Review of C Programming on Unix
C problems are often due to misunderstanding the computer
	Most complaints I hear about C are not about C
	Most arguments I hear against C are "x detail should be hidden from programmers"

Tools:
	man
	gcc
	gdb
	vim/emacs/nano/pico/gedit/whatever
	make
	git

C versions:
	C99-style "for" loop
	Nested functions and GNU C
	Older conventions are still around
	Has not changed as much as C++

Memory, virtual memory, and organization
	It's a review, but CS253 was a while ago
	Continuous 64-bit block of addresses
	Segments:  Stack, Heap, Code
	Shall we print an address from each?
	In the kernel, these rules *mostly* apply
		- Stack can be very limited in the kernel
		- Kernel dynamic memory must be managed carefully
	Address alignment and performance
		- Can turn this off

Pointers:
	Pointers are 64-bit unsigned integers
	Pointers can point to any type, since it's just a number
	Use size_t for data structure sizes
	ssize_t for signed size_t (why is this ok?)
	sizeof returns the size of variables
	Pointer arithmatic example:  Iteration
		- Example:  Sum of an array
		- Example:  Encrypt a string with shift of 13 (if time permits)
		- Example:  Square each number in an array
		- Incrementation amount determined by type
		- Either direction is possible
	void* can point to anything!
	Programs can write to anywhere they're allowed to write to
		- Example:  Change a different variable
	Passing pointers to functions:  Sort of a manual pass-by-reference

Allocating Memory:
	malloc and free
	calloc
	Don't forget to deallocate!
	Arrays vs. Python lists, and realloc
		- Userspace:  C++ vector
		- Kernel:  Kernel linked lists

goto:
	Actually used a lot in the kernel
	Example:  How often?
	Considered harmful
		- Which is harmful

Pointers to functions:
	CS253 reminder:  We used these with pthreads, and probably other places
	Now we will do things that are more silly!
		An array of pointers to word-scrambling functions
		A function that takes a list of functions to apply to a word
		A function that returns a function?  get_scrambler
	Ok, that was silly, but how about something that actually happens?

Structs with function pointers:
	Kind of like an object
	We will actually have to make these when we put files in /proc
	Project 1:  Make one and hand it to the test function
	An example that was in 253:  sigaction
		We'll make a program that handles ctrl+c again
 
Resources:
	A guide to GDB:   http://beej.us/guide/bggdb/
	Make (Wikipedia): http://en.wikipedia.org/wiki/Make_(software)
	Pointer arithmatic overview:  http://www.cs.umd.edu/class/sum2003/cmsc311/Notes/BitOp/pointer.html
	Pointers (Wikipedia): http://en.wikipedia.org/wiki/Pointer_(computer_programming)