A program is
a sequence of instructions that specifies how to perform a computation. The computation might be something mathematical, such as solving a system of
equations or finding the roots of a polynomial, but it can also be a symbolic
computation, such as searching and replacing text in a document or (strangely
enough) compiling a program.
The details
look different in different languages, but a few basic instructions appear in
just about every language:
Input: Get data from the keyboard, a file, or some other
device.
Output: Display data on the screen or send data to a file or
other device.
Math: Perform basic mathematical operations like addition
and multiplication.
Conditional execution: Check for certain
conditions and execute the appropriate code.
Repetition: Perform some action repeatedly, usually with some
variation.
Believe it or not, that’s pretty much all there is to it. Every program you’ve ever used,
No matter how
complicated, is made up of instructions that look pretty much like these.
So you can
think of programming as the process of breaking a large, complex task into
smaller and
smaller subtasks until the subtasks are simple enough to be performed with
one of these
basic instructions.
That may be a little
vague, but we will come back to this topic when we talk about algorithms.
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