Basic Input/Output System (BIOS, also known as System BIOS, ROM BIOS or PC BIOS (/ˈbaɪ.ɒs/)) is the de facto standard defining the interface for firmware on IBM PC compatible computers. The name originated from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS software is built into the PC, and it is the first software run by a PC when powered on.The fundamental purposes of the BIOS are to initialize and test the system hardware components, and to load a boot loader or an operating system from a mass memory device. The BIOS additionally provides an abstraction layer for the hardware, i.e. a consistent way for application programs and operating systems to interact with the keyboard, display, and other input/output devices. Variations in the system hardware are hidden by the BIOS from programs that use BIOS services instead of directly accessing the hardware. MS-DOS (PC DOS), which was the dominant PC operating system from the early 1980s until the mid 1990s, relied on BIOS services for disk, keyboard, and text display functions. MS Windows NT, Linux, and other protected mode operating systems in general ignore the abstraction layer provided by the BIOS and do not use it after loading, instead accessing the hardware components directly.BIOS software is stored on a ROM chip on the motherboard. It is specifically designed to work with each particular model of computer, interfacing with various devices that make up the complementary chipset of the system. In modern computer systems, the BIOS contents are stored on flash memory so that the contents can be rewritten without removing the chip from the motherboard. This allows BIOS software to be easily upgraded to add new features or fix bugs, but can make the computer vulnerable to BIOS rootkits.BIOS technology is in transitional process toward the Unified Extensible Firmware Interface (UEFI) since 2010.