title: Difference between "My Mac 32-bit" and "My Mac 64-bit" in Xcode 4?
body: <p>I have a Cocoa project that I recently imported into Xcode 4. I notice two Schemes for each of my specific build targets, one for 32-bit, and one for 64-bit. My Project settings are set to "Standard (32/64-bit Intel)".</p>
  
  <p>When I select the "My Mac 32-bit" Scheme, does this compile it for 32-bit machines, and selecting "My Mac 64-bit", then compiles it for 64-bit machines? If I select the "My Mac 64-bit" Scheme, will it no longer run on 32-bit machines at all?</p>
  
  <p><img src="https://i.stack.imgur.com/tH6tg.png" alt="enter image description here"></p>