Dev c++ 3rd class

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Solved  By : Tahir Siddiqui(Mani)

BC-140201235@Vu.edu.pk

Dev c++ 3rd  lecture :

Today Topic :Increment/decrements operators, and side effects :

Incrementing (adding 1 to) and decrementing (subtracting 1 from) a variable are so common that they have their own operators in C. There are actually two versions of each operator -- a prefix version and a postfix version.

Operator	Symbol	Form	Operation
Prefix increment (pre-increment)	++	++x	Increment x, then evaluate x
Prefix decrement (pre-decrement)	––	––x	Decrement x, then evaluate x
Postfix increment (post-increment)	++	x++	Evaluate x, then increment x
Postfix decrement (post-decrement)	––	x––	Evaluate x, then decrement x

for Example :

int x = 5;

int y = ++x;    // x is now equal to 6, and 6 is assigned to y

int x = 5;

int y = x++;       // x is now equal to 6, and 5 is assigned to y

Here is another example showing the difference between the prefix and postfix versions:

int x = 5, y = 5;

cout << x << " " << y << endl;

cout << ++x << " " << --y << endl; // prefix

cout << x << " " << y << endl;

cout << x++ << " " << y-- << endl; // postfix

cout << x << " " << y << endl;

This produces the output:

5 5
6 4
6 4
6 4
7 3

Relational operators (comparisons)

There are 6 relational operators:

Operator	Symbol	Form	Operation
Greater than	>	x > y	true if x is greater than y, false otherwise
Less than	<	x < y	true if x is less than y, false otherwise
Greater than or equals	>=	x >= y	true if x is greater than or equal to y, false otherwise
Less than or equals	<=	x <= y	true if x is less than or equal to y, false otherwise
Equality	==	x == y	true if x equals y, false otherwise
Inequality	!=	x != y	true if x does not equal y, false otherwise

You have already seen how all of these work, and they are pretty intuitive. Each of these operators evaluates to the boolean value true (1), or false (0).
Here’s some sample code using these operators with integers:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

#include <iostream> int main() {     std::cout << "Enter an integer: ";     int x;     std::cin >> x;     std::cout << "Enter another integer: ";     int y;     std::cin >> y;     if (x == y)         std::cout << x << " equals " << y << "\n";     if (x != y)         std::cout << x << " does not equal " << y << "\n";     if (x > y)         std::cout << x << " is greater than " << y << "\n";     if (x < y)         std::cout << x << " is less than " << y << "\n";     if (x >= y)         std::cout << x << " is greater than or equal to " << y << "\n";     if (x <= y)         std::cout << x << " is less than or equal to " << y << "\n";     return 0; }

And the results from a sample run:

Enter an integer: 4 Enter another integer: 5 4 does not equal 5 4 is less than 5 4 is less than or equal to 5 These operators are extremely straightforward to use when comparing integers.