http://cprogramming.language-tutorial.com/2012/01/program-to-find-given-number-is-perfect.html
http://free-c-programs.blogspot.in/
http://www.cquestions.com/2011/12/c-program-examples-with-output.html
http://cprogramming.language-tutorial.com/2012/01/program-to-find-given-number-is-perfect.html
History of C Programming Language
1. C is a programming language
which born at “AT & T’s Bell
Laboratories” of USA in 1972.
3. This language was created
for a specific purpose : to design the UNIX operating
system (which is used on many computers).
4. From the beginning, C was
intended to be useful to allow busy programmers to get things
done because C is such a powerful, dominant and supple
language, its use quickly spread beyond Bell Labs. in the
late 70’s
5. Many of its principles and
ideas were taken from the earlier language B.
6. Ken Thompson was the developer of B Language.
7. BCPL and CPL are the earlier ancestors of B Language
8. CPL is common Programming
Language.In 1967, BCPL ( Basic CPL ) was created as a scaled down version of
CPL
9. As many of the features
were derived from “B” Language thats why it was named as “C”.
10. After 7-8 years C++ came into
existence .
Summary of C Programming Language
History
Summary of C Programming History
|
||
1
|
B Language Developed By
|
Ken Thompson
|
2
|
Operating System Developed in C
|
UNIX
|
3
|
Developed at
|
AT & T Bell Laboratory
|
4
|
Creator of Traditional C
|
Dennis Ritchie
|
5
|
Year
|
1972
|
Father of C
Programming : Dennis Ritchie
Dennis Ritchie : General
Born On
|
September 9, 1941
|
Born in
|
Bronxville,New York,
|
Full Name
|
Dennis MacAlistair Ritchie
|
Nickname
|
DMR
|
Nationality
|
American
|
Graduate From
|
Harvard University
|
Graduate In
|
Physics and Applied Mathematics
|
Webpage
|
|
Dead On
|
October 12, 2011
|
Dennis Ritchie : Known for
No
|
What ?
|
1
|
Creator of C Programming
|
2
|
Creator of UNIX operating System
|
3
|
Co-author of “The C Programming Language”
|
Awards :
1982
|
Ritchie and Ken Thompson jointly received the Turing Award for
their development of generic operating systems theory
|
1999
|
Thompson and Ritchie jointly received the 1998 National Medal of
Technology from President Bill Clinton for co-inventing the
UNIX operating system and the C programming language
|
Chapter 2 : C Programming Basics
Features of C Programming Language :
C Programming is widely used in Computer Technology, We can say
that C Programming is inspiration for development of other languages. We can
use C Programming for different purposes. Below are some of the Features of C
Programming language -
1 . Low Level Features :
1. C Programming provides low level features that are generally provided
by the Lower level languages. C is Closely Related to Lower level Language such
as “Assembly Language“.
2 .Portability :
1. C Programs are portable i.e
they can be run on any Compiler with Little or no Modification
2. Compiler and Preprocessor
make it Possible for C Program to run it on Different PC
3 .Powerfull
1. Provides Wide verity of ‘Data Types‘
2. Provides Wide verity of
‘Functions’
3. Provides useful Control &
Loop Control Statements
4 . Bit Manipulation
1. C Programs can be manipulated
using bits. We can perform different operations at bit level. We can manage
memry representation at bit level. [Eg. We can use Structure to manage Memory at Bit Level]
2. It provides wide verity of
bit manipulation Operators. We have bitwise operators to manage Data at bit
level.
5 . High Level Features :
1. It is more User friendly as
compare to Previous languages. Previous languages such as BCPL,Pascal and other
programming languages never provide such great features to manage data.
2. Previous languages have there pros and
cons but C
Programming collected all useful features of previous languages thus C becomemore effective language.
6 . Modular Programming
1. Modular programming is a software design technique that increases the extent to which
software is composed of separate parts, called modules
2. C Program Consist of
Different Modules that are integrated together to form complete program
7 . Efficient Use of Pointers
1. Pointers has direct access to
memory.
