1.3. What is a Program?¶
A program is a sequence of instructions that specifies how to perform a computation. The computation might be something mathematical, like solving a system of equations or finding the roots of a polynomial, but it can also be a symbolic computation, like searching and replacing text in a document or (strangely enough) compiling a program.
The instructions (or commands, or statements) look different in different programming languages, but there are a few basic functions that appear in just about every language:
 input:
Get data from the keyboard, or 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.
 testing:
Check for certain conditions and execute the appropriate sequence of statements.
 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 functions that look more or less like these. Thus, one way to describe programming is the process of breaking a large, complex task up into smaller and smaller subtasks until eventually the subtasks are simple enough to be performed with one of these simple functions.
Q1: A(n) is a series of instructions that are used to perform a computation.

Q2: Match each term to an example of it.
Try again!
 input
 the program user enters a few ordered pairs when prompted in the terminal
 output
 the calculated distances are saved to a file
 math
 the program calculates the distance between two ordered pairs
 testing
 the program makes sure that the calculated distance is nonnegative
 repetition
 the program continues executing as long as there are more data points to compute distance