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

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

Non zero = True

zero means false

Zero = False

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

int a,b,c;

This statement declares the variables a,b and c as integers.

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 logical.c -o log

Type

./log

gcc logical.c -o log

For executing the code type

./log

Press Enter.

Enter the values of a,b and c

I will enter the values as,

0

34

567

The output is displayed as,

c is greatest.

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.

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 -o log1

to execute the program type

./log1

press Enter.

Enter the values of a,b and c

I will enter the values as

0

34

567

We see the output is similar to the C program.

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

Let's switch 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))

eg. (a == 0 || b == 0 || c == 0)

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

Hint: (a != b)

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