2. C Supports efficient use of
pointer .
8 . More Efficient
Application Of C Programming
C Programming is best known
programming language. C Programming is near to machine as well as human so it
is called as Middle level Programming
Language. C
Programming can be used to do verity of tasks such as networking related,OS
related.
Application of C Programming are listed below -
1. C language is used for
creating computer applications
2. Used in writing Embedded
softwares
3. Firmware for various
electronics, industrial and communications products which use
micro-controllers.
4. It is also used in developing verification
software, test code, simulators etc. for various applications and
hardware products.
5. For Creating Compiles of different Languages which can take input from other language
and convert it into lower level machine dependent language.
6. C is used to implement
different Operating System Operations.
7. UNIX kernel is completely developed in C Language.
List of Applications of C
Programming
List of Application
|
||
Operating Systems
|
Network Drivers
|
Print Spoolers
|
Assemblers
|
Text Editors
|
|
Modern Programs
|
Data Bases
|
Language Interpreters
|
Simulators
|
Utilities
|
Embedded System
|
Definition of Compiler :
1. A computer program which
reads source code and outputs assembly code or executable
code is called
compiler.
2. A program that translates
software written in source code into instructions that a computer can
understand Software used to translate the text that a programmer writes into a format
the CPU can use.
3. A piece of software that
takes third-generation language codeand
translates it into a specific assembly code. Compilers can be quite complicated
pieces of software.
Compiler Overview :
Consider process of Executing Simple C Language Code –
We have opened C Code editor and wrote simple C Program , Whenever
we try to compile code and try to execute code our code is given to the
compiler.
intmain()
{
printf("Hello");
return(0);
}
Now our main intention is to
convert program into lower level language which can be read by Machine.
Compiler have different phases , and program undergoes through these 6 phases.
After Passing through all the compilation Phases our code is converted into the
machine level language code which can be read by machine.
Different Phases of Compiler
4. Intermediate Code Generation
5. Code Optimizer
6. Code Generation
What is Interpreter ?
1. Interpreter Takes Single instruction as input .
2. No Intermediate Object Code is Generated
3. Conditional Control
Statements are Executes slower
4. Memory Requirement is Less
5. Every time higher level program
is converted into lower level program
6. Errors are displayed for every instruction interpreted (if any)
7. The interpreter can immediately execute high-level programs, thus
interpreters are sometimes used during the development of a program, when a
programmer wants to add small sections at a time and test them quickly.
8. In addition, interpreters are often used in education because they allow students to program interactively.
Examples of Programming Languages
Using Interpreter :
Lisp
(defun convert ()
(format t "Enter Fahrenheit ")
(LET (fahr)
(SETQ fahr(read fahr))
(APPEND '(celsisus is)(*(-fahr32)(/59)))
)
)
BASIC
CLS
INPUT "Enter your name: ", Name$
IF Name$="Mike" THEN
PRINT "Go Away!"
ELSE
PRINT "Hello, "; Name$;". How are you today?"
END IF
Difference between Compiler and
Interpreter
No
|
Compiler
|
Interpreter
|
1
|
Compiler Takes Entireprogram as input
|
Interpreter Takes Singleinstruction as input .
|
2
|
Intermediate Object Code isGenerated
|
No Intermediate Object Code is Generated
|
3
|
Conditional Control Statements are Executesfaster
|
Conditional Control Statements are Executes slower
|
4
|
Memory Requirement :More (Since Object Code is Generated)
|
Memory Requirement isLess
|
5
|
Program need not becompiled every time
|
Every time higher level program is converted into lower level
program
|
6
|
Errors are displayed afterentire
program is
checked
|
Errors are displayed foreveryinstructioninterpreted
(if any)
|
7
|
Example : C Compiler
|
Example : BASIC
|
Explanation : Compiler Vs
Interpreter
Just understand the concept of the compiler and interpreter -
1. We give complete program as
input to the compiler. Our program is in the human readable format.
2. Human readable format
undergoes many passes and phases of
compiler and finally it is converted into the machine
readable format.
