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==A block of code in if statement==

<source lang="cpp">#include <iostream>
using namespace std;

int main() {
double result, n, d;

cout << "Enter value: ";
cin >> n;

cout << "Enter divisor: ";
cin >> d;

if(d != 0) {
cout << "d does not equal zero so division is OK" << "\n";
result = n / d;
cout << n << " / " << d << " is " << result;
}

return 0;
}</source>
<pre class=codeResult>Enter value: 12
Enter divisor: 21
d does not equal zero so division is OK
12 / 21 is 0.571429"</pre>

==A nested if tatement==

<source lang="cpp">#include <iostream>

int main()
{
int firstNumber =2;
int secondNumber = 3;

if (firstNumber >= secondNumber)
{
if ( (firstNumber secondNumber) == 0) // evenly divisible?
{
if (firstNumber == secondNumber)
std::cout << "They are the same!\n";
else
std::cout << "They are evenly divisible!\n";
}
else
std::cout << "They are not evenly divisible!\n";
}
else
std::cout << "Hey! The second one is larger!\n";
return 0;
}</source>
<pre class=codeResult>Hey! The second one is larger!</pre>

==An if-else-if ladder.==

<source lang="cpp">#include <iostream>
using namespace std;

int main()
{
int x;

for(x=0; x<6; x++) {
if(x==1) cout << "x is one\n";
else if(x==2) cout << "x is two\n";
else if(x==3) cout << "x is three\n";
else if(x==4) cout << "x is four\n";
else cout << "x is not between 1 and 4\n";
}

return 0;
}</source>
<pre class=codeResult>x is not between 1 and 4
x is one
x is two
x is three
x is four
x is not between 1 and 4</pre>

==If else statement with block code==

<source lang="cpp">#include <iostream>
#include <cstdlib>

using namespace std;

int main()
{
int magic; // magic number
int guess; // user"s guess

magic = rand(); // get a random number

cout << "Enter your guess: ";
cin >> guess;

if (guess == magic) {
cout << "Right\n";
cout << magic << " is the magic number.\n";
}
else {
cout << "...Sorry, you"re wrong.";
if(guess > magic)
cout <<" Your guess is too high.\n";
else
cout << " Your guess is too low.\n";
}

return 0;
}</source>
<pre class=codeResult>Enter your guess: 3
...Sorry, you"re wrong. Your guess is too low.</pre>

==If statement with else==

<source lang="cpp">#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
int magic; // magic number
int guess; // user"s guess

magic = rand(); // get a random number

cout << "Enter your guess: ";
cin >> guess;

if(guess == magic)
cout << "Right";
else
cout << "...Sorry, you"re wrong.";

return 0;
}</source>
<pre class=codeResult>Enter your guess: 3
...Sorry, you"re wrong."</pre>

==if statement with variable logic operators==

<source lang="cpp">#include <iostream>
using namespace std;

int main() {
int a, b, c;

a = 2;
b = 3;

if(a < b)
cout << "a is less than b\n";

if(a == b)
cout << "you won"t see this\n";

cout << "\n";

c = a - b;

cout << "c contains -1\n";
if(c >= 0)
cout << "c is non-negative\n";
if(c < 0)
cout << "c is negative\n";

cout << "\n";

c = b - a; // c now contains 1
cout << "c contains 1\n";
if(c >= 0)
cout << "c is non-negative\n";
if(c < 0)
cout << "c is negative\n";

return 0;
}</source>
<pre class=codeResult>a is less than b
c contains -1
c is negative
c contains 1
c is non-negative</pre>

==if with else==

<source lang="cpp">#include <iostream>

int main()
{
int firstNumber, secondNumber;
std::cout << "Please enter a big number: ";
std::cin >> firstNumber;
std::cout << "\nPlease enter a smaller number: ";
std::cin >> secondNumber;
if (firstNumber > secondNumber)
std::cout << "\nThanks!\n";
else
std::cout << "\nOops. The second is bigger!";
return 0;
}</source>
<pre class=codeResult>Please enter a big number: 123
Please enter a smaller number: 12
Thanks!</pre>

==Proper use of braces with an if statement==

<source lang="cpp">#include <iostream>

int main()
{
int x = 12;

if (x > 10)
{
if (x > 100)
std::cout << "More than 100, Thanks!\n";
}
else // now works as intended!
std::cout << "Less than 10, Thanks!\n";
return 0;
}</source>

==Use an int value to control the if==

<source lang="cpp">#include <iostream>
using namespace std;

int main()
{
int a, b;

cout << "Enter numerator: ";
cin >> a;
cout << "Enter denominator: ";
cin >> b;

if(b)
cout << "Result: " << a / b << "\n";
else
cout << "Cannot divide by zero.\n";

return 0;
}</source>
<pre class=codeResult>Enter numerator: 2
Enter denominator: 4
Result: 0</pre>

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