Programming language:
A
programming language is a set of rules that tells the computer what operations
to do. These languages are used by the programmers to create other kinds of
software.
Generations of Programming
Languages
The
five generation of programming languages start at the lowest level with
(l) machine language. They then range up
through
(2)
assembly language,
(3)
high level languages (procedural and object-oriented languages), and
(4) very high level languages
(problem-oriented languages). At the highest level are
(5) natural languages.
First Generation: Machine Language
Machine
language is the basic language of the computer, representing data as 1s and Os.
Each CPU model has its own machine language: Machine language programs vary
from computer to computer, i.e., they are machine-dependent. . These binary
digits, which correspond to the on and off electrical states of the computer,
are clearly not convenient for people to read and use.
Advantages:-
·
Very
efficient
·
Require
less storage space
Disadvantages:-
·
Machine
dependent
·
Programming
is difficult
Second Generation: Assembly Language
assembly
language is a low-level programming language that allows a computer user to
write a program using abbreviations or more easily remembered words instead of
numbers, A programmer can write instructions in assembly language more quickly
than in machine language, In these languages, each numeric instruction is
assigned a short name (called a mnemonic) that is easier to remember than a
number.
Advantages:-
- It is easier to modify than
machine language
- Easier to understand and use
Disadvantages:-
- The coding to assembly
language is time consuming
- They are also machine
dependent
An assembler, or
assembler program, is a program that translates the assembly-language program
into machine language.
Assembler
An
assembler is a computer program that translates assembly language statements
into machine language codes. The assembler takes each of the assembly language
statements from the source code and generates a corresponding bit stream using
O's and 1 's. The output of the assembler in the form of sequence of O's and
l's is called object code or machine code. This machine code is finally
executed to obtain the results.
Third Generation: High-Level or Procedural
Languages
A high
level or procedural language resembles some human language such as English. For
example, COBOL, which is used for business applications. A procedural language
allow users to write in a familiar notation, rather than numbers or
abbreviations, Also, unlike machine and assembly languages, most of procedural
languages are not machinedependent-i.e., they can be used on more than one
kind of computer. Few examples, are FORTRAN, COBOL, BASIC and Pascal.
For a
procedural language we need language translator to translate it into machine
language. Depending on the procedural language we may use either of the
following types of translators: -
Compiler
The
compiler is a computer program that translates the source code written in a
high-level language into the corresponding object code of the low-level
language. This translation process is called compilation. The entire high-level
program is converted into the executable machine code file. Compiled languages
include COBOL, FORTRAN, C,C++, etc.
Interpreter
The
interpreter is a translation program that converts each high-level program
statement into the corresponding machine code. This translation process is
carried out just before the program statement is executed. Instead of the
entire program, one statement at a time is translated and executed immediately.
The commonly used interpreted language is BASIC and PERL.
Compiler
(a)
Scans the entire program first and translates it into machine code.
(b)
Converts the entire program to machine code
(c)
Slow for debugging (removal of mistakes from a program).
(d)
Execution time is less.
Interpreter
(a)
Translates the program line by line.
(b)
Each time the program is executed, every line is checked for syntax error and
then converted to equivalent machine code.
(c)
Good for fast debugging.
Advantages:-
· These are easy to learn.
· Easier to maintain.
· They are not machine dependent.
· Programs are portable.
Fourth
Generation: Problem Oriented Languages
Third-generation
languages tell the computer how to do something. Fourth generation languages,
in contrast, tell the computer what to do. Very high-level or problem-oriented languages, also called
fourth-generation languages (4 GLs),
are much more user-oriented and allow users to develop programs with fewer
commands compared with procedural languages, although they require more
computing power. These languages are known as problem-oriented because they are designed to solve specific
problems, whereas procedural languages are more general-purpose languages.
Three
types of problem-oriented languages are report generators, query languages, and
application generators.
Report generators
A report generator, also known as
a report writer, is a program for end-users that produces a report. The report
may be a printout or a screen display.
Query languages
A query language is an
easy-to-use language for retrieving data from a database management system.
Application generators
An
application generator is a programmer's tool consisting of modules that have
been preprogrammed to accomplish various tasks
Fifth Generation: Natural Languages
Natural languages are of two types. The first are
ordinary human languages: English, Spanish etc. The second are programming
languages that use human language to provide people a more natural connection
with computers.
Natural
languages are part of the field of study known as artificial intelligence. Artificial
intelligence (AI) is a group of related technologies that attempt to develop
machines capable of emulating human-like qualities, such as learning,
reasoning, communicating, seeing and hearing.
Use of High Level Programming Languages for the Systematic Development
of Programs
Let us
now consider some of the third-generation, or high-level languages in use
today.
Examples: BASIC, COBAL,
BASIC
Advantage:
The primary advantage of BASIC is its ease of use.
Disadvantages: Its processing speed is slow.
COBOL:
COBOL
is the language of business and it was formally adopted in 1960, COBOL (for Common Business-Oriented
Language) is the most
frequently used business programming language for large computers. Its most
significant attribute is that it is extremely readable. For example, a COBOL
statement might be :
MULTIPLY
HOURLY-RATE BY HOURS-WORKED GIVING TOTAL-PAY
COBOL,
too, has both advantages and disadvantages.