3. However interpreter takes
single line of code as input at a time and execute that line. It will terminate
the execution of the code as soon as it finds the error.
4. Memory requirement is less in Case of interpreter because no object code is
created in case of interpreter.
Following video will say much more about compiler -
Step By Step Execution Of C Program
Step 1 : Edit
1. This is First Step i.e Creating and Editing Program.
2. First Write C Program using
Text Editor , such as [ Borland C/C++ 3.0 , Notpad++,Notpad ]
3. Save Program by using [.C] Extension.
4. File Saved with [.C]
extension is called “Source
Program“.
Step 2 : Compiling
1. Compiling C Program : C
Source code with [.C] Extension is given as input to compiler and compiler
convert it into Equivalent Machine Instruction.
2. In Borland C/C++ 3.0 program
can be compiled using key [Alt + F9 ].
3. Compiler Checks for errors . If source code is error-free then Code is converted into Object
File [.Obj ].
Step 3 : Checking Errors
1. During Compilation Compiler will check for error, If
compiler finds any error then it will report it.
2. User have to re-edit the program.
3. After re-editing program , Compiler again check for any error.
4. If program is error-free then
program is linked with appropriate libraries.
Step 4 : Linking Libraries
1. Program is linked with included header files.
2. Program is linked with other
libraries.
3. This process is executed by Linker.
Step 5 : Error Checking
1. If run time
error occurs then “Run-time”
errors are reported to user.
2. Again programmer have to review code and check for the solution.
What is Low level Language in
Computer Science ?
·
Machine understandable Language.
·
Assembly is Common High Level Language
·
Internal Machine Code dependent
·
Fast to Run But slow to write
& Understand
What is machine Level Language ?
1. Machine code is the only
language a microprocessor can process directly without a previous transformation.
2. Currently, Programmers never
write programs directly in machine code, because it requires
attention to numerous details which a high-level language would handle
automatically.
3. Low Level Language Requires
memorizing or looking up numerical codes for every instruction that is used.
4. For this reason, second
generation programming languages provideone
abstraction level on top of the machine code.
Example: A function in 32-bit x86
machine code to calculate the nth Fibonacci number :
8B542408 83FA0077 06B80000 0000C383
FA027706 B8010000 00C353BB 01000000
B9010000 008D0419 83FA0376 078BD98B
C84AEBF1 5BC3
Higher Level Languages and Middle Level languages are different than Low Level Language in many aspects.
Summary of Lower Level Languages :
Low level languages are Machine Understandable, difficult to
write, requires more efforts to code and debug.
Middle Level Language ?
C Programming bridges gap
between traditional Machine Understandable Machine Level language and more conventional High level languages. User can Use C Language to do system programming for
writing operating system as well as application programming.
Middle Level Programming
languages are closely related to Machine as well as Human Being.
Why C is Middle Level Language ?
1. C Programming Supports Inline
Assembly Language Programs .
2. Using inline assembly
language feature in C we can directly access system registers.
3. C Programming is used to
access memory directly using pointer.
4. C Programming also Supports
high Level Language Features.
5. It is more User friendly as
compare to Previous languages so C programming is Middle Level Language.
C Language is Middle Level Language
Tips : Middle Level Language
1. Language is more Close to
Machine
2. Language is far from Human
i,e human need to take more efforts to code
3. We have to Write More Code to
meet user requirement and It is Easy to create Machine Level Code using C
Programming.
What
is high Level Language and its Execution Model ?
High level Language :
1. First high-level programming
languages were designed in the 1950s.
2. High level Language is Human understandable Language.
3. English is Common example of High Level Language.
4. High level Language is Internal Machine Code Independent.
5. High level Language is Program Oriented Language.
6. High level Language is Developed for providing GUI Interface.
Explanation :
As you can see the above diagram, it clearly shows that HLL are
more close to human and can be easily programmed as compare to lower level
language.In HLL Language and Machine gap is more.
C Programming can be considered as High Level / Low Level -
·
In early 70′s , C Programming was considered as High Level
language because it was capable of evaluating expressions,parenthesis
recursive functions etc.
