Increment and Decrement Operators in C (original) (raw)

The increment ( ++ ) and decrement ( -- ) operators in C are unary operators for incrementing and decrementing the numeric values by 1, respectively.** They are one of the most frequently used operators in programming for looping, array traversal, pointer arithmetic, and many more.

**Increment Operator in C

The **increment operator ( ++ ) is used to increment the value of a variable in an expression by 1. It can be used on variables of the numeric type, such as integer, float, character, pointers, etc.

The Increment Operator in C can be used in two ways, either as a prefix (pre-increment) or a postfix (post-increment).

**Syntax:

C `

// AS PREFIX ++m

// AS POSTFIX m++

`

where m is variable. Both pre-increment and post-increment increase the value of the variable but there is a little difference in how they work.

1. Pre-Increment

In pre-increment, the increment operator is used as the prefix. Also known as prefix increment, the value is incremented first according to the precedence and then the less priority operations are done.

C `

result = ++var1;

`

The above expression can be expanded as

C `

var = var + 1; result = var;

`

2. Post-Increment

In post-increment, the increment operator is used as the suffix of the operand. The increment operation is performed after all the other operations are done. It is also known as postfix increment.

C `

result = var1++;

`

The above expression is equivalent

C `

result = var; var = var + 1;

`

**Example of Increment Operator

C `

#include <stdio.h>

void preincrement(int x) { // PREFIX printf( "X = %d\n", x); int prefix = ++x; printf("Prefix Increment: %d\n", prefix); }

void postincrement(int x) { // POSTFIX printf( "X = %d\n", x); int postfix = x++; printf("Postfix Increment: %d", postfix); }

int main() { int x =5; preincrement(x); postincrement(x);

return 0;

}

`

Output

X = 5 Prefix Increment: 6 X = 5 Postfix Increment: 5

As we can see in postfix, the value is incremented after the assignment operator is done.

**Note: The post-increment has higher precedence that pre-increment as it is postfix operator while pre-increment comes in unary operator category.

**Decrement Operator in C

The decrement operator is used to decrement the value of a variable in an expression. In the Pre-Decrement, the value is first decremented and then used inside the expression. Whereas in the Post-Decrement, the value is first used inside the expression and then decremented.

**Syntax

Just like the increment operator, the decrement operator can also be used in two ways:

C `

// AS PREFIX --m

// AS POSTFIX m--

`

where m is variable.

1. Pre-Decrement Operator

The pre-decrement operator decreases the value of the variable immediately when encountered. It is also known as prefix decrement as the decrement operator is used as the prefix of the operand.

C `

result = --m;

`

which can be expanded to

C `

m = m - 1; result = m;

`

2. Post-Decrement Operator

The post-decrement happens when the decrement operator is used as the suffix of the variable. In this case, the decrement operation is performed after all the other operators are evaluated.

C `

result = m--;

`

The above expression can be expanded as

C `

result = m; m = m-1;

`

**Example of Decrement Operator

C `

#include <stdio.h>

void predecrement(int x) { // PREFIX printf( "X = %d\n", x); int prefix = --x; printf("Prefix Decrement: %d\n", prefix); } void postdecrement(int x) { // POSTFIX printf( "X = %d\n", x); int postfix = x++; printf("Postfix Decrement: %d", postfix); }

// Driver code int main() { int x =5; predecrement(x); postdecrement(x);

return 0;

}

`

Output

X = 5 Prefix Decrement: 4 X = 5 Postfix Decrement: 5

**Increment vs Decrement

**The following table lists the major differences between increment and decrement operators in C :