- Why Programming?
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.
- What Programmers Do
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
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.
- 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
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.
- Planning the Solution
Two common ways of planning the solution to a problem are to draw a
flowchart and to write pseudocode, or possibly both. Essentially, a flowchart
is a pictorial representation of a step-by-step solution to a problem.
It consists of arrows representing the direction the program takes and
boxes and other symbols representing actions. It is a map of what your
program is going to do and how it is going to do it. The American
National Standards Institute (ANSI) has developed a standard set of flowchart
symbols. Figure 1 shows the symbols and how they might be used
in a simple flowchart of a common everyday act-preparing a letter for
Figure 1: Flow Chart Symbols and Flow Chart For Mailing Letter
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
- Coding the Program
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.
- Testing the Program
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:
- 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
Documenting the Program
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.
Programming as a Career
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
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).
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.
Levels of Language
Programming languages are said to be "lower" or "higher," depending on
how close they are to the language the computer itself uses (Os and 1s = low)
or to the language people use (more English-like-high). We will consider
five levels of language. They are numbered 1 through 5 to correspond
to levels, or generations. In terms of ease of use and capabilities, each
generation is an improvement over its predecessors. The five generations of
- Machine language
- Assembly languages
- High-level languages
- Very high-level languages
- Natural languages
look at each of these categories.
Humans do not like to deal in numbers alone-they prefer letters and
words. But, strictly speaking, numbers are what machine language is. This
lowest level of language, machine language, represents data and program
instructions as 1s and Os-binary digits corresponding to the on and off
electrical states in the computer.
Each type of computer has its
own machine language. In the early days of computing, programmers had
rudimentary systems for combining numbers to represent instructions such
as add and compare. Primitive by today's standards, the programs were
not convenient for people to read and use. The computer industry quickly
moved to develop assembly languages.
Today, assembly languages are considered very low level-that is, they are
not as convenient for people to use as more recent languages. At the time
they were developed, however, they were considered a great leap forward.
To replace the Is and Os used in machine language, assembly languages use
mnemonic codes, abbreviations that are easy to remember: A for Add, C
for Compare, MP for Multiply, STO for storing information in memory,
and so on. Although these codes are not English words, they are still-
from the standpoint of human convenience-preferable to numbers (Os
and 1s) alone. Furthermore, assembly languages permit the use of names-
perhaps RATE or TOTAL-for memory locations instead of actual
address numbers. just like machine language, each type of computer has
its own assembly language.
Figure 2: Example Assembly Language Program
The programmer who uses an assembly language requires a translator
to convert the assembly language program into machine language. A translator
is needed because machine language is the only language the computer
can actually execute. The translator is an assembler program, also
referred to as an assembler. It takes the programs written in assembly language
and turns them into machine language. Programmers need not
worry about the translating aspect; they need only write programs in
assembly language. The translation is taken care of by the assembler.
Although assembly languages represent a step forward, they still have
many disadvantages. A key disadvantage is that assembly language is
detailed in the extreme, making assembly programming repetitive, tedious,
and error prone. This drawback is apparent in the program in Figure 2.
Assembly language may be easier to read than machine language, but it is
The first widespread use of high-level languages in the early 1960s transformed
programming into something quite different from what it had
been. Programs were written in an English-like manner, thus making them
more convenient to use. As a result, a programmer could accomplish more
with less effort, and programs could now direct much more complex tasks.
These so-called third-generation languages spurred the great increase in
data processing that characterized the 1960s and 1970s. During that time
the number of mainframes in use increased from hundreds to tens of thousands.
The impact of third-generation languages on our society has been enormous.
Of course, a translator is needed to translate the symbolic statements of
a high-level language into computer-executable machine language; this
translator is usually a compiler. There are many compilers for each language
and one for each type of computer. Since the machine language generated
by one computer's COBOL compiler, for instance, is not the
machine language of some other computer, it is necessary to have a
COBOL compiler for each type of computer on which COBOL programs
are to be run. Keep in mind, however, that even though a given program
would be compiled to different machine language versions on different
machines, the source program itself-the COBOL version-can be essentially
identical on each machine.
Some languages are created to serve a specific purpose, such as controlling
industrial robots or creating graphics. Many languages, however, are
extraordinarily flexible and are considered to be general-purpose. In the
past the majority of programming applications were written in BASIC,
FORTRAN, or COBOL-all general-purpose languages. In addition to
these three, another popular high-level language is C, which we will discuss
Very High-Level Languages
Languages called very high-level languages are often known by their generation
number, that is, they are called fourth-generation languages or, more
Will the real fourth-generation languages please stand up? There is no
consensus about what constitutes a fourth-generation language. The 4GLs are
essentially shorthand programming languages. An operation that requires
hundreds of lines in a third-generation language such as COBOL typically
requires only five to ten lines in a 4GL. However, beyond the basic criterion
of conciseness, 4GLs are difficult to describe.
