Unicon Book

Chapter 1
Programs and Expressions
This chapter presents many of the key features of Unicon, starting with those it has in
common with other popular languages. Detailed instructions show how to compile and run
programs. Soon the examples introduce important ways in which Unicon is different from
other languages. These differences are more than skin deep. If you dig deeply, you can find
dozens of details where Unicon provides just the right blend of simplicity, flexibility, and
power. After this chapter, you will know how to
• edit, compile, and execute Unicon programs
• use the basic types to perform calculations
• identify expressions that can fail, or produce multiple results
• control the flow of execution using conditionals, looping, and procedures
1.1 Your First Unicon Program
This section presents the nuts and bolts of writing and running an Unicon program, after
which you will be able to try the code examples or write your own programs. Before you
can run the examples here or in any subsequent chapter, you must install Unicon on your
system. (See Appendix F for details on downloading and installing Unicon from the Unicon
web site, http://unicon.org.) We are going to be very explicit here, and assume nothing
about your background. If you are an experienced programmer, you will want to skim this
section, and move on to the next section. If you are completely new to programming, have
no fear. Unicon is pretty easy to learn.
All programs consist of commands that use hardware to obtain or present information
to users, and perform calculations that transform information into a more useful form.
To program a computer you write a document containing instructions for the computer to
carry out. In Unicon a list of instructions is called a procedure, and a program is a collection
of one or more procedures. In larger programs, groups of related procedures are organized
7