Difference between revisions of "C-and-C++/C2/Logical-Operators/English"

• Logical Operators like
• Logical AND
  • Eg- expression1 && expression2
• Logical OR
  • Eg- expression1 || expression2
• Logical NOT
  • Eg- !(expression1)

• We will do these with the help of examples.

Ubuntu 11.10 as the operating system

gcc and g++ Compiler version 4.6.1 on Ubuntu.

Non zero = True

Zero = False

In C and C++, true is any value, other than 0.

Non-zero means true.

Zero means false

Expressions using logical operators return 1 for true and 0 for false.

int a,b,c;

printf("Enter the values of a,b

and c \n");

scanf("%d %d %d", &a, &b,

&c);

if((a > b) && (a > c))

printf("a is greatest \n");

To compare simultaneously, we use the logical AND operator.

Here, all of the conditions have to be true for logical AND to return a true value.

The expression is not evaluated further on encountering a false condition.

So, the expression (a>c) is evaluated only if (a>b) is true.

If a is less than b, then the expression won't be evaluated further.

This statement is be evaluated if the previous condition is true.

else if (b > c)

printf("b is greatest \n");

else

printf("c is greatest \n");

if(a == 0 || b == 0 || c == 0)

Here, any one of the conditions has to be true for logical OR to return a true value.

The expression is not evaluated further on encountering a true condition.

So, if a == zero, then the remaining two expressions won't be evaluated.

printf("The product of a, b

and c is zero \n");

return 0;

}

return 0 and ending curly bracket.

Save it with extension .c

I have saved my file as logical.c

gcc space logical.c space -o space log Press Enter

Type

./log Press Enter

gcc space logical.c space -o space log

Press Enter.

To execute, type ./log

Press Enter.

The output is displayed as here,

c is greatest.

And The product of a, b and c is zero.

You should try executing this program with different sets of inputs.

Here is the code in C++.

#include <iostream>

using namespace std;

int main()

{

int a,b,c;

cout <<"Enter the values of a,b

and c \n";

cin >>a >>b >>c;

if((a > b) && (a > c))

cout <<"a is greatest \n";

else if (b > c)

cout <<"b is greatest \n";

else

cout <<"c is greatest \n";

if(a == 0 || b == 0 || c == 0)

cout <<"The product of a, b and

c is zero \n";

return 0;

}

There's a change in the header file.

The using statement has been used.

Also there is a difference in output and input statements.

The operators behave in the same way as they did in C.

point to .cpp

Make sure the file is saved with extension .cpp

g++ logical.cpp -o log

to execute

./log

g++ logical.cpp space -o space log1

Press Enter.

To execute, type

./log1

Press Enter.

So we see the output is similar to the C program.

You should try executing this program with different sets of inputs too.

Let us switch back to the editor.

if(a > b) && (a > c)

Delete this and this.

Come back to the terminal.

Compile and execute as before.

Expected identifier before '(' token.

We have to evaluate them as one expression using AND operator.

Click on Save.

Come back to the terminal.

So, it is working now.

Let us now summarize the tutorial.

• && Logical AND
  • eg. ((a > b) && (a > c))
• || Logical OR
  • eg. (a == 0 || b == 0 || c == 0)

Write a program that takes two numbers as input from the user.

Check whether the two numbers are equal or not using NOT operator.

Hint: (a != b)

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