·
Nowadays C may be considered as “Low Level Language” by some
programmer because it lacks a large runtime-system (no garbage collection, etc.)
Execution Models of HLL :
1. Interpreted :
1. Interpreted languages are
read and then executed directly, with no compilation stage.
2. Program is read line by line
and convert it into machine code, and executes it. [More Info : Interpreter]
2. Compiled :
Languages are transformed into an executable form before running
There are two types of compilation:
2.1 Machine code
generation
Some compilers compile source code directly into machine code.
Machine code is generated by using compiler it is called as “truly compiled”
languages.
2.2 Intermediate
representations
Language is converted into middle level language and further
optimized and reused.
3. Translated :
1. A language may be translated
into a lower-level programming language for which native code compilers are
already widely available.
2. The C programming language is
a common target for such translators.
Some High Level Languages :
1. Ada
2. Algol
3. LISP
4. Pascal
5. Prolog.
6. Java
7. C#
Single Line Comment
Comments are non-executable code used to provide documentation to
programmer. Single Line Comment is used to comment out just Single
Line in the Code. It is used to provide One Liner Description of line.
Some ImportatntPoints :
1. Single Line Comment Can be Placed
Anywhere
2. Single Line Comment Starts
with ‘//’
3. Any Symbols written after
‘//’ are ignored by Compiler
4. Comment cannot hide
statements written before ‘//’ and On the Successive new line
Live Example :
#include<stdio.h>
void main()
{
printf("Hello"); //Single Line Comment
printf("By");
}
Which Part is Ignored by Compiler ?
[Shown by Asterisk]
#include<stdio.h>
voidmain()
{
printf("Hello");// ********** Until Line Ends *****
printf("By");
}
Explanation :
1. In the above code we have
included Single Line Comment. Single Line Comment can be used anywhere in the
code.
2. Single Line Comment ignores
the complete line from the position where it has been written.Therefor Single
line comment is written usually after termination of statement.
3. For Multiple Line Comment we have another approach.Learn More on Difference between Single
Line and Multiple Line Comment.
Different Ways of Writing Singular
Line Comment :
For Specifying Operation
#include<stdio.h>
intmain()
{
intcvar=1,dvar=2;// Declare Variables
int sum =0;// Declare Sum
sum=cvar+dvar;// Compute Sum
printf("Sum : %d",sum);
return(0);
}
We can use this type of comment to specify the operation that we
are performing or to specify the formula used.
Multi Line Comment
·
Multi Line Comment Can be Placed Anywhere.
·
Multi Line Comment Starts with ‘/*’ .
·
Multi Line Comment Ends with ‘*/’ .
·
Any Symbols written between ‘/*’ and ‘*/’ are
ignored by Compiler.
·
It can be split over multiple Lines
Chapter 3 : Variables and Constants
C Tokens Chart
·
In C Programming punctuation,individualwords,charactersetc
are called tokens.
·
Tokens are basic building blocks of C Programming
Example :
No
|
Token Type
|
Example 1
|
Example 2
|
1
|
Keyword
|
do
|
while
|
2
|
Constants
|
number
|
sum
|
3
|
Identifier
|
-76
|
89
|
4
|
String
|
HTF”
|
PRIT”
|
5
|
Special Symbol
|
*
|
@
|
6
|
Operators
|
++
|
/
|
Basic Building Blocks and Definition
:
Token
|
Meaning
|
Keyword
|
A variable is a
meaningful name of data storage location in computer memory. When using a
variable you refer to memory address of computer
|
Constant
|
Constants are
expressions with a fixed value
|
Identifier
|
The term
identifier is usually used for variable names
|
String
|
Sequence of
characters
|
Special Symbol
|
Symbols other
than the Alphabets and Digits and white-spaces
|
Operators
|
A symbol that
represent a specific mathematical or non mathematical action
|
What is Variable in C Programming
Variable in C Programming is
also called as container to store the data. Variable name may have different
data types to identify the type of value stored. Suppose we declare variable of
type integer then it can store only integer values.Variable is considered as
one of the building block of C
Programming which is also called as identifier.
