Chapter-6 CONCEPT OF PROGRAMMING AND PROGRAMMING LANGUAGES
CHAPTER NO.6 CONCEPT OF PROGRAMMING AND
PROGRAMMING LANGUAGES
6.1 INTRODUCTION
In this chapter, we are going to learn about the
concept of program, programming,
programming process and different categories of
programming languages used for computer systems, A program is basically a set
of instructions to be executed by computer to perform
some task. The process of writing a program is
called programming. The person who writes the program is called programmer.
When a programmer writes a program, he or she goes through a particular
process. This process of developing a program is called programming process.
The programmer can use any language from hundreds of available programming
languages for program development.
6.2 CONCEPT OF PROGRAM AND PROGRAMMING
We lmow that a computer system basically consists of
two parts: hardware and software.Without software, computer-hardware cannot do
anything hence computer is nothing but a piece of metal without software. To
make the computer-hardware to do something, we must install and use software in
our computer system. Now the question arises what is software?
Software is a set of computer programs which are
designed and developed to perform desired tasks on computer. It is the software
which makes a computer capable of data processing,storing and retrieval.
Basically, softwares are categorised into two types: system software and application
software. System software are designed and developed to control the
functionality & to operate computer system hardware while the application
software are designed and developed to perform specific tasks using computer
system. System softwares are more complex as compared to application softwares.
The development (programming) of system softwares require more skills as
compared to application software development.
Software is usually not a single entity. It is a set (collection) of programs. A programmer must write instructions in a prescribed sequence of the programming language being used for development so that the computer system becomes capable of successfully performing the desired task. Thus, we can say that a Program is a set of Instructions that the computer executes.
The process of writing system program is known as System programming and the programmer for the same is called System Programmer whereas writing application program is known as application programming and the programmer for the same is called application programmer,
6.3 PROGRAMMING LANGUAGES
The programming languages are similar to natural
languages which are used in our daily life such as Punjabi, Hindi and English
etc. As we use natural languages for communication purposes, similarly computer
programming languages are used to communicate with the computer systems and to
make computers work as desired through softwares.System programs (Example:
Operating Systems) are designed to control & operate the input/output
devices, memory, processor etc. To write system program, such as operating
system, programmer needs to control the hardware components of computer system.
It is possible only if the programmer knows the internal architecture of
hardware components.Therefore, system programming is the task of skilled
programmers that have a detailed knowledge
of the hardware components of the computer system.
Machine, Assembly and C languages are widely used to develop system
programs.Application programs are developed to perform a particular task or to
solve a particular problem. For example: student management system, library
management system, payroll system,inventory control system, word processors,
spread sheets, graphics software etc are application
programs. Application programmer does not need to
possess in-depth hardware knowledge.The most popular application programming
languages are PYTHON, COBOL, FORTRAN,BASIC, PASCAL, C, C++, JAVA ete.
6.3.1 Types of Programming Languages
In this era, hundreds of programming languages are
available. These languages are categorised on the basis of their ability to
develop different kinds of software. Some of the programming languages are best
for writing system software while some others are best suitable for writing
application software or mobile applications:
For designing and developing system programs, low
level programming languages are used while for developing application-programs,
many high level programming languages have been designed. Let's know more about
different type of programming languages:
A. Low Level Languages : Machine language and
assembly languages are called low
level languages. These programming languages are
close to computer hardware and have more direct access to the features of the
hardware. These are used to develop drivers, high performance code, kernels for
operating systems etc. A detailed explanation of low-level languages is given
below:
a. Machine Language : Machine language is also known
as Binary Language. It is
considered as the first generation of computer
programming languages. Machine
language is the fundamental language for computer
systems because this language is
directly understood by the computer hardware. Unlike
high level programming
languages, there is no need for translation of machine language code to make it understandable by the computer. This language consists of only two binary digits - 0 and 1.
Every instruction in machine language consists of two parts: Opcode and operand, as shown in the diagram below:
Fig. 6.3 Instruction Format in Machine Language
Here, Opcode is the Operation Code and Operand is
the Operation Address, The first part - Operation code is the command which
tells the computer what operation is
going to be performed. The second part - Operation
Address is the memory address
which tells the computer where to find the data for
the operation to be performed.
