The Design of the UNIX Operating System

The shell echoes everything you type, so when you type ^C, that too gets echoed (and in your case intercepted by your signal handler). The command stty -echo may or may not be useful to you depending on your needs/constraints, see the man page for stty for more information.

Of course much more goes on at a lower level, anytime you communicate with a system via peripherals device drivers (such as the keyboard driver that you use to generate the ^C signal, and the terminal driver that displays everything) are involved. You can dig even deeper at the level of assembly/machine language, registers, lookup tables etc. If you want a more detailed, in-depth level of understanding the books below are a good place to start:

The Design of the Unix OS is a good reference for these sort of things. Two more classic references: Unix Programming Environment and Advanced Programming in the UNIX Environment

Nice summary here in this SO question How does Ctrl-C terminate a child process?

"when youre run a program, for example find, the shell:

• the shell fork itself
• and for the child set the default signal handling
• replace the child with the given command (e.g. with find)
• when you press CTRL-C, parent shell handle this signal but the child will receive it - with the default action - terminate. (the child can implement signal handling too)"

I suggest you buy an embedded board such as the Beagleboard. They will give you the necessary documentation of the chipset used ( its TI ARM Cortex A8 in this case ). Start reading this chipset manual. Also, there are many Android, Ubuntu projects already implemented on beagleboard. Take them as reference and see how they've written the drivers to your specific board etc. This will give you an idea of how the kernel/drivers interact with the H/W.

Coming to the S/W part of the kernel, I suggest you read a good book on Operating systems in general and Linux/Unix OS in particular. This will give you fair ideas of what is a kernel and how it manages things. Then, you can play around with your desktop linux by writing small kernel modules, inserting and removing it, debugging it etc.

Also, keep a handy reference of the kernel source with you and make the internet your best friend.

In a typical real system, each separate device would in fact be running in parallel (i.e., on its own thread), but it certainly makes sense to model it in your simulation as a separate thread. You'll want to make sure that you implement some sort of analog to the interrupt system in real CPUs to handle the synchronization when the worker has finished its job (e.g., a new priority queue to catch "I/O interrupts" and the like). You may find it helpful to pick up a copy of The Design of the UNIX Operating System by Maurice Bach. It goes into great detail on how UNIX interacts with the underlying hardware, and may be a good resource for your project.

The threads of a process all share the same address space, not the same CPU registers. The thread scheduling is done depends on the programming language and the O/S. Usually there are explicit scheduling points, such as returning from a system call, blocking awaiting I/O completion, or between p-code instructions for interpreted languages. Some O/S implemtations reschedule depending on how long a thread has run for time-based scheduling. Often languages include a function that explicitly offers the CPU to any other thread or process by transferring control to the process or thread scheduler component of the O/S.

The act of switching from one thread or process to another is known as a context switch and is carefully tuned code because this is often done thousands of times per second. This can make the code difficult to follow.

The best explanation of this I've ever seen is http://www.amazon.com/The-Design-UNIX-Operating-System/dp/0132017997 classic.

You might want to read or skim a book that describes the Linux Kernel before looking deep into the Linux kernel.

The books that come to mind are:

• Understanding the Linux Kernel, Second Edition
• Design of the UNIX Operating System

OK, if you don't have any real experience in low-level embedded coding (relevant to device drivers), RTOS or OS design in general, file systems, data structures, algorithms, interfaces, etc. And, if you have "hobby level" experience with Assembler, C and C++. And, if your intent is to write a desktop OS, from the ground up, without making use of existing technologies, drivers, file systems, memory management, POSIX, etc. Here's a list of books that could be considered required reading before you can really start to write specifications and code. Pick twenty of these and that might be a good start.

In no particular order:

1- http://www.amazon.com/C-Programming-Language-2nd-Edition/dp/...

2- http://www.amazon.com/The-Answer-Book-Solutions-Programming/...

3- http://www.amazon.com/The-Standard-Library-P-J-Plauger/dp/01...

4- http://www.amazon.com/C-Traps-Pitfalls-Andrew-Koenig/dp/0201...

5- http://www.amazon.com/Expert-Programming-Peter-van-Linden/dp...

6- http://www.amazon.com/Data-Structures-In-Noel-Kalicharan/dp/...

7- http://www.amazon.com/Data-Structures-Using-Aaron-Tenenbaum/...

8- http://www.amazon.com/Mastering-Algorithms-C-Kyle-Loudon/dp/...

9- http://www.amazon.com/Code-Complete-Practical-Handbook-Const...

10- http://www.amazon.com/Design-Patterns-Elements-Reusable-Obje...

11- http://www.amazon.com/The-Mythical-Man-Month-Engineering-Ann...

12- http://www.amazon.com/The-Programming-Language-4th-Edition/d...

13- http://www.amazon.com/The-Standard-Library-Tutorial-Referenc...

