Thoughts on C Programming for Audio
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Four types of programs, based on the different possible combinations of "file I/O" and "stream I/O":
	Record: access input stream from the ADC, write it to a file
	Play: read from an audio file, send it as a stream to the DAC
	Process: in real time, access ADC and DAC, modify data in between
	Hack: in non-real time, access file, modify data, output to file
	(Combinations, modify while recording, add effects while playing, etc.)

File reading (in C, not using PortAudio):
	Declare a file pointer
	Assign it to an existing file (get filename from command-line argument, or query to user, or command from user; limit user's choices if possible/appropriate)
	Make sure file exists; report error if there's a problem finding it
	Open the file (with fopen()); report an error if there's a problem opening it
	Sniff header; (report an error if it's not the right kind of file); determine file format, sample rate, channels, data format, length of file
	Allocate buffer memory for the samples you're going to want to read in
	Read in data,  possibly within a 'for' loop that checks for end-of-file or some other stop cue
	Do something with the data

File writing (in C, not using PortAudio):
	Declare a file pointer
	Assign it to a directory/filename (get filename from command-line argument, or query to user, or command from user; limit user's choices if possible/appropriate)
	Open the file (with fopen()); report an error if there's a problem opening it
	Write header -- file format, sample rate, channels, data format, length of file, etc.
	Open stream and read data, and/or put data into an array
	Do something with it (optional)
	Write data (from an input stream, or from an array or buffer you've created)
	Close file
	Wait for more instructions or quit

Streaming audio from ADC and/or to DAC:
	Declare and define a data structure ('userData') for necessary ongoing data
	Declare and define a callback function
	In main function:
		Initialize and start audio stream
		Use an event loop to look for stopping command or other crucial event
		Modify userData as necessary for continuous control
		Clean up, wait for more instructions or quit