Module X: Additional Materials - Algoritma-dan-Pemrograman-ITS/DasarPemrograman GitHub Wiki

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Bitwise Operators

Bitwise operators, like the name, are used to perform operations on two operands in a binary scale (base 2 numbers). Before learning further about how bitwise operations work, it's better that we understand binary numbers.

There are 6 bitwise operators: AND, OR, XOR, COMPELEMENT, SHIFT LEFT, and SHIFT RIGHT. Let's look at the table below to understand their differences.

Operator Symbol Details
Bitwise AND & Evaluates two operands per bit. Results in 1 if both operand bits are 1, otherwise results in 0.
Bitwise OR | Evaluates two operands per bit. Results in 1 if one or more operand bits are 1, otherwise results in 0.
Bitwise XOR ^ Evaluates two operands per bit. Results in 1 if both operand bits are different, otherwise results in 0.
Bitwise COMPLEMENT ~ Inverses all bit values, 1 to 0 and 0 to 1 (in bit length).
Bitwise SHIFT LEFT << Shift bits to the left for as many as n (second operand).
Bitwise SHIFT RIGHT >> Shift bits to the right for as many as n (second operand).

Bitwise operators examples:

Suppose we have the numbers 12 and 5. In binary, 12 is represented as (1100) and 5 as (0101). The bitwise operations for these numbers are as follows.

  • Bitwise AND

    12 = (1100)
 5 = (0101)
------------ &
 4 = (0100)

  • Bitwise OR

    12 = (1100)
 5 = (0101)
------------ | 
13 = (1101)

  • Bitwise XOR

    12 = (1100)
 5 = (0101)
------------ ^
 9 = (1001)

  • Bitwise COMPLEMENT

     12 = (1100)
~12 = (0011)

  • Bitwise SHIFT LEFT

    Suppose we want to shift the bits of 13 to the left as many as 2, then the expression is 13 << 2.

         13 = (001101)
13 << 2 = (110100)

    Notice that the rightmost bit, after the left shifts, will be filled with 0's. Therefore the result of 13 << 2 = 52.

  • Bitwise SHIFT RIGHT

    Now, suppose we want to shift the bits of 13 to the right as many as 2, then the expression is 13 >> 2.

         13 = (001101)
13 >> 2 = (000011)

    Notice that the leftmost bit, after the right shifts, will be filled with 0's. Therefore the result of 13 >> 2 = 3.

sizeof() Operator

Although its form is more similar to a function, in the standardization of the C programming language it is an operator. The use of this operator is to find out the size of memory allocated by an operand (can be a variable or a data type) in bytes.

Example:

sizeof(int);

Address-of Operator (&)

This operators returns the memory address of an operand (variable).

Example:

int var;
scanf("%d\n", &var);

Dereference Operator (*)

Contrary to the address-of operator (&), dereference operator (*) returns the value of a pointer variable (this will be further explained in a later module on Pointers).

Although it uses the same symbol as a multiplier, dereference operator has a totally different function than the multiplier.

Conditional Operator (? :)

Conditional operator is the only ternary operator (works on three operands) in C. Its function is similar to if - else statement (will be further explained in a later module on Branching).

Comma Operator (,)

The comma operator (,) in C is used as a binary operator when used in the same sequence as assignment. It will only consider the rightmost operand as the value to be assigned.

int number = (5, 23);   // number is equal to 23, not 5

Aside from functioning as an operator, the comma sign (,) is also used as a separator between statements. For instance when making declarations of more than one variable.

int var1, var2, var3;   
// Usage of the comma sign to separate the declaration of each variable

Not all statements can be separated by the comma sign.

Subscript Operator ([])

It is most commonly used to access an array element (will be explained in a later module on Arrays).

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