A Variable is a name given to
the memory location where the actual data is stored.
Consider real time example , suppose we need to store water then
we can store water in glass if quantity of water is small and Bucket is the
quantity of water is large. And big can to store water having quantity larger
than bucket similarly Variable (i.e Value container) may have different size
for storing different verities of values.
Fundamental Attributes of C Variable
:
1. Name of a Variable
2. Value Inside Variable
3. Address of Variable
4. Size of a Variable
5. Type of a Variable
1.Name of Variable
·
We can Give proper name to any Variable which is human readable.
·
Compiler won’t understand this name , This is only for human
understanding.
·
Variable name is only the name given to the “Memory address”.
·
Variable name maps into “Address inside” and then by considering
mapped address compiler processes data.
·
We have declared variable means “We have created one empty container which will hold data“.
2.Value inside Variable
·
Depending on the type of Variable we can store any value of
appropriate data type inside Variable.
·
Suppose we have “Integer
Variable” then Value inside variable will be of type “Integer“.
·
Simple Variable can only hold one value at a time.
3.Address of Variable
·
Variable can hold data ,it means there should be a container.
·
So container must have Starting Address.
·
Address of variable = Starting Address of Memory where Memory is
allocated to Variable.
4.Type of Variable
·
While declaring a variable we have to specify type of variable.
·
Type of variable tells compiler that – “Allocate memory for data of Specified type“.
·
If we declare variable of type Integer then compiler will allocate
memory container of size 2 bytes and container will be
able to store integer data only.
5.Size of Variable
·
We can use sizeof operator to calculate size of any data type.
Variable attributes
Variable Name
|
ivar
|
Variable Type
|
Integer
|
Variable Address
|
2000
|
Variable Size
|
2 Bytes
|
Variable Value
|
34
|
What is Local Variable ?
1. Local Variable is Variable
having Local Scope.
2. Local Variable is accessible
only from function or block in which it is declared .
3. Local variable is given
Higher Priority than the Global Variable.
Above Fig. Tells us that – Above Program has 2 blocks i.e
Inner Block and Outer Block
Facts about Local Variable :
1. Variables declared inside
outer block are visible or meaningful only inside outer block.
o Example : var1 is Local to Outer Block.
o var1 cannot be accessed from
its outer block.
o var1 cannot
be accessed from Other
Function or other block
o var1 can be
accessed from inner
block
2. Similarly Variables declared
inside inner block are visible or meaningful only inside Inner block.
3. Variables declared inside
inner block are not accessed by outer block .i.e
#include<stdio.h>
voidmain()
{
int var1=10;
{
int var2 =20;
printf("%d%d",var1,var2);// Legal : var1 can be accessed
}
printf("%d%d",var1,var2);// Error : var2 is not declared
}
Short Summary :
Inner Block can access
variables declared inside Outer Block
Outer block can’t access
variables declared inside Inner Block
Global Variable :
1. Global
Variable is Variable that is Globally available.
2. Scope of
Global variable is throughout the program [ i.e in all functions
including main() ]
3. Global
variable is also visible inside function , provided that it should not be
re-declared with same name inside function because … “High Priority is given
to Local Variable than Global“
4. Global
variable can be accessed from any function.
#include<stdio.h>
intvar=10;
void message();
voidmain()
{
intvar=20;
{
intvar=30;
printf("%d",var);
}
printf("%d",var);
message();
}
void message()
{
printf("%d",var);
}
Output :
30
20 10
·
Inside message() ‘var’ is not declared so global version of ‘var’
is used , so 10 will be printed.
{ intvar = 30;
printf("%d ",var); }
·
Here variable is re-declared inside block , so Local version is
used and 30 will be printed.
In Short -
1. For Inner
Block variables declared in Outer Block acts as “Global Variable“.
2. If block
contain undefined variable then -
o It checks
occurrence of that variable in outer block .
o If it is
also undefined in outer block then global version is
used .
o If it
also undeclared globally then its extern definition is checkedif not found
then it throws error.
