Virtually all industrial PCs share an underlying design philosophy of providing a controlled environment for the installed electronics to survive the rigors of the plant floor. The electronic components themselves may be selected for their ability to withstand higher and lower operating temperatures than typical commercial components.
Heavier metal construction as compared to the typical office non-rugged computer
Enclosure form factor that includes provision for mounting into the surrounding environment (19" rack, wall mount, panel mount, etc.)
Additional cooling with air filtering
Alternative cooling methods such as forced air, liquid, and conduction
Expansion card retention and support
Enhanced EMI filtering and gasketing
Enhanced environmental protection such as dust proof, water spray or immersion proof, etc.
Sealed MIL-SPEC or Circular-MIL connectors
More robust controls and features
Higher grade power supply
Controlled access to the controls through the use of locking doors
Controlled access to the I/O through the use of access covers
Inclusion of a watchdog timer to reset the system automatically in case of software lock-up