Because the instruction codes are written using
binary digits 0 and 1 only, so it
becomes difficult to remember the machine
instruction codes in binary format. There
ate many advantages and disadvantages of using
machine language some of which
are explained below:
Advantages of Machine Language:Binary format
instructions are directly understood by computer without any
translation.Machine instructions are executed fast
because these are executed directly without any translation.
Disadvantages of Machine Language:
It is difficult to remember the machine instruction
codes as they are made up of
complex combinations of binary digits 0 and 1.
It is the most difficult process to find errors in
the machine instruction codes.
Highest level of knowledge of low-level internal
details of hardware is required for programming in machine language.
Programs developed in machine language are machine
dependent because machine
instructions are written according to the underlying
architecture of computer system.So, these instructions are machine specific
which cannot be executed on the computer systems having different architecture.
b. Assembly Language : This language is also known
as Symbolic Language because
symbolic names of instructions are used instead of
binary codes. This language is
considered as second generation of computer
programming languages. The major
benefit of assembly language as compared to machine
language is that it reduces
coding time and the amount of information the
programmer has to remember. The
symbolic names of instructions can be easily
remembered therefore it also becomes easy to find errors in the program and to
modify it as compared to machine language.Despite of these benefits,
programming in assembly language still requires in-depth technical knowledge of
hardware. So, programmer must be aware with the machine architecture for
programming in assembly language. Due to this hurdle, programs written in
assembly language are still machine-dependent. These programs cannot be
executed on other machines having different architectures.
Symbolic names used for operation codes in Assembly
Language are called Mnemonic
Codes. For example: the codes for addition,
subtraction, multiplication, and division operation are ADD, SUB, MUL and DIV
respectively in Assembly language. These codes are the examples of Mnemonic
codes.
Now the question arises how do computers execute the
assembly language code
because computers can execute instructions only in
binary format. In order to execute
an assembly language code on a computer, it must be
translated into equivalent
machine understandable code. For this translation, a
translator program, named
Assembler, is used. Assembler is a language
translator program which translates the assembly language code into equivalent
machine code. In the following sections, we will study in detail about the
assemblers.
Advantages of Assembly Language:
It is easy to learn and remember the codes of
assembly language because it uses
English like codes instead of binary digits as
compared to machine language.
Finding and correcting errors in the assembly
language program is easy when compared to machine (binary) language.
Assembly language programs have the equivalent
efficiency of the machine language programs.
Disadvantages of Assembly Language:
Knowledge of low level internal details of hardware
is required for programming in
assembly language. Therefore hardware technical
skills are required for the programmer to do programming in assembly language.
Programs developed in Assemblylanguage are machine
dependent because assembly
instructions are written according to the underlying
architecture of computer system.So these instructions are machine specific
which cannot be executed on the computer systems having different architecture.
B. High Level Languages :
The primary objective of developing high level languages is that these
languages facilitate a large number of people to build programs or software
without
the need to know the intemal low level details of
computer system hardware. These languages are designed to be
machine-independent.
High level languages are English like languages.
These languages use simple & special characters and numbers for
programming. Therefore, these languages make it easy for common people to learn
and write computer programs. An instruction written in high level language is
usually called a Statement. Each high level language has its own rules for
writing program instructions. These rules are called Syntax of the language.
Some of the commonly used High Level Languages are: PYTHON, BASIC, COBOL,
FORTRAN, PASCAL, C, C++, JAVA, C SHARP etc.
Similar to Assembly Language, high level languages
cannot be directly understood by
computer systems. Language translators are required
for translating them into machine
understandable format. There are two approaches for
translating high level languages into
machine code: first is via Compiler and other is via
Interpreter. Each high level language has its own translator program. We cannot
translate a program written in one specific high level language with the
compiler of some other specific language. For example, we cannot compile C
program using COBOL compiler or vice-versa.