Advantages:
(1) It is machine independent.
(2) Its
English-like statements are easy to understand, even for a nonprogrammer.
(3) It
can handle many files, records, and fields.
(4) It
easily handles input/output operations.
Disadvantages:
(1)
Because it is so readable, it is wordy. Thus, even simple programs are lengthy,
and programmer productivity is slowed.
(2) It
cannot handle mathematical processing as well as FORTRAN
FORTRAN:
FORTRAN
is the language of mathematics and the first high-level language. It was
developed in 1954 by IBM; FORTRAN (for FORmula TRANslator) was
the first high-level language. Originally designed to express mathematical
formulas, it is still the most widely used language for mathematical,
scientific, and engineering problems. It is also useful for complex business
applications, such as forecasting and modeling.
FORTRAN
has both advantages and disadvantages:
Advantages:
(1)
FORTRAN can handle complex mathematical and logical expressions
(2) Its
statements are relatively short and simple.
(3) FORTRAN
programs developed on one type of computer can often be easily modified to work
on other types.
Disadvantages:
(1)
FORTRAN does not handle input and output operations to storage devices as
efficiently as some other higher-level languages.
(2) It
has only a limited ability to express and process non-numeric data.
(3) It
is not as easy to read and understand as some other high-level languages.
Pascal:-
Pascal
is the simple language. Named after the 17th-century French mathematician
Blaise Pascal, Pascal is an alternative to BASIC as a language for
teaching purposes and is relatively easy to learn. A difference form BASIC is
that Pascal uses structured programming.
A
compiled language, Pascal offers these advantages and disadvantages:
Advantages:
(1)
Pascal is easy to learn.
(2) It
has extensive capabilities for graphics programming. (3) It is excellent for
scientific use.
Disadvantage:
Pascal has limited input/output programming capabilities, which limits its
business applications.
C++ is an Object Oriented Programming (OOP)
language. In C++-the plus signs stand for "more than C"-which
combines the traditional C programming language with object-oriented
capability. C++ was created by Bjame Stroustrup. Three important
concepts of OOP are:
Encapsulation,
Inheritance, Polymorphism
Advantages
(1) It
is portable.
(2)
Once the programmer has written a block of program code, it can be reused in
number of program.
GUI based Languages
The Graphical User Interface (GUI as the name suggests,
uses illustrations for text, which help users to interact with an application.
This feature makes it easier to understand things in a quicker and easier way.
Visual Basic: Visual Basic
is an example of visual programming. Visual BASIC is a Windows-based,
object-oriented programming language from Microsoft that lets users develop
Windows and office applications.
Visual C++ : This
language is a GUI extension of conventional C++ language. It is a part of
Microsoft Visual Studio software package. It is an Object Oriented Programming
language that has been designed for producing high level object oriented
applications, that can work with hardware devices, for example-Windows
applications and device drivers.
Techniques for designing program are:-
·
Top-down
Design (Stepwise Refinement)
· Modular Approach
· Structured Programming
Structured Programming
Structured programming takes a top-down
approach that breaks programs into modular forms. The main objectives of structured programming are
·
Efficiency
·
Readability
·
Clarity
of programs
·
Easy
modification
·
Reduced
testing problems.
The goto statement should be avoided so far as possible. The
three basic building blocks are given below
Sequence Control Structure : It consists of a
single statement or a sequence of statements with a single entry and single
exit
Loop or Iteration:- It consists of a condition (simple or compound ) and
sequence structure which is executed condition based
Binary decision structure:- It consists of a condition (simple or compound ) and two
branches out of which one is to be followed depending on the condition being
true or false
DESIGN AND IMPLEMENTATION OF CORRECT,
EFFICIENT AND MAINTAINABLE PROGRAMS
The
design and development of a correct, efficient, and maintainable program
depends on the approach followed by the programmer. A programmer should follow
standard methodologies throughout the life cycle of program development. The
entire program development process is divided into a number of phases, with
each phase serving a definite purpose. Also, the output of one phase acts as an
input for the next phase. Let us now understand these standard set of phases in
the program development process:
Analysis phase:
As the name suggests, the first phase of
program development involves analyzing the problem in order to ascertain the
objectives that the program is supposed to meet. All the identified
requirements are documented so as to avoid any doubts or uncertainties
pertaining to the functionality of the program.
Designing phase:
This
phase involves making the plan of action before actually starting the
development work. The plan is made on the basis of the program specifications
identified in the previous phase. Different programs require different
designing patterns depending on the program specifications.
Development phase:
This
phase involves writing the instructions or code for the program on the basis of
the design document created in the previous phase. The choice of the
programming language in which the program will be developed is made on the
basis of the type of program.
Implementation and Testing:
In this stage, the developed program is
implemented in its target environment and its key parameters are closely
observed in order to ensure that the program runs correctly. Apart from
ensuring the correct functioning of the program this phase primarily focuses on
identifying the hidden bugs in the program.
