#define is a useful C component that allows the programmer to give a name to a constant value before the program is compiled. Defined constants in arduino don't take up any program memory space on the chip. The compiler will replace references to these constants with the defined value at compile time.

This can have some unwanted side effects though, if for example, a constant name that had been #defined is included in some other constant or variable name. In that case the text would be replaced by the #defined number (or text).

In general, the const keyword is preferred for defining constants and should be used instead of #define.

This can have some unwanted side effects though, if for example, a constant name that had been #defined was included in some other constant or variable name.

In general the const is preferred for defining constants and should be used instead of #define.

• const

Similarly, including an equal sign after the #define statement will also generate a cryptic compiler error further down the page.

#define ledPin 3;    // this is an error 

#define ledPin  = 3  // this is also an error 

#define ledPin 3; // this is an error

#define ledPin = 3 // this is also an error

// The compiler will replace any mention of ledPin with the value 3 at compile time.@]

#define ledPin 3; // this is an error

Similarly including an equal sign after the #define statement will also generate a cryptic compiler error further down the page.

#define ledPin = 3 // this is also an error

See

There is no semicolon after the #define statement. If you include one, the compiler will throw cryptic errors further down the page.

#define is a useful C component that allows you to give a name to a constant value before the program is compiled.

=#=define is a useful C component that allows you to give a name to a constant value before the program is compiled.

Define

1. define is a useful C component that allows you to give a name to a constant value before the program is compiled.

See

• Constants

define is a useful C component that allows you to give a name to a constant value before the program is compiled. Defined constants in arduino don't take up any program memory space on the chip. The compiler will replace references to these constants with the defined value at compile time.

#define ledPin 3
//The compiler will replace any mention of ledPin with the value 3 at compile time.

Define

Defined constants in arduino don't take up any program memory space on the chip. The compiler will just replace references to these constants with the defined value at compile time.

Syntax

#define constantName value

Note that the # is necessary.

Example

#define ledPin 3

1. define is a useful C component that allows you to give a name to a constant value before the program is compiled.

You can define numbers in arduino that don't take up any program memory space on the chip.

Arduino defines have the same syntax as C defines:

Tip

The compiler will replace any mention of ledPin with the value 3 at compile time.

Common Programming Errors

There is no semicolon after the #define statement and the compiler will throw cryptic errors further down the page if you include one.

Defines

The compiler will replace any mentions of ledPin with the value 3 at compile time.

Reference Home

Defines

A define a useful C component that allow you to give a name to a value before the program is compiled.

You can define numbers in arduino that don't take up any program memory space on the chip. Arduino defines have the same syntax as C defines:

#define constantName value

Note that the # is necessary. For example:

#define ledPin 3

The compiler will replace any mentions of ledPin with the value 3 at compile time.