# Conditionals & Logic

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### `if` Statement

An `if` statement is used to test an expression for truth.

• If the condition evaluates to `true`, then the code within the block is executed; otherwise, it will be skipped.
``````if (a == 10) {
// Code goes here
}``````

### Relational Operators

Relational operators are used to compare two values and return `true` or `false` depending on the comparison:

• `==` equal to

• `!=` not equal to

• `>` greater than

• `<` less than

• `>=` greater than or equal to

• `<=` less than or equal to

``````if (a > 10) {
// ☝️ means greater than
}``````

### `else` Clause

An `else` clause can be added to an `if` statement.

• If the condition evaluates to `true`, code in the `if` part is executed.
• If the condition evaluates to `false`, code in the `else` part is executed.
``````if (year == 1991) {
// This runs if it is true
}
else {
// This runs if it is false
}``````

### `switch` Statement

A `switch` statement provides a means of checking an expression against various `case`s. If there is a match, the code within starts to execute. The `break` keyword can be used to terminate a case.

`default` is executed when no case matches.

``````switch (grade) {
case 9:
std::cout << "Freshman\n";
break;
case 10:
std::cout << "Sophomore\n";
break;
case 11:
std::cout << "Junior\n";
break;
case 12:
std::cout << "Senior\n";
break;
default:
std::cout << "Invalid\n";
break;
}``````

### `else if` Statement

One or more `else if` statements can be added in between the `if` and `else` to provide additional condition(s) to check.

``````if (apple > 8) {
// Some code here
}
else if (apple > 6) {
// Some code here
}
else {
// Some code here
}``````

### Logical Operators

Logical operators can be used to combine two different conditions.

• `&&` requires both to be true (`and`)
• `||` requires either to be true (`or`)
• `!` negates the result (`not`)
``````if (coffee > 0 && donut > 1) {
// Code runs if both are true
}

if (coffee > 0 || donut > 1) {
// Code runs if either is true
}

if (!tired) {
// Code runs if tired is false
}``````

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