page_title: BIOS
hierarchical_section_title: BIOS
caption_attribution_description: English: A pair of American Megatrends Inc. (AMI) BIOS chips from a Dell 310, a late-1980s computer based on the Intel 80386.
context_page_description: BIOS is firmware used to perform hardware initialization during the booting process, and to provide runtime services for operating systems and programs. The BIOS firmware comes pre-installed on a personal computer's system board, and it is the first software to run when powered on. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by companies looking to create compatible systems. The interface of that original system serves as a de facto standard.
  The BIOS in modern PCs initializes and tests the system hardware components, and loads a boot loader from a mass memory device which then initializes an operating system. In the era of DOS, the BIOS provided a hardware abstraction layer for the keyboard, display, and other input/output devices that standardized an interface to application programs and the operating system. More recent operating systems do not use the BIOS after loading, instead accessing the hardware components directly.
context_section_description: BIOS (pronounced: /ˈbaɪɒs/, BY-oss; an acronym for Basic Input/Output System and also known as the System BIOS, ROM BIOS or PC BIOS) is firmware used to perform hardware initialization during the booting process (power-on startup), and to provide runtime services for operating systems and programs. The BIOS firmware comes pre-installed on a personal computer's system board, and it is the first software to run when powered on. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by companies looking to create compatible systems. The interface of that original system serves as a de facto standard.
  The BIOS in modern PCs initializes and tests the system hardware components, and loads a boot loader from a mass memory device which then initializes an operating system. In the era of DOS, the BIOS provided a hardware abstraction layer for the keyboard, display, and other input/output (I/O) devices that standardized an interface to application programs and the operating system. More recent operating systems do not use the BIOS after loading, instead accessing the hardware components directly.
  Most BIOS implementations are specifically designed to work with a particular computer or motherboard model, by interfacing with various devices that make up the complementary system chipset. Originally, BIOS firmware was stored in a ROM chip on the PC motherboard. In modern computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard.  This allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it also creates a possibility for the computer to become infected with BIOS rootkits. Furthermore, a BIOS upgrade that fails can brick the motherboard permanently, unless the system includes some form of backup for this case.
  Unified Extensible Firmware Interface (UEFI) is a successor to the legacy PC BIOS, aiming to address its technical limitations.
caption: A pair of AMD BIOS chips for a Dell 310 computer from the late 1980s
exif: {"Image Make": "NIKON CORPORATION", "Image Model": "NIKON D7100", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "DxO OpticsPro 11.4.2", "Image DateTime": "2018:01:31 16:39:06", "Image Artist": "Judson McCranie, jud@judmccranie.com", "Image Copyright": "Copyright Jud McCranie 2017", "Image ExifOffset": "364", "GPS GPSVersionID": "[2, 3, 0, 0]", "Image GPSInfo": "23658", "Image DateTimeOriginal": "2018:01:31 16:39:06", "Image Tag 0x9216": "[1, 0, 0, 0]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "23790", "Thumbnail JPEGInterchangeFormatLength": "15239", "EXIF ExposureTime": "1/80", "EXIF FNumber": "22", "EXIF ExposureProgram": "Aperture Priority", "EXIF ISOSpeedRatings": "3200", "EXIF SensitivityType": "Recommended Exposure Index", "EXIF DateTimeOriginal": "2018:01:31 16:39:06", "EXIF DateTimeDigitized": "2018:01:31 16:39:06", "EXIF ShutterSpeedValue": "790241/125000", "EXIF ApertureValue": "445943/50000", "EXIF ExposureBiasValue": "1/3", "EXIF MaxApertureValue": "7/2", "EXIF SubjectDistance": "1/5", "EXIF MeteringMode": "CenterWeightedAverage", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "40", "EXIF SubSecTime": "40", "EXIF SubSecTimeOriginal": "40", "EXIF SubSecTimeDigitized": "40", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "4511", "EXIF ExifImageLength": "4000", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CVAPattern": "[2, 0, 2, 0, 0, 1, 1, 2]", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF FocalLengthIn35mmFilm": "60", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "High gain up", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}