Introduction to Programming Concepts By Aamir Saleem Ansari

Author : Aamir Saleem Ansari
Web : www.techora.net

What is a program
Precise set of activities in a sequence to do something or to
solve some specific problem.
Computer Program
A computer program (also software, or just a program) is a
sequence of instructions written to perform a specified task with a
computer.
Set of ordered instructions that enable a computer to carry out a
specific task

 Is a way to communicate with each other
 Use to exchange (ideas, thoughts, needs,
emotions, feelings ) with each other
Programming Languages
 A computer language is a set of predefined words that are
combined into a program according to predefined rules (syntax)
Syntax
 Predefined set of rules to write the instructions in a
programming language is known as syntax.
 It’s a grammar of programming languages.

To write a program for a computer, we must use a
computer language. A computer language is a set of
predefined words that are combined into a program
according to predefined rules (syntax). Over the years,
computer languages have evolved from machine
language to high-level languages.
Evolution of programming languages

Machine languages
In the earliest days of computers, the only programming
languages available were machine languages. Each computer
had its own machine language, which was made of streams
of 0s and 1s.
i
The only language understood by a computer is machine
language.

Introduction to Programming Concepts By Aamir Saleem Ansari

Assembly languages
The next evolution in programming came with the idea of
replacing binary code for instruction and addresses with
symbols or mnemonics. Because they used symbols, these
languages were first known as symbolic languages. The set
of these mnemonic languages were later referred to as
assembly languages. The assembly language for our
hypothetical computer to replace the machine language in
Table 9.2 is shown in Program 9.1.

High-level languages
Although assembly languages greatly improved programming
efficiency, they still required programmers to concentrate on the
hardware they were using. Working with symbolic languages was also
very tedious, because each machine instruction had to be individually
coded. The desire to improve programmer efficiency and to change the
focus from the computer to the problem being solved led to the
development of high-level languages.
Over the years, various languages, most notably BASIC,
COBOL, Pascal, Ada, C, C++ and Java, were developed. Program 9.1
shows the code for adding two integers as it would appear in the C++
language.

#include<stdio.h>
#include<conio.h>
void main()
{
int n1,n2,n3;
printf(“Enter the first no”);
scanf(“%d”,&n1);
printf(“Enter the second no”);
scanf(“%d”,&n1);
n3 = n1 + n2;
printf(“ sum = %d “,n3);
getch();
}
Keyword:-
• Predefined words
which has special
meaning and purpose
in a programming
language
• C language has only
32 keywords

Keywords
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

Programs today are normally written in one of the high-
level languages. To run the program on a computer, the
program needs to be translated into the machine
language of the computer on which it will run. The
program in a high-level language is called the source
program. The translated program in machine language is
called the object program. Two methods are used for
translation: compilation and interpretation.
TRANSLATION

Compilation
A compiler normally translates the whole source program into the
object program.
Interpretation
Some computer languages use an interpreter to translate the source
program into the object program. Interpretation refers to the process of
translating each line of the source program into the corresponding line
of the object program and executing the line.

PROGRAMMING PARADIGMS
Today, computer languages are categorized according to
the approach they use to solve a problem. A paradigm,
therefore, is a way in which a computer language looks
at the problem to be solved. We divide computer
languages into four paradigms: procedural, object-
oriented, functional and declarative. Next diagram
summarizes these.

IDE (Integrated Development Environment)
IDE is a software that facilitate the programmer to
• Write the source code
• Debug the source code
• Compile the source code
• Execute the program
In a same environment.

 Write source code
 Vi and emacs for linux
 Eclipse, dev-c++, MS visual studio for
window

 In a C language, a preprocessor program
executes automatically before the compiler’s
translation phase begins.
 The C preprocessor obeys special commands
called preprocessor directives, which indicate
that certain manipulations are to be
performed on the program before
compilation.
 These manipulations usually consist of
including other files in the file to be compiled
and performing various text replacements.

 Check the syntax of whole program
 If there is an error compiler will display
the error in error window
 If there is no error then compiler
translate the source code into object
code
Compiler
First.c First.obj

 The next phase is called linking.
 C programs typically contain references
to functions defined elsewhere, such as
in the standard libraries or in the private
libraries of groups of programmers
working on a particular project.
 The object code produced by the C
compiler typically contains “holes” due to
these missing parts. A linker links the
object code with the code for the missing
functions to produce an executable
image (with no missing pieces).
Linker
First.obj First.exe

 Before a program can be executed, the
program must first be placed in memory. This
is done by the loader, which takes the
executable image from disk and transfers it
to memory.

 Finally, the computer, under the control
of its CPU, executes the program one
instruction at a time.

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Introduction to Programming Concepts By Aamir Saleem Ansari

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