Lesson 3.11. Logical operators

Lesson 3.10 Summary Lesson 3.12

In lesson 3.5, we studied bitwise logical operators. The logical operations were then applied bit by bit. The logical operators studied in this course work according to the following rule:

An operand is considered false if its value is equal to zero ;
otherwise, it is true.

Here are some examples:

0 is faux
15 is true
12.5 is true
3<2 is false
'r' is true
...

There are three logical operators:

Operator	Name	Type
`&&`	logical AND	binary
`\|\|`	logical OR	binary
`!`	logical NOT	unary

As for the comparison operators, these operators can only return 0 or 1. The returned value is always of integer type (int).

These operators are mostly used to combine comparisons:

if (a<5 && a>10)
  ...

Quiz

For a logical operator, the value -5 is considered as ....

an integer

undetermined

logical false

logical true

Check

What should be the type of the variable x?

x = 1 || 0;

bool

char

int

float

Check Bravo! The type returned by the logical operators is always int

What is the bitwise logical operator AND?

& or &&

None of the other answers

Check Bravo! Do not confuse the bitwise logical operator & with the logical operator &&.

What does the following program display?

printf ("%d", 1565 || 0);

First we have to convert 1565 to binary

1565

Check

What does the following program display?

printf ("%d", (12 || 0) && 127);

127

Check

How to test if p is between 0 and 100 inclusive?

p<0 && p>100

p>=0 & p<=100

p>=0 && p<=100

p>=0 || p<=100

Check Bravo! p must be greater than 0 AND less than 100.

What is the equivalent instruction?

x = !(a<b);

x = a>b;

x = a>=b;

x = a<b;

x = a<=b;

Check Bravo! The operator ! inverts the logical proposition a<b.

Lesson 3.10 Summary Lesson 3.12

Lesson 3.11. Logical operators

Quiz

See also