Fourth-generation languages share some characteristics. The first is that
they make a true break with the prior generation-they are basically non-procedural.
A procedural language tells the computer how a task is done:
Add this, compare that, do this if something is true, and so forth-a very
specific step-by-step process. The first three generations of languages are
all procedural. In a nonprocedural language, the concept changes. Here,
users define only what they want the computer to do; the user does not
provide the details of just how it is to be done. Obviously, it is a lot easier
and faster just to say what you want rather than how to get it. This leads
us to the issue of productivity, a key characteristic of fourth-generation
Folklore has it that fourth-generation languages can improve productivity
by a factor of 5 to 50. The folklore is true. Most experts say the average
improvement factor is about 10-that is, you can be ten times more productive
in a fourth-generation language than in a third-generation language.
Consider this request: Produce a report showing the total units sold
for each product, by customer, in each month and year, and with a subtotal
for each customer. In addition, each new customer must start on a new
page. A 4GL request looks something like this:
TABLE FILE SALES
SUM UNITS BY MONTH BY CUSTOMER BY PRODUCT
ON CUSTOMER SUBTOTAL PAGE BREAK
Even though some training is required to do even this much, you can see
that it is pretty simple. The third-generation language COBOL, however,
typically requires over 500 statements to fulfill the same request. If we
define productivity as producing equivalent results in less time, then
fourth-generation languages clearly increase productivity.
Fourth-generation languages are not all peaches and cream and productivity.
The 4GLs are still evolving, and that which is still evolving cannot be
fully defined or standardized. What is more, since many 4GLs are easy to
use, they attract a large number of new users, who may then overcrowd
the computer system. One of the main criticisms is that the new languages
lack the necessary control and flexibility when it comes to planning how
you want the output to look. A common perception of 4GLs is that they
do not make efficient use of machine resources; however, the benefits of
getting a program finished more quickly can far outweigh the extra costs
of running it.
Fourth-generation languages are beneficial because
- They are results-oriented; they emphasize what instead of how.
- They improve productivity because programs are easy to write and
- They can be used with a minimum of training by both programmers
- They shield users from needing an awareness of hardware and program
It was not long ago that few people believed that 4GLs would ever be able
to replace third-generation languages. These 4GL languages are being
used, but in a very limited way.
A variation on fourth-generation languages are query languages, which
can be used to retrieve information from databases. Data is usually added
to databases according to a plan, and planned reports may also be produced.
But what about a user who needs an unscheduled report or a report
that differs somehow from the standard reports? A user can learn a query
language fairly easily and then be able to input a request and receive the
resulting report right on his or her own terminal or personal computer. A
standardized query language, which can be used with several different
commercial database programs, is Structured Query Language, popularly
known as SQL. Other popular query languages are Query-by-Example,
known as QBE, and Intellect.
The word "natural" has become almost as popular in computing circles as it
has in the supermarket. Fifth-generation languages are, as you may guess,
even more ill-defined than fourth-generation languages. They are most
often called natural languages because of their resemblance to the "natural"
spoken English language. And, to the manager new to computers for
whom these languages are now aimed, natural means human-like. Instead
of being forced to key correct commands and data names in correct order,
a manager tells the computer what to do by keying in his or her own words.
A manager can say the same thing any number of ways. For example,
"Get me tennis racket sales for January" works just as well as "I want
January tennis racket revenues." Such a request may contain misspelled
words, lack articles and verbs, and even use slang. The natural language
translates human instructions-bad grammar, slang, and all-into code
the computer understands. If it is not sure what the user has in mind, it
politely asks for further explanation.
Figure 3: Example of Natural Language Interaction
Natural languages are sometimes referred to as knowledge-based languages,
because natural languages are used to interact with a base of
knowledge on some subject. The use of a natural language to access a
knowledge base is called a knowledge-based system.
Consider this request that could be given in the 4GL Focus:
"SUM ORDERS BY DATE BY REGION." If we alter the request and, still in
Focus, say something like "Give me the dates and the regions after you've
added up the orders," the computer will spit back the user-friendly version
of "You've got to be kidding" and give up. But some natural languages can
handle such a request. Users can relax the structure of their requests and
increase the freedom of their interaction with the data.
Here is a typical natural language request:
REPORT THE BASE SALARY, COMMISSIONS AND YEARS OF
SERVICE BROKEN DOWN BY STATE AND CITY FOR SALESCLERKS
IN NEW JERSEY AND MASSACHUSETTS.
You can hardly get closer to conversational English than that.
An example of a natural language is shown in Figure 3. Natural languages
excel at easy data access. Indeed, the most common application for
natural languages is interacting with databases.
Choosing a Language
How do you choose the language with which to write your program?
