Increment & Decrement operators

'C' has two very useful operators not generally found in other languages. They are increment and decrement operators ++ and --.

The operator ‘++’ adds 1 to the variable, while ‘--‘subtracts 1. Both the operators are unary operators & the fallowing form.

Increment & Decrement operators
a++ (post increment)	a-- (post decrement)
++a (pre increment)	--a (pre decrement)

++a or a++	++a --> a=a+1
--a or a--	--a --> a=a-1

While ++a & a-- mean something when form statements independently.

Example:-

Let a=5, b=a++ (post increment)	Let a = 5, b = ++a (pre increment)
b=5, a=a+1 --> 5+1=6	b=++a --> 5+1=6
b=5, a=6	a=6, b=6

They behave differently when they are used in expressions from the right hand side of assignment statements. 

In the 1st case, a post fix operators 1st assigns the value to the variable on left & the increments the operator. In the 2nd case a prefix operator 1st adds 1 to the operator & then the result is assigned to the variable on left.

Increments operators
a=10, b=a++	b=10	a=11
a=10, b=++a	b=11	a=11
a=10, b=a++ + a++	b=20	a=12
a=10, b=a++ + ++a	b=22	a=12
a=10, b=++a + a++	b=22	a=12
a=10, b=++a + ++a	b=24	a=12
a=10, b=a++ + a++ + a++	b=33	a=13
a=10, b=a++ + a++ + ++a	b=34	a=13
a=10, b=a++ + ++a + ++a	b=35	a=13
a=10, b=++a + a++ + a++	b=34	a=13
a=10, b=++a + a++ + ++a	b=35	a=13
a=10, b=++a + ++a + a++	b=35	a=13
a=10, b=++a + ++a + ++a	b=36	a=13

Decrements operators
a=10, b=a--	b=10	a=9
a=10, b=--a	b=9	a=9
a=10, b=a-- + a--	b=19	a=8
a=10, b=a-- + --a	b=18	a=8
a=10, b=--a + a--	b=18	a=8
a=10, b=--a + --a	b=17	a=8
a=10, b=a-- + a-- + a--	b=27	a=7
a=10, b=a-- + a-- + --a	b=27	a=7
a=10, b=a-- + --a + a--	b=27	a=8
a=10, b=a-- + --a + --a	b=25	a=7
a=10, b=--a + a-- + a--	b=27	a=7
a=10, b=--a + a-- + --a	b=24	a=7
a=10, b=--a + --a + a--	b=25	a=7
a=10, b=--a + --a + --a	b=24	a=7
a=10, b=a++ - a++ - a++	b=-10	a=-13
a=10, b=a++ - ++a – a++	b=-11	a=-13
a=10, b=a++ - --a + a++	b=10	a=11