# Compile Errors for Included Files

**URL:** <https://community.particle.io/t/compile-errors-for-included-files/19047>\
**Category:** Getting Started\
**Created:** [January 13, 2016, 7:11pm UTC](https://community.particle.io/t/compile-errors-for-included-files/19047 "2016-01-13T19:11:26Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![ilehrman](https://avatars.discourse-cdn.com/v4/letter/i/ecccb3/32.png) [@ilehrman](https://community.particle.io/u/ilehrman)\
**Post date:** [January 13, 2016, 7:11pm UTC](https://community.particle.io/t/compile-errors-for-included-files/19047/1 "2016-01-13T19:11:26Z")

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I am having problems compiling a file that contains Particle defined functions and variables. I copied a section of code that works perfectly fine in a code.ino file, but when I copy and paste the class definition in a .cpp file, I get the following errors:

LEDBlink.cpp: In constructor ‘LEDBlink::LEDBlink(int, unsigned int)’:  
LEDBlink.cpp:26:19: error: ‘OUTPUT’ was not declared in this scope  
pinMode(\_Pin, OUTPUT); //Define Pin as output  
^

LEDBlink.cpp:26:25: error: ‘pinMode’ was not declared in this scope  
pinMode(\_Pin, OUTPUT); //Define Pin as output  
^

LEDBlink.cpp:27:33: error: ‘digitalWrite’ was not declared in this scope  
digitalWrite(\_Pin, \_ledState); //LED off  
^

LEDBlink.cpp:28:20: error: ‘millis’ was not declared in this scope  
\_time = millis(); //set initial time  
^

LEDBlink.cpp: In member function ‘void LEDBlink::update()’:  
LEDBlink.cpp:36:16: error: ‘millis’ was not declared in this scope  
if((millis() - \_time) \> \_delay)  
^

LEDBlink.cpp:39:37: error: ‘digitalWrite’ was not declared in this scope  
digitalWrite(\_Pin, \_ledState); //Write LED State  
^

LEDBlink.cpp: In member function ‘void LEDBlink::on()’:  
LEDBlink.cpp:48:33: error: ‘digitalWrite’ was not declared in this scope  
digitalWrite(\_Pin, \_ledState);  
^

LEDBlink.cpp: In member function ‘void LEDBlink::off()’:  
LEDBlink.cpp:55:33: error: ‘digitalWrite’ was not declared in this scope  
digitalWrite(\_Pin, \_ledState);  
^

Any help is appreciated!

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<div class="post-metadata">

**Author:** ![peekay123](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/peekay123/32/810_2.png) [@peekay123](https://community.particle.io/u/peekay123)\
**Post date:** [January 13, 2016, 8:23pm UTC](https://community.particle.io/t/compile-errors-for-included-files/19047/2 "2016-01-13T20:23:22Z")

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@ilehrman, you are most likely missing an `#include "application.h"` at the top of your file! 😉

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<div class="post-metadata">

**Author:** ![ilehrman](https://avatars.discourse-cdn.com/v4/letter/i/ecccb3/32.png) [@ilehrman](https://community.particle.io/u/ilehrman)\
**Post date:** [January 13, 2016, 8:25pm UTC](https://community.particle.io/t/compile-errors-for-included-files/19047/3 "2016-01-13T20:25:34Z")

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Thank you! That worked. What functions are in the application.h file? I didn’t see any documentation on it in the particle docs.

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<div class="post-metadata">

**Author:** ![peekay123](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/peekay123/32/810_2.png) [@peekay123](https://community.particle.io/u/peekay123)\
**Post date:** [January 13, 2016, 8:29pm UTC](https://community.particle.io/t/compile-errors-for-included-files/19047/4 "2016-01-13T20:29:57Z")

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@ilehrman, `application.h` is like Arduino’s `arduino.h` which gets included in most `.h` or `.cpp` files. Wwhen using the web IDE with a .ino file, the IDE does that #include invisibly. For `.cpp` files, you need to add it explicitly. However, as you pointed out, it’s not really documented!

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<div class="post-metadata">

**Author:** ![ilehrman](https://avatars.discourse-cdn.com/v4/letter/i/ecccb3/32.png) [@ilehrman](https://community.particle.io/u/ilehrman)\
**Post date:** [January 13, 2016, 8:34pm UTC](https://community.particle.io/t/compile-errors-for-included-files/19047/5 "2016-01-13T20:34:03Z")

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Again, Thank you!