You may already have used software, perhaps for word processing or spreadsheets, to solve problems. Perhaps now you are curious to learn how programmers write software. A program is a set of step-by-step instructions that directs the computer to do the tasks you want it to do and produce the results you want.
There are at least three good reasons for learning programming:
- Programming helps you understand computers. The computer is only a tool. If you learn how to write simple programs, you will gain more knowledge about how a computer works.
- Writing a few simple programs increases your confidence level. Many people find great personal satisfaction in creating a set of instructions that solve a problem.
- Learning programming lets you find out quickly whether you like programming and whether you have the analytical turn of mind programmers need. Even if you decide that programming is not for you, understanding the process certainly will increase your appreciation of what programmers and computers can do.
A set of rules that provides a way of telling a computer what operations to perform is called a programming language. There is not, however, just one programming language; there are many. In this chapter you will learn about controlling a computer through the process of programming. You may even discover that you might want to become a programmer.
An important point before we proceed: You will not be a programmer when you finish reading this chapter or even when you finish reading the final chapter. Programming proficiency takes practice and training beyond the scope of this book. However, you will become acquainted with how programmers develop solutions to a variety of problems.
In general, the programmer's job is to convert problem solutions into instructions for the computer. That is, the programmer prepares the instructions of a computer program and runs those instructions on the computer, tests the program to see if it is working properly, and makes corrections to the program. The programmer also writes a report on the program. These activities are all done for the purpose of helping a user fill a need, such as paying employees, billing customers, or admitting students to college.
The programming activities just described could be done, perhaps, as solo activities, but a programmer typically interacts with a variety of people. For example, if a program is part of a system of several programs, the programmer coordinates with other programmers to make sure that the programs fit together well. If you were a programmer, you might also have coordination meetings with users, managers, systems analysts, and with peers who evaluate your work-just as you evaluate theirs.
Let us turn to the programming process.
Developing a program involves steps similar to any problem-solving task. There are five main ingredients in the programming process:
- Defining the problem
- Planning the solution
- Coding the program
- Testing the program
- Documenting the program
Let us discuss each of these in turn.
- Defining the Problem
- Planning the Solution
- Coding the Program
- Testing the Program
- Desk-checking. This phase, similar to proofreading, is sometimes avoided by the programmer who is looking for a shortcut and is eager to run the program on the computer once it is written. However, with careful desk-checking you may discover several errors and possibly save yourself time in the long run. In desk-checking you simply sit down and mentally trace, or check, the logic of the program to attempt to ensure that it is error-free and workable. Many organizations take this phase a step further with a walkthrough, a process in which a group of programmers-your peers-review your program and offer suggestions in a collegial way.
- Translating. A translator is a program that (1) checks the
syntax of your program to make sure the programming language was used
correctly, giving you all the syntax-error messages, called diagnostics,
and (2) then translates your program into a form the computer can
understand. A by-product of the process is that the translator tells you
if you have improperly used the programming language in some way. These
types of mistakes are called syntax errors. The translator produces
descriptive error messages. For instance, if in FORTRAN you mistakenly
write N=2 *(I+J))-which has two closing parentheses instead of one-you
will get a message that says, "UNMATCHED PARENTHESES." (Different
translators may provide different wording for error messages.) Programs
are most commonly translated by a compiler. A compiler translates
your entire program at one time. The translation involves your original
program, called a source module, which is transformed by a compiler into
an object module. Prewritten programs from a system library may be added
during the link/load phase, which results in a load module. The load
module can then be executed by the computer.
- Debugging. A term used extensively in programming, debugging means detecting, locating, and correcting bugs (mistakes), usually by running the program. These bugs are logic errors, such as telling a computer to repeat an operation but not telling it how to stop repeating. In this phase you run the program using test data that you devise. You must plan the test data carefully to make sure you test every part of the program.
- Documenting the Program
Suppose that, as a programmer, you are contacted because your services are needed. You meet with users from the client organization to analyze the problem, or you meet with a systems analyst who outlines the project. Specifically, the task of defining the problem consists of identifying what it is you know (input-given data), and what it is you want to obtain (output-the result). Eventually, you produce a written agreement that, among other things, specifies the kind of input, processing, and output required. This is not a simple process.
