Assignment Operators in C
In C language, the assignment operator stores a certain value in an already declared variable. A variable in C can be assigned the value in the form of a literal, another variable, or an expression.
The value to be assigned forms the right-hand operand, whereas the variable to be assigned should be the operand to the left of the ”=” symbol, which is defined as a simple assignment operator in C.
In addition, C has several augmented assignment operators.
The following table lists the assignment operators supported by the C language −
| Operator | Description | Example |
|---|---|---|
| = | Simple assignment operator. Assigns values from right side operands to left side operand | C = A + B will assign the value of A + B to C |
| += | Add AND assignment operator. It adds the right operand to the left operand and assign the result to the left operand. | C += A is equivalent to C = C + A |
| -= | Subtract AND assignment operator. It subtracts the right operand from the left operand and assigns the result to the left operand. | C -= A is equivalent to C = C - A |
| *= | Multiply AND assignment operator. It multiplies the right operand with the left operand and assigns the result to the left operand. | C *= A is equivalent to C = C * A |
| /= | Divide AND assignment operator. It divides the left operand with the right operand and assigns the result to the left operand. | C /= A is equivalent to C = C / A |
| %= | Modulus AND assignment operator. It takes modulus using two operands and assigns the result to the left operand. | C %= A is equivalent to C = C % A |
| <<= | Left shift AND assignment operator. | C <<= 2 is same as C = C << 2 |
| >>= | Right shift AND assignment operator. | C >>= 2 is same as C = C >> 2 |
| &= | Bitwise AND assignment operator. | C &= 2 is same as C = C & 2 |
| ^= | Bitwise exclusive OR and assignment operator. | C ^= 2 is same as C = C ^ 2 |
| |= | Bitwise inclusive OR and assignment operator. | C |= 2 is same as C = C | 2 |
Simple Assignment Operator (=)
The = operator is one of the most frequently used operators in C. As per the ANSI C standard, all the variables must be declared in the beginning. Variable declaration after the first processing statement is not allowed.
You can declare a variable to be assigned a value later in the code, or you can initialize it at the time of declaration.
You can use a literal, another variable, or an expression in the assignment statement.
int x = 10; // declaration with initialization
int y; // declaration
y = 20; // assignment later
int z = x + y; // assign an expression
int d = 3, f = 5; // definition and initializing d and f.
char x = 'x'; // the variable x has the value 'x'.
Once a variable of a certain type is declared, it cannot be assigned a value of any other type. In such a case the C compiler reports a type mismatch error.
In C, the expressions that refer to a memory location are called “lvalue” expressions. A lvalue may appear as either the left-hand or right-hand side of an assignment.
On the other hand, the term rvalue refers to a data value that is stored at some address in memory. A rvalue is an expression that cannot have a value assigned to it which means an rvalue may appear on the right-hand side but not on the left-hand side of an assignment.
Variables are lvalues and so they may appear on the left-hand side of an assignment. Numeric literals are rvalues and so they may not be assigned and cannot appear on the left-hand side. Take a look at the following valid and invalid statements −
int g = 20; // valid statement
10 = 20; // invalid statement
Augmented Assignment Operators
In addition to the = operator, C allows you to combine arithmetic and bitwise operators with the = symbol to form augmented or compound assignment operator. The augmented operators offer a convenient shortcut for combining arithmetic or bitwise operation with assignment.
Example 1
For example, the expression “a += b” has the same effect of performing “a + b” first and then assigning the result back to the variable “a”.
#include <stdio.h>
int main(){
int a = 10;
int b = 20;
a += b;
printf("a: %d", a);
return 0;
}
Output
Run the code and check its output −
a: 30
Example 2
Similarly, the expression “a <<= b” has the same effect of performing “a << b” first and then assigning the result back to the variable “a”.
#include <stdio.h>
int main(){
int a = 60;
int b = 2;
a <<= b;
printf("a: %d", a);
return 0;
}
Output
Run the code and check its output −
a: 240
Example 3
Here is a C program that demonstrates the use of assignment operators in C −
#include <stdio.h>
int main(){
int a = 21;
int c ;
c = a;
printf("Line 1 - = Operator Example, Value of c = %d\n", c );
c += a;
printf("Line 2 - += Operator Example, Value of c = %d\n", c );
c -= a;
printf("Line 3 - -= Operator Example, Value of c = %d\n", c );
c *= a;
printf("Line 4 - *= Operator Example, Value of c = %d\n", c );
c /= a;
printf("Line 5 - /= Operator Example, Value of c = %d\n", c );
c = 200;
c %= a;
printf("Line 6 - %%= Operator Example, Value of c = %d\n", c );
c <<= 2;
printf("Line 7 - <<= Operator Example, Value of c = %d\n", c );
c >>= 2;
printf("Line 8 - >>= Operator Example, Value of c = %d\n", c );
c &= 2;
printf("Line 9 - &= Operator Example, Value of c = %d\n", c );
c ^= 2;
printf("Line 10 - ^= Operator Example, Value of c = %d\n", c );
c |= 2;
printf("Line 11 - |= Operator Example, Value of c = %d\n", c );
return 0;
}
Output
When you compile and execute the above program, it will produce the following result −
Line 1 - = Operator Example, Value of c = 21
Line 2 - += Operator Example, Value of c = 42
Line 3 - -= Operator Example, Value of c = 21
Line 4 - *= Operator Example, Value of c = 441
Line 5 - /= Operator Example, Value of c = 21
Line 6 - %= Operator Example, Value of c = 11
Line 7 - <<= Operator Example, Value of c = 44
Line 8 - >>= Operator Example, Value of c = 11
Line 9 - &= Operator Example, Value of c = 2
Line 10 - ^= Operator Example, Value of c = 0
Line 11 - |= Operator Example, Value of c = 2