10

INPUT/OUTPUT

One of the most underemphasized topics

in many university programming courses

is input/output (I/O). I/O plays a central

role in most real-world applications of comput-

ers. Just consider an ATM cash machine, which uses

multiple I/O operations for both input—reading your

card and reading your typed-in cash request—and

output—printing instructions on the screen, printing

your receipt, and most important, controlling the

machine to output your money!

R is not the tool you would choose for running an ATM, but it features
a highly versatile array of I/O capabilities, as you will learn in this chapter.
We’ll start with the basics of access to the keyboard and monitor, and then
go into considerable detail on reading and writing files, including the nav-
igation of file directories. Finally, we discuss R’s facilities for accessing the
Internet.