Some of the common categories of high level
languages are discussed below:
Procedural or Procedure Oriented Languages :
Procedural languages are considered
as the Third Generation of Programming Languages
(3GLs). In procedural
languages, a program can be written by dividing it
into small procedures or subroutines.
Each procedure contains a series of instructions for
performing a specific task.Procedures can be re-used in the program at
different places as required.These languages are designed to express the logic
of a problem to be solved. The order of program instructions is very important
in these languages.Some popular Procedural languages are FORTRAN, COBOL,
Pascal, C language etc.
Problem-Oriented or Non-Procedural Languages :
Problem oriented languages
are also known as Non-Procedural languages. These
languages are considered as the Fourth Generation of Programming Languages
(4GL). These languages have
simple, English-like syntax rules and they are
commonly used to access databases. It
allows the users to specify what the output should
be instead of specifying each step one after another to perform a task. It
means there is no need to describe all the details of how the data should be
manipulated to produce the result. This is one step ahead
from third generation programming languages. These
languages provide the user-friendly program development tools to write
instructions.Using these languages, user writes the program using application
generator that allows data to be entered into the database. The program prompts
the user to enter the needed data and then it checks the data for its validity.
Examples of problem oriented languages are: SQL (Structure Query Languages),
Visual Basic, C# etc. The objectives of these languages are to increase the
speed of developing programs and reduce errors while writing programs.
Object-Oriented Programming Languages :
The Object-Oriented programming
concept was introduced in the late 1960s, but now it
has become the most popular
approach to develop software.In these programming
languages, a problem can be
solved by dividing it into a number of objects.
Object-Oriented languages support the concept of object, class, encapsulation,
data hiding, inheritance and polymorphism etc.Now-a-days, most popular and
commonly used Object-Oriented programming (OOPs) languages are C++ and Java.
Logic-Oriented languages : These languages use logic
programming paradigms as
the design approach for solving various
computational problems. Any program
written in a logic programming language is a set of
sentences in logical form. These
sentences express facts and rules about some problem
domain, Major logic
programming language families include Prolog, Answer
Set Programming (ASP) and
Datalog. In all of these languages, rules are
written in the form of clauses. Such
languages are very beneficial in the field of
Artificial Intelligence and Robotics.
Advantages of High Leve} Languages : Some of the
common advantages of high level
languages are given below:
High Level languages are easy to learn and
understand as compared to low level
languages. It is because the programs written in
these languages are similar to
English-Like statements.
The errors in a high level language program can be
easily detected and removed. All the syntax errors are detected and removed
during the compilation process of the program.
These languages provide a large number of built-in
functions that can be used to
perform specific task during programming which
results in huge time saving i.e.
much faster development.
Programs written in high level language are machine
independent. A program written
for one type of computer architecture can be
executed on another type of computer
architecture with little or no changes.
Disadvantages of High Level Languages : Some of the
common disadvantages of high
level languages are given below:
A program written in high level languages has lower
efficiency & speed as compared
to equivalent programs written in low level
languages.
Programs written in high level languages require
more time and memory space for
execution.
High level languages are less flexible than low
level languages because normally
these languages do not have direct interaction with
computer's hardware such as CPU, memory and registers.
6.4 LANGUAGE TRANSLATORS
Language translators are also called Language
Processors. These are the system programs which are helpful to develop
programs. Language translators are designed primarily to perform
two main functions as described below:
These are designed to translate source programs into
machine's object code. Source programs may be written in Assembly Language or
High Level languages while
object code is a code that a computer CPU can
understand without any translation.
These translator programs are also designed to
detect any syntax errors in the source program. Successful translation of
source program into object program takes place only if the source program does
not have any syntax errors in it.