Rules For Constructing Variable Name
1. Characters Allowed :
o Underscore(_)
o Capital Letters ( A – Z )
o Small Letters ( a – z )
o Digits ( 0 – 9 )
2. Blanks & Commas are not allowed
3. No Special Symbols other
than underscore(_) are allowed
4. First Character should be alphabet or Underscore
5. Variable name Should not
be Reserved Word
Explanation with Example
Tip 1 : Use allowed Characters
Valid Names
num
Num
Num1
_NUM
NUM_temp2
Tip 2 : blanks are not allowed
Invalid Names
number1
num1
addition of program
Tip 3 : No special symbols other that underscore
Valid Identifier
num_1
number_of_values
status_flag
Tip 4 : First Character must be underscore or Alphabet
Valid Identifier
_num1
Num
Num_
_
__
Invalid Identifier
1num
1_num
365_days
Tip 5 : Reserve words are not allowed
·
C is case sensitive.
·
Variable name should not be Reserve word.
·
However if we capitalize any Letter from Reserve word then it will
become legal variable name.
Valid Identifier
iNt
Char
Continue
CONTINUE
Invalid Identifier
int
char
continue
Tip 6 : Name of Identifier cannot be global identifier
Basic Note :
·
Global predefined macro starts with underscore. (_) .
·
We cannot use Global predefined macro as our function name.
Example : Some of the predefined
macros in C
·
__TIME__
·
__DATE__
·
__FILE__
·
__LINE__
Valid Identifier
__NAME__
__SUM__
Invalid Identifier
__TIME__
__DATE__
__FILE__
Tip 7 : Name of identifier cannot be register Pseudo variables
Invalid Example :
#include<stdio.h>
intmain(){
longint _AH =15;
printf("%ld",_AH);
return0;
}
Tip 8 : Name of identifier cannot be exactly same as of name of
another identifier within the scope of the function
Valid Example :
#include<stdio.h>
intmain(){
intivar=15;
{
intivar=20;
printf("%d",ivar);
}
return0;
}
Invalid Example : We cannot
declare same variable twice within same scope
#include<stdio.h>
intmain(){
intivar=15;
intivar=20;
printf("%d",ivar);
return0;
}
Tip 9 : Constants
1. We know that M_PI constant is
declared inside math.h header file.
2. Suppose in our program we
have declared variable M_PI and we have not included math.h header file then it
is legal variable.
Legal Example :
#include<stdio.h>
intmain(){
int M_PI=25;
printf("%d",M_PI);
return0;
}
Output :
25
Illegal Example :
#include<stdio.h>
#include<math.h>
intmain(){
int M_PI=25;
printf("%d",M_PI);
return0;
}
Output :
Compile error
Remember following Tricks
1. Do not Create
unnecessarily long
variable name
2. Do not use underscore as first character to
avoid confusion between System Variable & user defined variables because
many system variables starts with undescore
3. Variable names are case-Sensitive .i.e sum,Sum,SUM these all
three are different variable names.
4. Reserve words with one/more Capital
letters allowed eg. Int,Float,chAr are
allowed but try to skip them.
What is Constant ?
Constant in C means the content whose value does not change at the
time of execution of a program.
Definition :
Constant means “Whose
value cannot be changed“
Explanation :
·
Initially 5 is Stored in memory location and name x is given to it
·
After We are assigning the new value (3) to the same memory
location
·
This would Overwrite
the earlier value 5 since
memory location can hold only one value at a time
·
The value of ’3′,’5′ do not change ,so they are constants
·
In Short the ‘Values of Constant
Does not Change‘.