14- http://www.amazon.com/API-Design-C-Martin-Reddy/dp/012385003...

15- http://www.amazon.com/The-Linux-Programming-Interface-Handbo...

16- http://www.amazon.com/Computer-Systems-Programmers-Perspecti...

17- http://www.amazon.com/System-Programming-Unix-Adam-Hoover/dp...

18- http://www.amazon.com/Memory-Programming-Concept-Frantisek-F...

19- http://www.amazon.com/Memory-Management-Implementations-Prog...

20- http://www.amazon.com/UNIX-Filesystems-Evolution-Design-Impl...

21- http://www.amazon.com/PCI-System-Architecture-4th-Edition/dp...

22- http://www.amazon.com/Universal-Serial-System-Architecture-E...

23- http://www.amazon.com/Introduction-PCI-Express-Hardware-Deve...

24- http://www.amazon.com/Serial-Storage-Architecture-Applicatio...

25- http://www.amazon.com/SATA-Storage-Technology-Serial-ATA/dp/...

26- http://www.amazon.com/Beyond-BIOS-Developing-Extensible-Inte...

27- http://www.amazon.com/Professional-Assembly-Language-Program...

28- http://www.amazon.com/Linux-Kernel-Development-3rd-Edition/d...

29- http://www.amazon.com/Version-Control-Git-collaborative-deve...

30- http://www.amazon.com/Embedded-Software-Primer-David-Simon/d...

31- http://www.amazon.com/Programming-Embedded-Systems-C/dp/1565...

32- http://www.amazon.com/Making-Embedded-Systems-Patterns-Softw...

33- http://www.amazon.com/Operating-System-Concepts-Abraham-Silb...

34- http://www.amazon.com/Performance-Preemptive-Multitasking-Mi...

35- http://www.amazon.com/Design-Operating-System-Prentice-Hall-...

36- http://www.amazon.com/Unix-Network-Programming-Sockets-Netwo...

37- http://www.amazon.com/TCP-Illustrated-Volume-Addison-Wesley-...

38- http://www.amazon.com/TCP-IP-Illustrated-Vol-Implementation/...

39- http://www.amazon.com/TCP-Illustrated-Vol-Transactions-Proto...

40- http://www.amazon.com/User-Interface-Design-Programmers-Spol...

41- http://www.amazon.com/Designing-Interfaces-Jenifer-Tidwell/d...

42- http://www.amazon.com/Designing-Interfaces-Jenifer-Tidwell/d...

43- http://www.amazon.com/Programming-POSIX-Threads-David-Butenh...

44- http://www.intel.com/p/en_US/embedded/hwsw/software/hd-gma#d...

45- http://www.intel.com/content/www/us/en/processors/architectu...

46- http://www.intel.com/p/en_US/embedded/hwsw/hardware/core-b75...

47- http://www.hdmi.org/index.aspx

48- http://en.wikipedia.org/wiki/Digital_Visual_Interface

49- http://www.amazon.com/Essential-Device-Drivers-Sreekrishnan-...

50- http://www.amazon.com/Making-Embedded-Systems-Patterns-Softw...

51- http://www.amazon.com/Python-Programming-Introduction-Comput...

52- http://www.amazon.com/Practical-System-Design-Dominic-Giampa...

53- http://www.amazon.com/File-Systems-Structures-Thomas-Harbron...

54- ...well, I'll stop here.

Of course, the equivalent knowledge can be obtained by trial-and-error, which would take longer and might result in costly errors and imperfect design. The greater danger here is that a sole developer, without the feedback and interaction of even a small group of capable and experienced programmers could simply burn a lot of time repeating the mistakes made by those who have already trenched that territory.

If the goal is to write a small RTOS on a small but nicely-featured microcontroller, then the C books and the uC/OS book might be a good shove in the right direction. Things start getting complicated if you need to write such things as a full USB stack, PCIe subsystem, graphics drivers, etc.

I'm currently reading The Design of the UNIX Operating System [0], so this is super interesting for me to watch. I love how he creates a spellchecking program live, while being filmed.

[0]

Anyone who has ever written a small RTOS on a small 8 bit embedded processor will only laugh at the OP. And, I hate to say, it would be justified. There are about twenty or thirty books between where he is now and where he'd have to be in order to even start talking about designing an OS for a desktop platform. Add to that 10,000 hours of coding low to high-level projects across embedded to desktop platforms.

A quick read of the "About" page is probably in order:

http://gusc.lv/about/

What to say?

"Someone holding a cat by the tail learns something he can learn in no other way" --Mark Twain.

Here's the tip of the tail:

http://www.amazon.com/Embedded-Controller-Forth-8051-Family/...

http://www.amazon.com/Operating-System-Concepts-Abraham-Silb...

http://www.amazon.com/Performance-Preemptive-Multitasking-Mi...

http://www.amazon.com/Design-Operating-System-Prentice-Hall-...

Have fun.