Ethernet.h error

Development Tools IDE 1.x
1

#include <Ethernet.h>
void setup() {
}
void loop() {
}

Ctrl+R

In file included from C:\Program Files (x86)\Arduino\libraries\Ethernet\src\Dhcp.cpp:4:0:
C:\Program Files (x86)\Arduino\libraries\Ethernet\src\utility/w5100.h:13:17: fatal error: SPI.h: No such file or directory
#include <SPI.h>
^
compilation terminated.

2

You need to "add" the SPI library.
The method depends on version of IDE.

3

If you look at the Ethernet examples they all start with:

#include <SPI.h>
#include <Ethernet.h>

You should do that, too.