Different Types of C Constants :
Constant
|
Type of Value Stored
|
Integer Constant
|
Constant which stores
integer value
|
Floating Constant
|
Constant which stores float
value
|
Character Constant
|
Constant which stores
character value
|
String Constant
|
Constant which stores
string value
|
How to Declare Constant in C :
We can declare constant using
const variable. Suppose we need to declare
constant of type integer then we can have following two ways to declare it -
constint a =1;
intconst a =1;
above declaration is bit confusing but no need to worry, We can
start reading these variables from right to left. i.e
Declaration
|
Explanation
|
constint a =1; |
read as “a is an integer which is constant”
|
intconst a =1; |
read as “a is a constant integer”
|
Keywords in C Programming Language :
1. Keywords are those words
whose meaning is already defined by Compiler
2. Cannot be used as Variable
Name
3. There are 32
Keywords in C
4. C Keywords are also called as Reserved
words .
32 Keywords in C Programming
Language
auto
|
double
|
int
|
struct
|
break
|
else
|
long
|
switch
|
case
|
enum
|
register
|
typedef
|
char
|
extern
|
return
|
union
|
const
|
float
|
short
|
unsigned
|
continue
|
for
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signed
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void
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default
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goto
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sizeof
|
volatile
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do
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if
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static
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while
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Simple Tip :
We cannot Use Keywords for –
For Declaring Variable Name,For Function Name and for declaring Constant
Variable
C - Decision Making
Decision making structures require that the
programmer specify one or more conditions to be evaluated or tested by the
program, along with a statement or statements to be executed if the condition
is determined to be true, and optionally, other statements to be executed if
the condition is determined to be false.
Following is the general from of a typical
decision making structure found in most of the programming languages:
Statement
|
Description
|
An if
statement consists of a
boolean expression followed by one or more statements.
|
|
An if
statement can be followed
by an optional else
statement, which executes when the boolean expression is false.
|
|
You can use one if or else
if statement inside another if or else
if statement(s).
|
|
A switch statement allows a variable to be
tested for equality against a list of values.
|
|
You can use one swicth statement inside another switchstatement(s).
|
The ? :
Operator:
We
have covered conditional
operator ? : in previous
chapter which can be used to replace if...elsestatements.
It has the following general form:
Exp1?Exp2:Exp3;
Where Exp1, Exp2, and Exp3
are expressions. Notice the use and placement of the colon.
The value of a ?expression is
determined like this: Exp1 is evaluated. If it is true, then Exp2 is evaluated
and becomes the value of the entire ?expression. If Exp1 is false, then Exp3 is
evaluated and its value becomes the value of the expression.
If Statement :
This is
a conditional statement used in C to check condition or to control the flow of
execution of statements. This is also called as 'decision making statement or
control statement.' The execution of a whole program is done in one direction
only.
Syntax:
if(condition)
{
statements;
}
In
above syntax, the condition is checked first. If it is true, then the program
control flow goes inside the braces and executes the block of statements
associated with it. If it returns false, then program skips the braces. If
there are more than 1 (one) statements in if statement then use { } braces else
it is not necessary to use.
Program :
/* Program to demonstrate if statement.*/
#include <stdio.h>
#include <conio.h>
void main()
{
int a;
a=5;
clrscr();
if(a>4)
printf("\nValue of A is greater than 4 !");
if(a==4)
printf("\n\n Value of A is 4 !");
getch();
}
Output :
Value of A is greater than 4 !_
If-Else Statement :
This
is also one of the most useful conditional statement used in C to check
conditions.
Syntax:
if(condition)
{
true statements;
}
else
{
false statements;
}
In
above syntax, the condition is checked first. If it is true, then the program
control flow goes inside the braces and executes the block of statements
associated with it. If it returns false, then it executes the else part of a
program.
Program :
/* Program to demonstrate if-else statement.*/
#include <stdio.h>
#include <conio.h>
void main()
{
int no;
clrscr();
printf("\n Enter Number :");
scanf("%d",&no);
if(no%2==0)
printf("\n\n Number is even !");
else
printf("\n\n Number is odd !");
getch();
}
Output :
Enter Number : 11
Number is odd !_
Nested If-Else Statement :
It is
a conditional statement which is used when we want to check more than 1
conditions at a time in a same program. The conditions are executed from top to
bottom checking each condition whether it meets the conditional criteria or
not. If it found the condition is true then it executes the block of associated
statements of true part else it goes to next condition to execute.