There are several possibilities:
- In a work environment, your manager may decree that everyone on
your project will use a certain language.
- You may use a certain language, particularly in a business environment,
based on the need to interface with other programs; if two programs are
to work together, it is easiest if they are written in the same language.
- You may choose a language based on its suitability for the task. For
example, a business program that handles large files may be best written
in the business language COBOL.
- If a program is to be run on different computers, it must be written in a
language that is portable-suitable on each type of computer-so that
the program need be written only once.
- You may be limited by the availability of the language. Not all languages
are available in all installations or on all computers.
- The language may be limited to the expertise of the programmer; that
is, the program may have to be written in a language the available programmer
- Perhaps the simplest reason, one that applies to many amateur
programmers, is that they know the language called BASIC because it came
with-or was inexpensively purchased with-their personal computers.
Major Programming Languages
The following sections on individual languages will give you an overview
of the third-generation languages in common use today: FORTRAN (a scientific language),
COBOL (a business language), BASIC (simple language used for education and business), Pascal (education), Ada (military), and C (general purposed).
Figure 4: Flow Chart For Averaging Numbers
This chapter will present programs written in some of these languages. You
will also see output produced by each program. Each program is designed
to find the average of three numbers; the resulting average is shown in the
sample output matching each program. Since all programs perform the
same task, you will see some of the differences and similarities among the
languages. We do not expect you to understand these programs; they are
here merely to let you glimpse each language. Figure 4 presents the flowchart
and pseudocode for the task of averaging numbers. As we discuss
each language, we will provide a program for averaging numbers that follows
the logic shown in this figure.
FORTRAN: The First High-Level Language
Developed by IBM and introduced in 1954, FORTRAN-for FORmula
TRANslator-was the first high-level language. FORTRAN is a scientifically
oriented language-in the early days use of the computer was primarily
associated with engineering, mathematical, and scientific research tasks.
Figure 5: Example Fortran Program To Average Numbers
FORTRAN is noted for its brevity, and this characteristic is part of the
reason why it remains popular. This language is very good at serving its
primary purpose, which is execution of complex formulas such as those
used in economic analysis and engineering. Although in the past it was
considered limited in regard to file processing or data processing, its capabilities
have been greatly improved.
Not all programs are organized in the same way. Organization varies
according to the language used. In many languages (such as COBOL), programs
are divided into a series of parts. FORTRAN programs are not
composed of different parts (although it is possible to link FORTRAN
programs together); a FORTRAN program consists of statements one
after the other. Different types of data are identified as the data is used.
Descriptions for data records appear in format statements that accompany
the READ and WRITE statements. Figure 5 shows a FORTRAN program
and a sample output from the program.
COBOL: The Language of Business
In the 1950s FORTRAN had been developed, but there was still no
accepted high-level programming language appropriate for business. The
U.S. Department of Defense in particular was interested in creating such
a standardized language, and so it called together representatives from
government and various industries, including the computer industry. These
representatives formed CODASYL-COnference of DAta SYstem Languages.
In 1959 CODASYL introduced COBOL-for COmmon BusinessOriented Language.
Figure 6: Example COBOL Program to Average Numbers
The U.S. government offered encouragement by insisting that anyone
attempting to win government contracts for computer-related projects had
to use COBOL. The American National Standards Institute first standardized
COBOL in 1968 and, in 1974, issued standards for another version
known as ANSI-COBOL. After more than seven controversial years of
industry debate, the standard known as COBOL 85 was approved, making
COBOL a more usable modern-day software tool. The principal benefit of
standardization is that COBOL is relatively machine independent-
that is, a program written for one type of computer can be run with only
slight modifications on another type for which a COBOL compiler has
COBOL is very good for processing large files and performing relatively
simple business calculations, such as payroll or interest. A noteworthy feature
of COBOL is that it is English-like-far more so than FORTRAN or
BASIC. The variable names are set up in such a way that, even if you know
nothing about programming, you can still understand what the program
does. For example:
IF SALES-AMOUNT IS GREATER THAN SALES-QUOTA
COMPUTE COMMISSION = MAX-RATE * SALES-AMOUNT
COMPUTE COMMISSION = MIN-RATE * SALES-AMOUNT.
Once you understand programming principles, it is not too difficult to
add COBOL to your repertoire. COBOL can be used for just about any
task related to business programming; indeed, it is especially suited to
processing alphanumeric data such as street addresses, purchased items, and
dollar amounts-the data of business. However, the feature that makes
COBOL so useful-its English-like appearance and easy readability-is
also a weakness because a COBOL program can be incredibly verbose. A
programmer seldom knocks out a quick COBOL program. In fact, there is
hardly such a thing as a quick COBOL program; there are just too many
program lines to write, even to accomplish a simple task. For speed and
simplicity, BASIC, FORTRAN, and Pascal are probably better bets.
