The cell phone modem is a separate hardware piece in your phone, it has its own operating system. The smartphone OS communicates with the modem over an interface usually using "AT" commands. The iPhone 1-4 had an cell phone modem design by Intel (GSM version, modem manufacturer got bought by Intel).
The iOS UI consists app(s), so it may crash and restart.
The cell phone modem is a separate hardware piece in your phone, it has its own operating system. The smartphone OS communicates with the modem over an interface usually using "AT" commands. The iPhone 1-4 had an cell phone modem design by Intel (GSM version, modem manufacturer got bought by Intel).
The iOS UI consists app(s), so it may crash and restart.