%Revision
%Thadeu Cascardo

# Hardware

# Machine types

* Von Neumman and the stored program
* Accumulator
* Stack
* Registers
* ISA
* Data, addresses and control registers

# Memory

* Buses
* Memory Cache
* Segmentation
* Paging and Virtual Memory
* Operation Reordering

# Interrupts

* Register saving
* Different stack and context
* Must enable, disable, ack

# Supervisor mode

* Protected instructions
* Protected registers
* Traps

# Multi-processor systems

* SMP
* NUMA
* Memory coherency

# I/O

* Buses
* Different address space
* Memory mapped registers
* Device memory
* Shared memory
* DMA

# Operating System

# Extended machine

* Software layer providing abstraction
* Examples:
	- Filesystem instead of disk drive
	- Virtual memory and transparent swap instead of overlays

# Resources Manager

* CPU Manager
* Memory Manager
* Devices Manager

# Process Management

* Scheduling
* Concurrency
* Inter-process communication

# Memory Management

* Virtual Memory
* Memory allocation
* Memory hierarchy ("secondary" memory or storage)

# I/O

* Access protection
* Sharing
* Abstraction

# Others

* Filesystem
* Network

# Mechanism and policy

* Provide mechanism in kernel space
* Allow policy to user space

# Unix, GNU, Linux and POSIX

# History

* MULTICS
* Ken Thompson and Unix
* Dennis Ritchie and C language
* Berkeley Unix
* Unix Wars
* RMS and GNU Project
* Minix
* Linux and GNU

# Architecture

* toolchain: GNU
* kernel: Linux
* libc: GNU libc
* loader: GNU
* shell: GNU bash
* utils: GNU coreutils
* System: GNU + Linux
* Other systems: *BSD, OpenSolaris, etc

# Systems using Linux

* toolchain is always GNU
	- Intel CC and tcc build Linux, but their use is unknown
* libc: uclibc, dietlibc, eglibc, others...
* busybox

# GNU systems

* Most systems are GNU + Linux
* GNU Hurd
* Debian GNU/kFreeBSD

# Standards

* man standards
* Unix V7
* 4.[234]BSD
* System V
* SVr[234]
* C
* POSIX
* XPG
* SUS

# Free software

# Intellectual Rights

* Copyright
* "Author right"
* Patents
* Trademark
* Trade Secret

# RMS and FSF

* The GNU Manifesto
* Free Software Foundation
* Copyleft

# Copyleft

* Public Domain allows changes to be non-free
* The author may give permissions through licenses
* The license may request conditions on distribution
* A copyleft license requires the work to be kept free
* The GPL

# GPL version 2

* Allows use
* Allows source code redistribution, including a fee
* Allows modifications and their distribution on the condition that they are
  marked as so and licensed as GPL too
* Allows distribution of binaries, when source code access is still possible
* Does not allow further restrictions

# Myths

* The GPL requires the software to be free as in "free beer" - FALSE
* The GPL requires modifications to be published - FALSE
* The GPL requires all my code to be GPL - FALSE

# License compatibility

* All requirements must be satisfied simultaneously
* The GPL does not allow further requirements
* You can only combine GPL code with code licensed with no restrictions besides
  those in the GPL