As you can see in Figure 6, a COBOL program is divided into four
parts called divisions. The identification division identifies the program by
name and often contains helpful comments as well. The environment division
describes the computer on which the program will be compiled and
executed. It also relates each file of the program to the specific physical
device, such as the tape drive or printer, that will read or write the file. The
data division contains details about the data processed by the program,
such as type of characters (whether numeric or alphanumeric), number of
characters, and placement of decimal points. The procedure division
contains the statements that give the computer specific instructions to carry
out the logic of the program.
It has been fashionable for some time to criticize COBOL: It is old-fashioned,
cumbersome, and inelegant. In fact, some companies, devoted
to fast, nimble program development, are converting to the more trendy
language C. But COBOL, with more than 30 years of staying power, is still
famous for its clear code, which is easy to read and debug.
BASIC: For Beginners and Others
BASIC-Beginners' All-purpose Symbolic Instruction Code-is a common
language that is easy to learn. Developed at Dartmouth College, BASIC
was introduced by John Kemeny and Thomas Kurtz in 1965 and was originally
intended for use by students in an academic environment. In the late
1960s it became widely used in interactive time-sharing environments in
universities and colleges. The use of BASIC has extended to business and
personal computer systems.
Figure 7: Example Basic Program to Average Numbers
The primary feature of BASIC is one that may be of interest to many
readers of this book: BASIC is easy to learn, even for a person who has
never programmed before. Thus, the language is used often to train students
in the classroom. BASIC is also used by non-programming people,
such as engineers, who find it useful in problem solving. For many years,
BASIC was looked down on by "real programmers," who complained that
it had too many limitations and was not suitable for complex tasks. Newer
versions, such as Microsoft's QuickBASIC, include substantial improvements.
An example of a BASIC program and its output are shown in Figure 7.
Pascal: The Language of Simplicity
Named for Blaise Pascal, the seventeenth-century French mathematician,
Pascal was developed as a teaching language by a Swiss computer scientist,
Niklaus Wirth, and first became available in 1971. Since that time it has
become quite popular, first in Europe and now in the United States, particularly
in universities and colleges offering computer science programs.
The foremost feature of Pascal is that it is simpler than other languages
-it has fewer features and is less wordy than most. In addition to the popularity
of Pascal in college computer science departments, the language has
also made large inroads in the personal computer market as a simple yet
sophisticated alternative to BASIC. Over the years new versions have
improved on the original capabilities of Pascal. Today, Borland's Turbo
Pascal leads the Pascal world because its designers eliminated most of the
drawbacks of the original Pascal. Turbo Pascal is used by the business
community and is often the choice of nonprofessional programmers who
need to write their own programs.
Ada: Named for the Countess
Is any software worth over $25 billion? Not any more, according to
Defense Department experts. In 1974 the U.S. Department of Defense had
spent that amount on all kinds of software for a hodgepodge of languages
for its needs. The answer to this problem turned out to be a new language
called Ada-named for Countess Ada Lovelace, "the first programmer"
(see Appendix B). Sponsored by the Pentagon, Ada was originally intended
to be a standard language for weapons systems, but it has also been used
successfully for commercial applications. Introduced in 1980, Ada has the
support not only of the defense establishment but also of such industry
heavyweights as IBM and Intel, and Ada is even available for some personal
computers. Although some experts have said Ada is too complex,
others say that it is easy to learn and that it will increase productivity.
Indeed, some experts believe that it is by far a superior commercial language
to such standbys as COBOL and FORTRAN.
Widespread use of Ada is considered unlikely by many experts.
Although there are many reasons for this (the military services, for
instance, have different levels of enthusiasm for it), probably its size-
which may hinder its use on personal computers-and complexity are the
greatest barriers. Although the Department of Defense is a market in itself,
Ada has not caught on to the extent that Pascal and C have, especially in
the business community.
A language invented by Dennis Ritchie at Bell Labs in 1972, C produces
code that approaches assembly language in efficiency while still offering
high-level language features. C was originally designed to write systems
software but is now considered a general-purpose language. C contains
some of the best features from other languages, including Pascal. C compilers
are simple and compact. A key attraction is that it is independent of
the architecture of any particular machine, a fact that contributes to the
portability of C programs. That is, a C program can be run on more than
one type of computer after it has been compiled for that machine.
Although C is simple and elegant, it is not simple to learn. It was developed
for gifted programmers, and the learning curve may be steep.
Straightforward tasks may be solved easily in C, but complex problems
require mastery of the language.
An interesting side note is that the availability of C on personal computers
has greatly enhanced the value of personal computers for budding software
entrepreneurs. A cottage software industry can use the same basic
tool-the language C-used by established software companies such as
Microsoft and Borland. Today C is has been replaced by its enhanced