[Learnbyexamples]

The built-in ++ and operators can appear on both sides of their operand:

Code:

int n=0;  
++n; /*prefix*/  
n++; /*postfix*/

You probably know that a prefix operator first changes its operand before taking its value. For example:

Code:

int n=0, m=0;  
n = ++m; /*first increment m, then assign its value to n*/  
cout << n << m; /* display 1 1*/

In this example, n equals 1 after the assignment because the increment operation took place before m's value was taken and assigned to n. By contrast,

Code:

int n=0, m=0;  
n = m++; /*first assign m's value to n, then increment m*/  
cout << n << m; /*display 0 1*/

In this example, n equals 0 after the assignment because the increment operation took place after m's original value was taken and assigned to n.
To understand the difference between postfix and prefix operators better, examine the disassembly code generated for these operations. Even if you're not familiar with assembly languages, you can immediately see the difference between the two; simply notice where the inc (increment) assembly directive appears:

Code:

/*disassembly of the expression: m=n++;*/  
mov ecx, [ebp-0x04] /*store n's value in ecx register*/  
mov [ebp-0x08], ecx /*assign value in ecx to m*/  
inc dword ptr [ebp-0x04] /*increment n*/  
  
/*disassembly of the expression: m=++n;*/  
inc dword ptr [ebp-0x04] /*increment n;*/  
mov eax, [ebp-0x04] /*store n's value in eax register*/  
mov [ebp-0x08], eax /*assign value in eax to m*/

[shailu]

hi man in post fix first the condition check then increment and in prefix first the increment than check the condition........

[Abitha]

In prefix, first the value is incremented and then the value is assigned.
In postfix, first the value is assigned and then incremented

[Ken Peterson]

It is important to note that a postfix increment or decrement expression evaluates to the value of the expression prior to application of the respective operator. The increment or decrement operation occurs after the operand is evaluated. This issue arises only when the postfix increment or decrement operation occurs in the context of a larger expression.