Information Technology Reference
In-Depth Information
machine cycle. Like writing a report or a paper in English, writing a computer program in a
programming language requires the programmer to follow a set of rules. Each programming
language uses symbols that have special meaning. Each language also has its own set of rules,
called the
syntax
of the language. The language syntax dictates how the symbols should be
combined into statements capable of conveying meaningful instructions to the CPU. A rule
that “Variable names must start with a letter” is an example. A variable is a quantity that can
take on different values. Program variable names such as SALES, PAYRATE, and TOTAL
follow the rule because they start with a letter, whereas variables such as %INTEREST,
$TOTAL, and #POUNDS do not.
syntax
A set of rules associated with a pro-
gramming language.
The Evolution of Programming Languages
The desire to use the power of information processing efficiently in problem solving has
pushed the development of newer programming languages. The evolution of programming
languages is typically discussed in terms of generations of languages (see Table 4.9).
Table 4.9
Generation
Language
Approximate
Development Date
Sample Statement
or Action
The Evolution of Programming
Languages
First
Machine language
1940s
00010101
Second
Assembly language
1950s
MVC
Third
High-level language
1960s
READ SALES
Fourth
Query and database
languages
1970s
PRINT EMPLOYEE
NUMBER IF GROSS
PAY>1000
Beyond
Fourth
Natural and intelligent
languages
1980s
IF gross pay is greater
than 40, THEN pay the
employee overtime pay
Visual, Object-Oriented, and Artificial Intelligence Languages
Today, programmers often use visual and object-oriented languages. In the future, they will
likely be using artificial intelligence languages to a greater extent. In general, these languages
are easier for nonprogrammers to use compared with older generation languages.
Visual languages
use a graphical or visual interface for program development. Unlike
earlier languages that depended on writing detailed programming statements, visual lan-
guages allow programmers to “drag and drop” programming elements and icons onto the
computer screen. Many of these languages are used to develop Web applications.
Visual
Basic
was one of the first visual programming languages. Microsoft Visual Studio is a set of
object-oriented programming languages and tools to develop Windows and Web-based
applications. You can develop applications that can range from a simple Web-based program
for displaying your résumé to complex business applications that process customer orders,
control inventory, and send out bills—using languages such as Visual Basic .NET, Visual
C++ .NET, Visual C#, and Visual J#.
C++
is a powerful and flexible programming language
used mostly by computer systems professionals to develop applications.
Java
is an object-
oriented programming language developed by Sun Microsystems that can run on any OS
and on the Internet. Java can be used to develop complete applications or smaller applications,
called
Java applets
. Many of these languages are also examples of object-oriented languages,
which are discussed next.
The preceding programming languages separate data elements from the procedures or
actions that will be performed on them, but another type of programming language ties them
together into units called
objects
. An object consists of data and the actions that can be per-
formed on the data. For example, an object could be data about an employee and all the
operations (such as payroll calculations) that might be performed on the data. Programming
languages that are based on objects are called
object-oriented programming languages
.