Each language has its own translator program which
can translate the program written only in that specific language. Assembler is
a translator program which can translate the source program written in assembly
language only. Similarly each high level language has its own
translator program, known as Compiler and
Interpreter. Some High level languages use Compiler (for example: C/C++
Language) while some other uses Interpreter (for example: BASIC language). But
there exists also some languages which have both compiler and interpreter for
different levels of translation, for example: JAVA is a language which has both
compiler and
interpreter. All these types of translator programs
are discussed below:
6.4.1 Assembler
It is a language translator which converts assembly
language program into machine-
understandable format. The program written in assembly language is called Source Program.This source program cannot be directly understood by the computer system. That is why it must be translated into machine understandable format for the execution. It is the assembler which translates this assembly language source program into machine understandable program.The soutce program after translation (in machine understandable form) is called Object Program (Code). This object program is provided to processer for execution.
As shown above the input to assembler is an Assembly Language
Program and the output of assembler is a program is in the machine
understandable from.
6.4.2 Interpreter and Compiler
There are two types of language translators for High
level languages i.e. 1. Interpreters
2.Compilers
These translators are used for translating source
programs written in High Level
languages into machine understandable form,In the
first approach, i.e, Interpreter, one statement of high level language program
is taken at a time and it is translated into machine instruction which is
executed immediately by the
processor. It means no object program is saved in
this approach of translation. Whenever we want to execute the program we have
to translate the source program every time.
Interpreters do not require large memory space to
translate and execute programs. The main disadvantage of interpreters is that
they require same amount of time whenever we execute programs on a computer
system because every statement of source program must be translated every time.
In the other approach, i.c. Compiler, all statements
of the high level language program are taken at a time and they are translated
into machine understandable form which is stored as Object Program in Memory.
This object program is provided to computer system whenever program is
executed. Compilers take more time to translate source program as compared to
interpreter. But compiled object program runs much
faster than the interpreted program.
Each High Level language has its own compiler. We
cannot compile the source code of one language with the compiler of another
language. For example FORTRAN compiler cannot compile the source code written
in COBOL language and vice-versa.
The difference between an interpreter and a compiler
may be understood with the help of following analogy. Suppose we want to
translate a speech from Tamil to Hindi. We can use two approaches to do this
translation. In first approach, translator listens to a sentence in Tamil and
immediately translates it into Hindi. In the second
approach, the translator listens to the whole passage in Tamil and then gives
the equivalent Hindi passage. An interpreter is similar to first
approach of translation where sentence-by-sentence
translation is carried out whereas compiler is similar to second approach where
whole passage is translated in a single step.
6.5 PROGRAMMING PROCESS
We know that a computer needs a program to tell it
what to do. Instructions in the program guide the computer how to solve the
given problem. But developing a program is not a simple and easy task. A
programmer has to go through a specific process for developing a program
successfully. The steps involve in the programming
process are listed below and are required to be followed in the same sequence:
1. Defining the problem to be solved
2. Pian the solution of the problem
3. Coding the solution in the high level language
4. Compile the program
5. Test and Debug the program
6. Decumenting the program
These steps can be explained in detail
as follows:
6.5.1 Defining the problem
It is the first step in the programming process.
Before a programmer begins his task, he must need to know the extensive details
of the problem to be solved through programming. The details of the problem should
be provided to the programmer so that he gets a clear understanding of it.
Analysis of the problem shows what the required inputs and outputs will be for
the solution of problem. After having a clear understanding of the problem,
programmer starts thinking about how to solve the given problem.
6.5.2 Planning the Solution
The next step after defining the problem is to
prepare a detailed list of steps required to be catried out for solving the
problem, We will take an example which shows why planning is required for
solving the problem. A teacher asks the student to solve a specific
mathematical problem and the student is not familiar with the steps involved in
solving the problem. Thus, he
would not be able to solve it. The same principle
applies to writing computer programs also. A programmer cannot write the
instructions for any program unless he understands how to solve the problem
manually.
If a programmer knows the steps for solving the
problem but while programming, if he applies the steps in the wrong sequence or
he forgets to apply any of these steps, he will get a wrong output or even no
output at all. Hence to write an effective program, a programmer has
to write all instructions in the correct sequence.
Therefore, to ensure that the instructions of the program are appropriate and
are in the correct sequence, the programmer must plan the
program before start writing it. For planning and
defining the steps for the programs,programmers normally use Algorithms and
Flow-Charts. Both of these approaches are explained below in detail:
6.3.2.1 Algorithms
The development of an algorithm is basic requirement
to computer programming. It is a step-by-step description of how to solve a
given problem. An algorithm consists of finite steps and a guaranteed result.