Syntax:
if(condition)
{
if(condition)
{
statements;
}
else
{
statements;
}
}
else
{
statements;
}
In
above syntax, the condition is checked first. If it is true, then the program
control flow goes inside the braces and again checks the next condition. If it
is true then it executes the block of statements associated with it else
executes else part.
Program :
/* Program to demonstrate nested if-else statement.*/
#include <stdio.h>
#include <conio.h>
void main()
{
int no;
clrscr();
printf("\n Enter Number :");
scanf("%d",&no);
if(no>0)
{
printf("\n\n Number is greater than 0 !");
}
else
{
if(no==0)
{
printf("\n\n It is 0 !");
}
else
{
printf("Number is less than 0 !");
}
}
getch();
}
Output :
Enter Number : 0
It is 0 !_
Switch case Statement :
This is a multiple or multiwaybrancing decision making
statement.
When we use nested if-else statement to check more than 1
conditions then the complexity of a program increases in case of a lot of
conditions. Thus, the program is difficult to read and maintain. So to overcome
this problem, C provides 'switch case'.
Switch case checks the value of a expression against a case
values, if condition matches the case values then the control is transferred to
that point.
A switch statement allows a variable to be
tested for equality against a list of values. Each value is called a case, and
the variable being switched on is checked for each switch case.
Syntax:
The
syntax for a switch statement in C programming language is
as follows:
switch(expression){
case constant-expression :
statement(s);
break;/* optional */
case constant-expression :
statement(s);
break;/* optional */
/* you can have any number of case statements */
default:/* Optional */
statement(s);
}
The
following rules apply to a switch statement:
·
The expression used in a switch statement must have an integral or
enumerated type, or be of a class type in which the class has a single
conversion function to an integral or enumerated type.
·
You can have any number of case statements within a switch. Each
case is followed by the value to be compared to and a colon.
·
The constant-expression for a case must be the same data type
as the variable in the switch, and it must be a constant or a literal.
·
When the variable being switched on is equal to a case, the
statements following that case will execute until a break statement is reached.
·
When a break statement is reached, the switch
terminates, and the flow of control jumps to the next line following the switch
statement.
·
Not every case needs to contain a break. If no break appears, the flow of control will fall throughto subsequent cases
until a break is reached.
·
A switch statement can have an optional default case, which must appear at the end of
the switch. The default case can be used for performing a task when none of the
cases is true. Nobreak is
needed in the default case.
Flow
Diagram:
Example:
#include<stdio.h>
int main ()
{
/* local variable definition */
char grade ='B';
switch(grade)
{
case'A':
printf("Excellent!\n");
break;
case'B':
case'C':
printf("Well done\n");
break;
case'D':
printf("You passed\n");
break;
case'F':
printf("Better try again\n");
break;
default:
printf("Invalid grade\n");
}
printf("Your grade is %c\n", grade );
return0;
}
When the above code is
compiled and executed, it produces following result:
Well done
Your grade is B
Program :
/* Program to demonstrate switch case statement.*/
#include <stdio.h>
#include <conio.h>
void main()
{
int no;
clrscr();
printf("\n Enter any number from 1 to 3 :");
scanf("%d",&no);
switch(no)
{
case 1:
printf("\n\n It is 1 !");
break;
case 2:
printf("\n\n It is 2 !");
break;
case 3:
printf("\n\n It is 3 !");
break;
default:
printf("\n\n Invalid number !");
}
getch();
}
Output 1
:
Enter any number from 1 to 3 : 3
It is 3 !_
Output 2
:
Enter any number from 1 to 3 : 5
Invalid number !_
* RULES FOR DECLARING SWITCH CASE :
·
The case label should be integer or character constant.
·
Each compound statement of a switch case should contain break
statement to exit from case.
·
Case labels must end with (:) colon.
* ADVANTAGES OF SWITCH CASE :
·
Easy to use.
·
Easy to find out errors.
·
Debugging is made easy in switch case.
·
Complexity of a program is minimized.
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