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Pseudocode is an English-like nonstandard language that lets you state your solution with more precision than you can in plain English but with less precision than is required when using a formal programming language. Pseudocode permits you to focus on the program logic without having to be concerned just yet about the precise syntax of a particular programming language. However, pseudocode is not executable on the computer. We will illustrate these later in this chapter, when we focus on language examples.
As the programmer, your next step is to code the program-that is, to express your solution in a programming language. You will translate the logic from the flowchart or pseudocode-or some other tool-to a programming language. As we have already noted, a programming language is a set of rules that provides a way of instructing the computer what operations to perform. There are many programming languages: BASIC, COBOL, Pascal, FORTRAN, and C are some examples. You may find yourself working with one or more of these. We will discuss the different types of languages in detail later in this chapter.
Although programming languages operate grammatically, somewhat like the English language, they are much more precise. To get your program to work, you have to follow exactly the rules-the syntax-of the language you are using. Of course, using the language correctly is no guarantee that your program will work, any more than speaking grammatically correct English means you know what you are talking about. The point is that correct use of the language is the required first step. Then your coded program must be keyed, probably using a terminal or personal computer, in a form the computer can understand.
One more note here: Programmers usually use a text editor, which is somewhat like a word processing program, to create a file that contains the program. However, as a beginner, you will probably want to write your program code on paper first.
Some experts insist that a well-designed program can be written correctly the first time. In fact, they assert that there are mathematical ways to prove that a program is correct. However, the imperfections of the world are still with us, so most programmers get used to the idea that their newly written programs probably have a few errors. This is a bit discouraging at first, since programmers tend to be precise, careful, detail-oriented people who take pride in their work. Still, there are many opportunities to introduce mistakes into programs, and you, just as those who have gone before you, will probably find several of them.
Eventually, after coding the program, you must prepare to test it on the computer. This step involves these phases:
Documenting is an ongoing, necessary process, although, as many programmers are, you may be eager to pursue more exciting computer-centered activities. Documentation is a written detailed description of the programming cycle and specific facts about the program. Typical program documentation materials include the origin and nature of the problem, a brief narrative description of the program, logic tools such as flowcharts and pseudocode, data-record descriptions, program listings, and testing results. Comments in the program itself are also considered an essential part of documentation. Many programmers document as they code. In a broader sense, program documentation can be part of the documentation for an entire system.
The wise programmer continues to document the program throughout its design, development, and testing. Documentation is needed to supplement human memory and to help organize program planning. Also, documentation is critical to communicate with others who have an interest in the program, especially other programmers who may be part of a programming team. And, since turnover is high in the computer industry, written documentation is needed so that those who come after you can make any necessary modifications in the program or track down any errors that you missed.
There is a shortage of qualified personnel in the computer field. Before you join their ranks, consider the advantages of the computer field and what it takes to succeed in it.
The Joys of the Field
Although many people make career changes into the computer field, few choose to leave it. In fact, surveys of computer professionals, especially programmers, consistently report a high level of job satisfaction. There are several reasons for this contentment. One is the challenge-most jobs in the computer industry are not routine. Another is security, since established computer professionals can usually find work. And that work pays well-you will probably not be rich, but you should be comfortable. The computer industry has historically been a rewarding place for women and minorities. And, finally, the industry holds endless fascination since it is always changing.
What It Takes
You need, of course, some credentials, most often a two- or four-year degree in computer information systems or computer science. The requirements and salaries vary by the organization and the region, so we will not dwell on these here. Beyond that, the person most likely to land a job and move up the career ladder is the one with excellent communication skills, both oral and written . These are also the qualities that can be observed by potential employers in an interview. Promotions are sometimes tied to advanced degrees (an M.B.A. or an M.S. in computer science).
Open Doors
The overall outlook for the computer field is promising. The Bureau of Labor Statistics shows, through the year 2010, a 72 percent increase in programmers and a 69 percent increase in system use today, and we will discuss the most popular ones later In the chapter. Before we turn to specific languages, however, we need to discuss levels of language.