Java Reference
In-Depth Information
1.3.3 High-Level Language
In the 1950s, a new generation of programming languages known as
high-level languages
emerged. They are platform independent, which means that you can write a program in a high-
level language and run it in different types of machines. High-level languages are English-like
and easy to learn and use. The instructions in a high-level programming language are called
statements.
Here, for example, is a high-level language statement that computes the area of a
circle with a radius of
5
:
high-level language
statement
area = 5 * 5 * 3.14159;
There are many high-level programming languages, and each was designed for a specific
purpose. Table 1.1 lists some popular ones.
T
ABLE
1.1
Popular High-Level Programming Languages
Language
Description
Ada
Named for Ada Lovelace, who worked on mechanical general-purpose computers. The Ada language was
developed for the Department of Defense and is used mainly in defense projects.
BASIC
Beginner's All-purpose Symbolic Instruction Code. It was designed to be learned and used easily by beginners.
C
Developed at Bell Laboratories. C combines the power of an assembly language with the ease of use and
portability of a high-level language.
C++
C++ is an object-oriented language, based on C.
C#
Pronounced “C Sharp.” It is a hybrid of Java and C++ and was developed by Microsoft.
COBOL
COmmon Business Oriented Language. Used for business applications.
FORTRAN
FORmula TRANslation. Popular for scientific and mathematical applications.
Java
Developed by Sun Microsystems, now part of Oracle. It is widely used for developing platform-independent
Internet applications.
Pascal
Named for Blaise Pascal, who pioneered calculating machines in the seventeenth century. It is a simple,
structured, general-purpose language primarily for teaching programming.
Python
A simple general-purpose scripting language good for writing short programs.
Visual Basic
Visual Basic was developed by Microsoft and it enables the programmers to rapidly develop graphical user
interfaces.
A program written in a high-level language is called a
source program
or
source code.
Because a computer cannot execute a source program, a source program must be translated
into machine code for execution. The translation can be done using another programming tool
called an
interpreter
or a
compiler.
source program
source code
interpreter
compiler
An interpreter reads one statement from the source code, translates it to the machine code
or virtual machine code, and then executes it right away, as shown in Figure 1.4a. Note
that a statement from the source code may be translated into several machine instructions.
■
A compiler translates the entire source code into a machine-code file, and the
machine-code file is then executed, as shown in Figure 1.4b.
■
1.10
✓
✓
What language does the CPU understand?
Check
1.11
Point
What is an assembly language?
1.12
What is an assembler?
1.13
What is a high-level programming language?
1.14
What is a source program?
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