When these steps are carried out as specified in the algorithm, it produces the
required output. The construction of the algorithm requires creative
thinking.Before developing a program, a programmer first set out the algorithm
so that he can visualize the possible alternatives to solve the given problem.
In order to qualify for the sequence of steps, to be called an algorithm, it
should have the following features:
1, Each step should be accurate.
2. Each step should be unambiguous, i.e. it should
not have dual meaning.
3. The inputs and outputs should be carefully
specified.
4. Steps should not be repeated infinitely.
5. After executing the steps, the required output
must be produced.
To gain a clear understanding of algorithms, let us
consider some simple examples of defining algorithms.
Problem Statement 1 : Calculate and print
multiplication of two numbers:
Algorithm-I:
Step1: Start
Step2: Read two numbers A and B.
Step3: Multiply A and B and store result in C.
Step4: Print C.
Step5: Stop.
Problem Statement 2: Write an algorithm to find
whether a given number is Odd
or Even.
Algorithm-IT;
Step1: Start
Step2: Read a Number A
Step3: Divide the number A by 2 and get remainder
value
Step4: If remainder of the division is zero then
Print "Number is Even"Else
Print “Number is Odd"
Step5: Stop
Problem Statement 3: Write an algorithm to print
“India is Great" 10 times:
Algorithm-III:
Step1: Start
Step2: Count = 1
Step3: While (Count<=10)
Step4: Print “India is great"
StepS: Count=Count + 1
[End of While loop]
Step6: Stop
6.5.2.2 Flow Charts
Flow charts are the common ways to represent
algorithms. These are also frequently used by the programmers for planning of
the program. Programmers often find them very helpful for developing effective
and correct programs.
A flowchart is a pictorial representation of the
algorithm. Programmers often draw flow charts to visually organize the sequence
of steps defined in the algorithm. It uses different types
of symbols/shapes to represent different types of
instructions. The process of drawing a flowchart for an algorithm is known as
flowcharting.Normally, an algorithm is first represented as flowchart, and the
flow chart is then expressed in a programming language to develop a computer
program. The main advantage of this two-step approach in program development is
that a programmer can more easily detect logical
errors in the program logic because a flow chart
shows the flow of operations in the pictorial form. Once the flow chart is
ready, the programmer can concentrate only on coding of operations. This
normally ensures an error-free program.
Experienced programmers, sometimes, write programs
without drawing flowcharts.
However, beginners should first draw a flowchart to
effectively do the programming. Moreover,it is a good practice to have a flow
chart along with the computer program. It proves to be very
useful during testing of the program as well as
during modifications in the program.
Before preparing flowcharts, we have to learn about
the different symbols used in the flowcharts. Some of the basic symbols used in
the flowcharts are:
Now let us consider some examples of flowcharts sc
that we get familiar with the concept of flowcharts:
a. Draw a flowchart to Calculate and print
multiplication of two numbers
(Flowchart for Algorithm-I):
Now, we have a clear understanding of how to plan
the steps to solve the given problem.Once, inputs, outputs, algorithms and
flowcharts have been clearly defined, the next step is to translate these steps
into a program using High level programming languages.
6.5.3 Coding the Solution:
The sequence of operations defined in flow-chart can
be converted into instruction using some High-Level programming language, such
as C, C++, and PASCAL etc. Coding is the process of writing the instructions
using programming language to make a program. This
program file is known as source program or source
code. This code is stored in a disk file. This program contains the logic or
steps for solving the problem. For example, let us consider the following
source code using C language for the Algorithm-I:
6.5.4 Compile the program
After writing program code in High level language,
we have to translate it into such a form that computer can understand &
execute it because computer can understand instructions only in binary format.A
compiler is a small program that translates the source program into a
machine understandable form (i.c. object code). This
conversion of source code into object code is known as Compilation. During
compilation, compiler also scans the source program for syntax errors. If there
are syntax errors in the program, compiler generates error messages.
