Need of logical operators:
Some times multiple conditions need to be checked to test a
possibility.
Logical operators are used to concatenate multiple
relational expressions in order to take a logical decision.
Logical operators:
Logical operator | Meaning |
&& | AND logical operator |
|| | OR logical operator |
! | Not logical operator |
It is a logical operator used to concatenate multiple
relational expressions to take a logical decision.
The "AND" logical expression gives true if all the
relational expressions are true, returns false if any one of the condition is
false.
It is represented with a series electrical circuit.
Truth table of AND logical operator:
|
A |
B |
A&&B |
|
1 |
1 |
1 |
|
1 |
0 |
0 |
|
0 |
1 |
0 |
|
0 |
0 |
0 |
Example1:
 |
Example2:
 |
|| (OR logical operator)
It is a logical operator used to concatenate multiple
relational expressions to take a logical decision.
The "OR" logical expression gives false if all the
relational expressions are false, returns true if any one of the condition is true.
It is represented with a parallel electrical circuit.
Truth table of OR logical operator:
 |
|
A |
B |
A||B |
|
1 |
1 |
1 |
|
1 |
0 |
1 |
|
0 |
1 |
1 |
|
0 |
0 |
0 |
Example1:
 |
Example2:
 |
! (NOT logical operator):
It gives a negation of an expression.
|
A |
!A |
|
1 |
0 |
|
0 |
1 |
Example1:
Priority of operators so far:
|
Operators |
Priority/Presidency |
|
( ) |
1 |
|
! |
2 |
|
* / % |
3 |
|
+ - |
4 |
|
< > <=
>= |
5 |
|
== != |
6 |
|
&& |
7 |
|
|| |
8 |
|
= |
9 |
Spcification1:
Accept any four digit number and print whether the number is
a palindrome number or not.
|
#include<stdio.h>
void main()
{
int n,first,second,third,fourth;
printf("Enter any four digit number:");
scanf("%d",&n);
fourth=n%10;
n=n/10;
third=n%10;
n=n/10;
second=n%10;
n=n/10;
first=n%10;
if(first==fourth && second==third)
printf("Palindrome number");
else
printf("Not a palindrome number");
}
Execution1:
Enter any four digit number: 2332
Palindrome number
Execution2:
Enter any four digit number: 2342
Not a palindrome number
Specification2:
Accept any number and print whether the number is a single
digit number or not.
Program:
#include<stdio.h>
void main()
{
int n;
printf("Enter any number:");
scanf("%d",&n);
if(n>=-9 && n<=9)
printf("Single digit number");
else
printf("Not a single digit number");
}
Execution1:
Enter any number: -8
Single digit number
Execution2:
Enter any number: 5
Single digit number
Execution3:
Enter any number: 45
Not a single digit number
Specification3:
Accept the marks of a student in 3 subjects and print
whether pass or fail. The condition for pass is getting 50 marks in every
subject.
Program:
#include<stdio.h>
main()
{
int math,physics,chemistry;
printf("Enter the marks in Math, Physics and chemistry..\n");
scanf("%d%d%d",&math,&physics,&chemistry);
if(math>=35)
printf("he is pass in math");
else
printf("he is fail in math");
if(physics>=35)
printf("he is pass in physics");
else
printf("he is fail in physics");
if(chemistry>=35)
printf("he is pass in chemistry");
else
printf("he is fail in chemistry");
}
Execution1:
Enter the mark in Math, Physics and chemistry…
60 80 92
Pass
Execution2:
Enter the mark in Math, Physics and chemistry…
52 86 12
Fail
Specification4:
Accept any alphabet and print whether the alphabet is a
vowel or consonant.
Program:
#include<stdio.h>
void main()
{
char ch;
printf("Enter any alphabet:");
scanf("%c",&ch);
/* We can also check capitals */
if(ch==’a’ || ch==’e’ || ch==’i’ || ch==’o’ || ch==’u’)
printf("Vowel");
else
printf("Consonant");
}
Execution1:
Enter any alphabet: e
Vowel
Execution2:
Enter any alphabet: p
Consonant
Specification5:
Accept the gender, age, percentage of marks of a person and
print whether selected or not. Here selection criteria are that, a first class
male with the age between 25 and 34.
Program:
#include<stdio.h>
void main()
{
int age;
float percent;
char gender;
printf("Enter the gender m/f :");
scanf("%c",&gender);
printf("Age:");
scanf("%d",&age);
scanf("%f",&percent);
if(gender==’m’ && percent>=60 && age>=25 && age<=34)
printf("Selected");
else
printf("Not selected");
}
class="MsoNormal">
Execution1:
Enter the gender m/f : m
Age: 30
Enter the percentage in qualifying exam: 75
Selected
Execution2:
Enter the gender m/f : f
Age: 34
Enter the percentage in qualifying exam: 54
Not selected
Specification6:
Accept gender and age of person and print whether major or
minor.
Logic: Male should have 21 years and female must have 18
years to become majors.
Program:
#include<stdio.h>
void main()
{
int n;
printf("Enter any number:");
scanf("%d",&n);
if(n>=-9 && n<=9)
printf("Sigle digit number");
if((n>=-99&&n<=10) || (n>=10&&n<=99))
printf("Two digit number");
if((n>=-999&&n<=-100) || (n>=100&&n<=999))
printf("Three digit number");
if(n>999)
printf("Biggest number");
if(n<-999 code="" mallest="" number="" printf="">Execution1:
Enter the gender m/f: m
Enter the age: 27
Major
Execution2:
Enter the gender m/f: f
Enter the age: 20
Major
Execution3:
Enter the gender m/f: m
Enter the age: 15
Minor
Specification7:
Accept any number and print whether the given number is a
two digit number or not.
Logic:
 |
Program:
#include<stdio.h>
void main()
{
int n;
printf("Enter any number:");
scanf("%d",&n);
if((n>=-99&&n<=-10)||(n>=10&&n<=99))
printf("Two digit number");
else
printf("Not a two digit number");
}
Execution1:
Enter any number: -50
Two digit number
Execution2:
Enter any number: 55
Two digit number
Execution3:
Enter any number: 9
Not a two digit number
Specification8:
Accept any number and print whether the number is a single
digit, two digit, three digit, biggest or smallest number.
Logic:
 |
Here we got more than two possibilities, hence we cannot
solve the problem with if-else rather we use simple if
Simple if is capable to test any number possibilities.
Program:
#include<stdio.h>
void main()
{
int n;
printf("Enter any number:");
scanf("%d",&n);
if(n>=-9 && n<=9)
printf("Sigle digit number");
if((n>=-99&&n<=10) || (n>=10&&n<=99))
printf("Two digit number");
if((n>=-999&&n<=-100) || (n>=100&&n<=999))
printf("Three digit number");
if(n>999)
printf("Biggest number");
if(n<-999 code="" mallest="" number="" printf="">Execution1:
Enter any number: 256
Three digit number
Execution2:
Enter any number: -25
Two digit number
Execution3:
Enter any number: 5
Single digit number
Execution4:
Enter any number: 2256
Biggest number
Execution5:
Enter any number: -1000
Smallest number
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