Rugged handheld mobile computers typically have a larger form factor than PDA's and are designed for use in harsh environments.
Most have an IP rating (Ingress Protection) of 54 or above and thus can be used in environments where there is dust and water/rain.
Find out more about IP Ratings.
Many rugged handheld PCs combine input options, including keypad and bar-code readers and RFID is now becoming more common. Multiple radio communication options, such as WPAN (Bluetooth), WLAN (802.11b/g) and WWAN (GSM/GPRS) are also available.
Applications are normally written in Windows Mobile® and Win CE.Net™.
Rugged mobile computers tend to be more robust than PDAs and normally have many value added features (barcoding, smart card reading, imaging, RFID, GPS) and communication options (WPAN, WLAN, WWAN).