# C If ... Else

## Conditions and If Statements

You have already learned that C supports the usual logical conditions from mathematics:

• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b
• Equal to a == b
• Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

C has the following conditional statements:

• Use `if` to specify a block of code to be executed, if a specified condition is `true`
• Use `else` to specify a block of code to be executed, if the same condition is `false`
• Use `else if` to specify a new condition to test, if the first condition is `false`
• Use `switch` to specify many alternative blocks of code to be executed

## The if Statement

Use the `if` statement to specify a block of code to be executed if a condition is `true`.

### Syntax

if (condition) {
// block of code to be executed if the condition is true
}

Note that `if` is in lowercase letters. Uppercase letters (If or IF) will generate an error.

In the example below, we test two values to find out if 20 is greater than 18. If the condition is `true`, print some text:

### Example

if (20 > 18) {
printf("20 is greater than 18");
}
Try it Yourself »

We can also test variables:

### Example

int x = 20;
int y = 18;
if (x > y) {
printf("x is greater than y");
}
Try it Yourself »

#### Example explained

In the example above we use two variables, x and y, to test whether x is greater than y (using the `>` operator). As x is 20, and y is 18, and we know that 20 is greater than 18, we print to the screen that "x is greater than y".

## The else Statement

Use the `else` statement to specify a block of code to be executed if the condition is `false`.

### Syntax

if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}

### Example

int time = 20;
if (time < 18) {
printf("Good day.");
} else {
printf("Good evening.");
}
// Outputs "Good evening."
Try it Yourself »

#### Example explained

In the example above, time (20) is greater than 18, so the condition is `false`. Because of this, we move on to the `else` condition and print to the screen "Good evening". If the time was less than 18, the program would print "Good day".

## The else if Statement

Use the `else if` statement to specify a new condition if the first condition is `false`.

### Syntax

if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}

### Example

int time = 22;
if (time < 10) {
printf("Good morning.");
} else if (time < 20) {
printf("Good day.");
} else {
printf("Good evening.");
}
// Outputs "Good evening."
Try it Yourself »

#### Example explained

In the example above, time (22) is greater than 10, so the first condition is `false`. The next condition, in the `else if` statement, is also `false`, so we move on to the `else` condition since condition1 and condition2 is both `false` - and print to the screen "Good evening".

However, if the time was 14, our program would print "Good day."

## Another Example

This example shows how you can use `if..else` to find out if a number is positive or negative:

### Example

int myNum = 10; // Is this a positive or negative number?

if (myNum > 0) {
printf("The value is a positive number.");
} else if (myNum < 0) {
printf("The value is a negative number.");
} else {
printf("The value is 0.");
}
Try it Yourself »

## Exercise:

Print "Hello World" if `x` is greater than `y`.

```int x = 50;
int y = 10;
(x  y) {
printf("Hello World");
}
```

Start the Exercise