The operating system has nothing to do with the ROM chip
A ROM chip
There are only two types: software and firmware. A software device driver is a program written for a particular operating system to support a particular piece of hardware. A firmware device driver is also software, but it is etched onto a memory chip (ROM) or a programmable chip (PROM or EPROM). The BIOS and CMOS are examples of firmware drivers, both used to initially boot the system and load the operating system.
An operating system is like Windows, Windows 2000, Windows XP, it's the controlling software of your computer. A microprocessor is the CPU, the brain of the computer. It does all the commands, does all the math, and displays the answers on you monitor. So the CPU is called hardware because it is an actual chip, while the operating system is called software because it is millions of lines of computer code.
ROM
PLATFORM
utility program
Read only memory basic international operating system
It isn't. the operating system is installed in your Hard Drive...your BIOS are in your CMOS(a little chip on your motherboard) the two have nothing to do with each other
When replacing a BIOS chip, it is normal for the computer to display an error saying that it cannot find the operating system. To fix this, simply change the boot order, putting the drive with the operating system as the first priority.
The CPU is the main logic chip or "brains" in the system. It is what runs all of your software, and it is required for the computer to do anything at all. It is the "brains" regardless of whether an operating system or other software is installed. Even without the OS, you have the BIOS, EFI, or other firmware that gives it the ability to configure core system hardware and the ability to load an operating system.
Obviously many different PDAs have different names for their operating systems. But generally you would call it an embedded operating system, as it is running on an embedded device.
It is typically burned into a tiny ROM chip on the phone's circuit board.