user2955: I'm trying to program AtTiny13 using Arduino IDE. I have connected the atTiny to my PC using USBasp programer.
I want to write a simple blink application to test whether it works or not. Which pins should I blink?

user973: You'll need an Arduino library that supports that chip, to make it appear in the Tools > Board list.  The library docs will tell you which pins then correspond to which Arduino digital I/Os. From that you can decide which pin to attach an LED to (with resistor) and how to edit the blink sketch.
Example: http://www.instructables.com/id/Pimp-Your-Chocolates-with-Arduino-IDE-and-ATtiny13/step2/Program-the-ATtiny13/

user4951: Because pins 0 and 1 (physical 5,6) are PWM's you should keep them for later ...
and you still have A3 and A2 for analogWrite so,
you should use Pin 2 (Physical 7, next to +5V) like this : 
add this in the setup function
pinMode(2, OUTPUT);

And add this in your loop function:
digitalWrite(2,HIGH);


For reference : 
SparkFun's Help guide
Remember : Physical pin "1", reset, has a dot  marked on it. 

2955: <p>I'm trying to program AtTiny13 using Arduino IDE. I have connected the atTiny to my PC using USBasp programer.</p>

<p>I want to write a simple blink application to test whether it works or not. Which pins should I blink?</p>
 973: <p>You'll need an Arduino library that supports that chip, to make it appear in the Tools > Board list.  The library docs will tell you which pins then correspond to which Arduino digital I/Os. From that you can decide which pin to attach an LED to (with resistor) and how to edit the blink sketch.</p>

<p>Example: <a href="http://www.instructables.com/id/Pimp-Your-Chocolates-with-Arduino-IDE-and-ATtiny13/step2/Program-the-ATtiny13/" rel="nofollow">http://www.instructables.com/id/Pimp-Your-Chocolates-with-Arduino-IDE-and-ATtiny13/step2/Program-the-ATtiny13/</a></p>
 4951: <p>Because pins 0 and 1 (physical 5,6) are PWM's you should keep them for later ...
and you still have A3 and A2 for analogWrite so,
you should use Pin 2 (Physical 7, next to +5V) like this : </p>

<p>add this in the setup function</p>

<pre><code>pinMode(2, OUTPUT);
</code></pre>

<p>And add this in your loop function:</p>

<pre><code>digitalWrite(2,HIGH);
</code></pre>

<p><img src="https://i.stack.imgur.com/GwRJ9.png" alt="In case you forget"></p>

<p>For reference : 
<a href="https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/attiny85-use-hints" rel="nofollow noreferrer">SparkFun's Help guide</a></p>

<p>Remember : Physical pin "1", reset, has a dot  marked on it. </p>
