So first we will learn about conditional
statements
In Conditional
statements we put a particular condition and depending on the output of the statement
that is true or false the decision regarding the execution of a particular set
of statement is done
There are two
conditional statements in C++
They are if and switch
if
The if statement has the same meaning as in English i.e. if this is
true then this otherwise that ok I understand you are not clear let us take an
example but before that let me tell you that along with if we have a else set
of statements also.
Syntax:
if(condition)
{
Statements
}
else
{
Statements
}
example
#include<iostream.h>
void main()
{
int a;
cout<<”enter value of a:”;
cin>>a;
if(a!=0)
{
cout<<”a is nonzero”;
}
}
Now as you can see first we enter the number a
and then the control comes to the if statements .here first the compiler checks
the condition if the condition is true i.e. a not = 0 then the statements under
the if braces are executed but if the condition is not true then the statements
under the if are not executed.
Let me now demonstrate the use of else
#include<iostream.h>
void main()
{
int a;
cout<<”enter the value of a:”;
cin>>a;
if(a!=0)
{
cout<<”a is non zero”;
}
else
{
cout<<”a is zero”;
}
}
In this program we use if and else together .when
the same condition as in the above program is encountered the compiler has to
make decision weather to execute the if statements or the else statements. Here
the decision is taken depending on the condition given if the condition is true
then the statements under if are
executed but if it is false the statements under else are executed.
The other conditional
statement is switch. It is use only on a limited
basis for some specific tasks. It is used to check a variable and depending
upon the value given it executes the statements corresponding to the value
entered .ok give me some time to explain. Take a look at its syntax first
Syntax;
switch(variable)
{
case 1:
Statements ;
break;
case 2:
Statements;
break;
Blah blah
blah
case n:
Statements;
break;
default:
Statements;
}
For example:
#include <iostream.h>
void main() {
cout << "enter the
choice";
int
s
cin>>s;
switch (s)
{
case 1:
cout
<< "Monday "
break;
case 2:
cout
<< "Tuesday "
break;
case 3:
cout
<< "Wednesday";
break;
default:
cout
<< "wrong choice "
}
}
As you can see, the case statements is executed if the case constant matches the
variable passed to switch, the default statement is executed if the variable does not match any
case constant .it is to be noted that break is actually not required in the
syntax of the switch but if we do not write break than the statement s
following the matched case constant will also be executed i.e. break only sends
the control to the end of the switch block. So you miss break and all
statements following the matched case are executed which may not produce error
but may harm the logic of the program entirely.
Note
To use the if statement you need
some operators.these operators are given
below
1. == stands for equality
operator checks weather the two numbers are true or not that’s
2. != stands for not equal to this
checks weather the two numbers are different or not
3. >, <, >=, <= stand for the greater, less, greater or equal to and less or
equal to operators, respectively.
4. && is the
logical and operator its working can be seen in the program blog.
5. || is the logical or operator.
6. ! is the logical not operator. It
negates
Precedence
For a complex statement consisting of a number of operators then
it becomes difficult for us to determine which operation will be executed first
and which after that. So here the precedence of operators play
a very important role. The precedence of operators is in the following order .It
goes on decreasing as we go down.
++ , -- (increment
and decrement operator)
* , /
,% (multiply, divide, modulus)
< , <=
, > ,
>= (less than, greater
than)
==
, != (equal, not equal)
&&
(logical and)
||
(logical or)
?:
(conditional expression)
= (assignment
operator)
We can also use parenthesis for specifying the operations to be
taken into consideration first and thereafter.
