Pre-increment and Post-increment in C/C++

Pre-increment operator: A pre-increment operator is used to increment the value of a variable before using it in a expression. In the Pre-Increment, value is first incremented and then used inside the expression.

Syntax:

 a = ++x;

Here, if the value of ‘x’ is 10 then value of ‘a’ will be 11 because the value of ‘x’ gets modified before using it in the expression.

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// CPP program to demonstrate pre increment
// operator.
#include <iostream>
using namespace std;
  
int main()
{
    int x = 10, a;
  
    a = ++x;
    cout << "Pre Increment Operation";
  
    // Value of a will change
    cout << "\na = " << a;
  
    // Value of x change before execution of a=++x;
    cout << "\nx = " << x;
  
    return 0;
}

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Output :

Pre Increment Operation
a = 11
x = 11

Post-increment operator: A post-increment operator is used to increment the value of variable after executing expression completely in which post increment is used. In the Post-Increment, value is first used in a expression and then incremented.
Syntax:

 a = x++;

Here, suppose the value of ‘x’ is 10 then value of variable ‘b’ will be 10 because old value of ‘x’ is used.

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// CPP program to demonstrate pre increment
// operator.
#include <iostream>
using namespace std;
  
int main()
{
    int x = 10, a;
  
    a = x++;
  
    cout << "Post Increment Operation";
  
    // Value of a will not change
    cout << "\na = " << a;
  
    // Value of x change after execution of a=x++;
    cout << "\nx = " << x;
  
    return 0;
}

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Output :

Post Increment Operation
a = 10
x = 11

Evaluating post and pre-increment together

Precedence of postfix ++ is more than prefix ++ and their associativity is also different. Associativity of prefix ++ is right to left and associativity of postfix ++ is left to right.

    • Associativity of postfix ++ is left to right
    • Associativity of prefix ++ is right to left

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