These notes are written based on the book The C Programming Language, by Brian Kernighan and Dennis Ritchie, or K&R (The second edition was published in 1988 by Prentice-Hall, ISBN 0-13-110362-8.). The sections are cross-referenced to those of K&R, for the reader who wants to pursue a more in-depth exposition. | Text data files, it must be admitted, are not always as compact or as efficient to read and write as binary files. It can be a bit more work to set up the code which reads and writes them. But they have some powerful advantages: any time you need to, you can look at them using ordinary text editors and other tools. If program A is writing a data file which program B is supposed to be able to read but cannot, you can immediately look at the file to see if it's in the correct format and so determine whether it's program A's or B's fault. If program A has not been written yet, you can easily create a data file by hand to test program B with. Text files are automatically portable between machines, even those where integers and other data types are of different sizes or are laid out differently in memory. Because they're not expected to have the rigid formats of binary files, it tends to be more natural to arrange text files so that as the data file format changes slightly, newer (or older) versions of the software can read older (or newer) versions of the data file. Text data files are the focus of this chapter; they're what I use all the time, and they're what I recommend you use unless you have compelling reasons not to.