These errors must be corrected to generate the
object code. Then the object code will be stored in a disk file. Whenever we
want to execute the program, this object code is supplied to computer for
execution.
6.5.5 Testing and Debugging the Program
Testing and debugging are important steps in the
software development. Testing is a
process which makes it sure that program (software)
performs the intended task. Testing is a time-consuming task. As long as human
beings make programs, the programs will have errors.These program exrors are
called Bugs. The process of detecting and correcting such bugs is
called Debugging. Generally, two types of errors are
found in the programs:
Syntax Errors : These errors occur when we do not
follow the rules or syntax of
programming language being used. These types of
exrors are automatically detected
by compilers during compilation process. A program
cannot be successfully compiled
until all of the syntax errors in the program are
removed. Some examples of syntax errors in C language are: missing semicolon,
variable not declared, un-terminated string, compound statement missing etc.
Logical Errors : These errors occur when there are
errors in the logic of the program.If our program has logic errors, though it
will compile successfully but it may produce wrong result/output. Such types of
errors cannot be detected by the compilers.
These errors are either traced out manually by the
programmer or some debugging tools may be used to detect such errors.
Programmer can detect any faulty logic by examining the output.
6.5.6 Documenting the Program
The final stage in the development process of a
program is documentation. The term
documentation means specifying the important
information regarding the approach and logic applied in the program by the
programmer. The documentation enables other programmers to understand the logic
and purpose of the program. It is also helpful in the maintenance of the
program.
Pointseho
1. A Program is a set of instructions while a
Software is a set of programs.
2. A Programmer is the person who writes the program
code.
3. The Process of writing a program is called
Programming
4. Machine language is directly understood by
computer and consists of binary digits 0 and 1.
5. Assembly Language use mnemonic codes to write
instructions in the program.
6. High Level languages use alphanumeric codes to
write instructions in the program.
7. Assembler is a language translator which
translates Assembly language source program into machine understandable format
which is called Object Program Code.
8. Compiler is a language translator which
translates High Level language source program into machine understandable
format which is called Object code.
9. Algorithm is a set of finite steps to solve some
specific problem.
10. Flowchart is the pictorial representation of the
algorithm.
11. Writing the instructions to make a program using
some computer language is called coding.
12. Finding and correcting errors in the program is
called Debugging.
Part-A
1. Multiple Choice Questions
1. Set of instructions is called .
a Group
b. Software
c. Program
d. None of these
2 Which language is directly understood by
computer without any translation?
a. Procedure Oriented Language
b. Machine Language
c. Assembly Language
d. High Level Language
3. Mnemonic codes & symbolic addresses
are used in which programming language?
a. Object Oriented Language
b. Non-Procedural Language
c. Assembly Language
d. Machine Language
4. Which translator does not save object
code after translation of source program written in high level language?
a. Translator
b. Compiler
c. Assembler
d. = Interpreter
5. Process of finding and correcting errors
in a program is called
a. Compilation
b. Coding
c. Debugging
d. Documentation
2. Fill in the Blanks:
1. A person who writes the program is called
2 Lew level internal details of hardware are
required for programming in
3 is the pictorial representation of algorithm
4 Process of translating source program written in
high level language into object
code is called
5 Those errors which are not detected by the
compilers are called errors.
3. Write the Full form of following:
1. Opcode
2 Operand
3 4GL
4. SQL
5. OOP
Part-B
4. Short Answer Type Questions. (Write
the answers in 4-5 lines)
1. What is Programming?
2 What are Procedure Oriented Programming Languages?
3. Write the names of different symbols used in
flowcharts.
4. Write the steps used in Programming Process.
5. What are Syntax Errors?
Part-C
5. Long Answer Type Questions. (Write
the answers in 10-15 lines)
1. What are low level programming languages? Explain
their advantages and
disadvantages.
2 What are Language Translators? Explain any one
translator in detail.
3 What is algorithm? Explain the different features
that an algorithm should have.
4 Explain different types of errors found in the
computer programs.
