user25987: we have an error after compiling the code in arduinouno that is displayed as
error: 'power_usi_disable' was not declared in this scope   in Board: "Arduino/Genuino Uno".how to rectify this error. please reply us fast

user7508: The Arduino Uno does not have a USI peripheral. Thus, you cannot disable
the power of the (non-existent) USI, and there is no
power_usi_disable() function.
Solution: remove the call to power_usi_disable() from your code.
Update: To answer your new question in the comment, WDTCR is the
Watchdog Timer Control Register on some AVR chips. On the Uno it is
called WDTCSR, because it is a control and status register.
Looks to me like you have downloaded from somewhere a program you do not
understand. That program was written for an ATtiny chip and you are
trying to compile it as-is for an Arduino Uno, which is based on an
(incompatible) ATmega328P. That's not the way to do it: you have to
understand the program and rewrite all the ATtiny specific stuff to fit
the Uno.

25987: <p>we have an error after compiling the code in arduinouno that is displayed as<br>
error: 'power_usi_disable' was not declared in this scope   in Board: "Arduino/Genuino Uno".how to rectify this error. please reply us fast</p>
 7508: <p>The Arduino Uno does not have a USI peripheral. Thus, you cannot disable
the power of the (non-existent) USI, and there is no
<code>power_usi_disable()</code> function.</p>

<p>Solution: remove the call to <code>power_usi_disable()</code> from your code.</p>

<p><strong>Update</strong>: To answer your <em>new</em> question in the comment, <code>WDTCR</code> is the
Watchdog Timer Control Register on some AVR chips. On the Uno it is
called <code>WDTCSR</code>, because it is a control and status register.</p>

<p>Looks to me like you have downloaded from somewhere a program you do not
understand. That program was written for an ATtiny chip and you are
trying to compile it as-is for an Arduino Uno, which is based on an
(incompatible) ATmega328P. That's not the way to do it: you have to
understand the program and rewrite all the ATtiny specific stuff to fit
the Uno.</p>
