Let's work with files a bit!
	Can we open a file and print out the middle third?
	open
	lseek
	read
	close

Note that there are two familes of functions available!  Equivalents:
	Unix		stdio
	open		fopen
	close		fclose
	lseek		fseek
	read		fread
	write		fwrite
	fstat		None (platform-specific)
	
So which one do I use?
	For CS253:  unix
	If you're sure your program runs only on unix:  Doesn't really matter
	If your code needs to run on Windows:  stdio

Unix file descriptors:
	Could describe other stuff, like pipes and network sockets
	So you need to get used to using these
	That's why we'll use them for CS253

Another way:  mmap
	In case you want to just pretend the file is already in memory
	A funny use case:  Reading a file into a C++ string
	
C++ and C integration:
	A lot of C++ libraries build on top of C
	Let's write a library function that might be useful!
	readlines(filename), returns an STL vector of strings
	We can use the C++ string constructor's size limit parameter