on learning C.
+
+The code you'll read is fairly simple and presented in short fragments. The book helps you out quite a bit by manually introducing many C APIs such as the Process API, the Thread API, and so on. You can type, compile and run the code fragments, and read the corresponding explanations. The book explains them in great detail in a conversational style that's fun to read.
+
+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.
+
+## Extended Approach
+
+If you've chosen this option, then this is the first course in the OSSU curriculum for which you'll need to learn some prerequisites on your own before starting it, in addition to the courses that come before it in the curriculum. You might also run into some issues running the scripts for homework demos and for testing your solutions to the projects (although we hope we've solved most of those by now).
 
 That said, if you're able to commit the time required for the prerequisites, we believe the reward is well worth the effort: this course is exciting, interesting, and quite useful for other fields of computer science and programming. One big attraction of this course is the opportunity to see a simplified but fully-functional Unix-like operating system in action and understand the concepts and design decisions that went into it as well as the low-level implementation details.
 
-In order to satisfy OSSU's curricular guidelines, you should either watch all the lecture videos or read chapters 1 through 47 in the textbook (don't worry, the chapters are usually just a few pages long) as well as finish the projects listed below. We also strongly encourage you to do the homework exercises as they're assigned on the course website or in the book chapters; think of these like the "check-your-understanding" questions that pop up in the middle of lecture videos on sites like Coursera or edX.
+You should either watch all the lecture videos or read chapters 1 through 47 in the textbook (don't worry, the chapters are usually just a few pages long) as well as finish the projects listed below. We also strongly encourage you to do the homework exercises as they're assigned on the course website or in the book chapters; think of these like the "check-your-understanding" questions that pop up in the middle of lecture videos on sites like Coursera or edX.
 
-## Prerequisites
+### Prerequisites
 
 This class requires a lot of experience programming in C. You should finish one of the C books listed in the [resources below](#c) *before* starting this course; if you try to learn C at the same time as the course material, you're likely to feel overwhelmed. If you haven't used C before, you should expect to spend a lot of time on this; it's hard to predict how long it might take for each person, but a rough estimate might be 8-10 hours per week for 3-5 weeks. You can always learn C alongside another OSSU course or even redo the exercises for other courses in C to gain practice with it.
 
 You should also finish both parts of Nand2Tetris before starting this course. OSTEP focuses on the real-world x86 and x86_64 architectures, so you'll have to fill in some gaps in order to translate the concepts you learned in Nand2Tetris to a new architecture. You can do that with the x86 resources below, but note that they all assume you know C, so learn that first. This should take around 6-8 hours in total.
 
-## Course Links
+### Course Links
 
 * [Course website](https://pages.cs.wisc.edu/~remzi/Classes/537/Spring2018/)
 * [Book](https://pages.cs.wisc.edu/~remzi/OSTEP/)
@@ -29,7 +52,7 @@ You should also finish both parts of Nand2Tetris before starting this course. OS
 * [Projects](https://github.com/remzi-arpacidusseau/ostep-projects)
 * [xv6](https://github.com/mit-pdos/xv6-public)
 
-## Roadmap
+### Roadmap
 
 This course was originally taught as CS 537 at the University of Wisconsin by the author of the OSTEP textbook, so the projects are assigned in the course according to the best times to give UWisconsin students access to on-campus resources like recitation sections and office hours. That means they don't match up perfectly with the material being covered at that time in the lectures or textbook chapters. We recommend doing the course in the following order instead.
 
@@ -97,10 +120,9 @@ git clone https://github.com/mit-pdos/xv6-public src
 - [hints for `scheduling-xv6-lottery`](Scheduling-xv6-lottery.md)
 - [hints for `vm-xv6-intro`](vm-xv6-intro.md)
 
+### Resources
 
-## Resources
-
-### C
+#### C
 
 Please don't try to learn C from sites like GeeksforGeeks, TutorialsPoint, or Hackr.io (we're not even gonna link to them here). Those are great resources for other languages, but C has way too many pitfalls, and C tutorials online are often filled with dangerous errors and bad coding practices. We looked at many C resources for the recommendations below and unfortunately found *many* bad or unsafe ones; we'll only include the best ones here, so look no further!
 
@@ -117,7 +139,7 @@ Additional (***optional***) resources include:
 * [Secure Coding Practices in C and C++](https://www.amazon.com/dp/0321822137): if you want to understand why other C resources are so unsafe.
 * [*The C Programming Language*](https://www.amazon.com/dp/0131103628): the original book on C by its creators. Too outdated for OSTEP, but a good read if you manage to find a copy.
 
-### x86 Architecture and Assembly Language
+#### x86 Architecture and Assembly Language
 
 Nand2Tetris has already introduced most of the concepts you'll need to understand systems and computer architectures, so now you just need to port that knowledge to the real-world (32-bit) x86 architecture.
 
@@ -136,7 +158,7 @@ Additional (***optional***) resources include:
 * [GCC Inline Assembly HOWTO](https://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html): a guide to writing assembly code inside a C program.
 * [*Intel 80386 Programmer's Reference Manual*](https://pdos.csail.mit.edu/6.828/2018/readings/i386.pdf): the official (and huge) resourcefrom Intel.
 
-### xv6
+#### xv6
 
 You don't need to read anything about xv6 until after you start OSTEP; in fact, we recommend holding off on the xv6-related projects until you've finished the entire section on virtualization. After that, you'll need a guide to walk you through the source code.
 
@@ -148,7 +170,7 @@ However, that book glosses over a lot of the details in the code that you might
 
 Also [here](https://www.youtube.com/playlist?list=PLbtzT1TYeoMhTPzyTZboW_j7TPAnjv9XB) is an excellent video series walking through much of the xv6 code.
 
-### Miscellaneous
+#### Miscellaneous
 
 You'll need a general sense of how Makefiles work in order to use the Makefile for xv6. [This tutorial](https://makefiletutorial.com) covers much more than you need; just read the "Getting Started" and "Targets" sections and come back to the rest later if you need to look something up (but you shouldn't have to).