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Saturday, 7 March 2015

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Laptop Biography

Source:- Google.com.pk
The BIOS (/ˈbaɪ.ɒs/, an acronym for Basic Input/Output System and also known as the System BIOS, ROM BIOS or PC BIOS) is a type of firmware used during the bootingprocess (power-on startup) on IBM PC compatible computers.[1] The BIOS firmware is built into PCs, and it is the first software they run when powered on. The name itself originates from the Basic Input/Output System used in the CP/M operating system in 1975.[2][3] Originally proprietary to the IBM PC, the BIOS was reverse engineered by companies looking to create compatible systems and the interface of that original system serves as a de facto standard.
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. MSWindows 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.
Every BIOS implementation is 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 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.
Unified Extensible Firmware Interface (UEFI) was designed as a successor to BIOS, aiming to address its technical shortcomings.[4] As of 2014, new PC hardware predominantly ships with UEFI firmware.With the introduction of PS/2 machines, IBM divided the System BIOS into real-mode and protected mode portions. The real-mode portion was meant to provide backward-compatibility with existing operating systems such as DOS, and therefore was named "CBIOS" (for Compatibility BIOS), whereas the "ABIOS" (for Advanced BIOS) provided new interfaces specifically suited for multitasking operating systems such as OS/2.The BIOS of the original IBM PC XT had no interactive user interface. Error codes or messages were displayed on the screen, or coded series of sounds were generated to signal errors (when the POST had not proceeded to the point of successfully initializing a video display adapter). Options on the PC and XT were set by switches and jumpers on the main board and on peripheral cards. Starting around the mid-1990s, it became typical for the BIOS ROM to include a "BIOS configuration utility" (BCU[8]) or "BIOS setup utility", accessed at system power-up by a particular key sequence. This program allowed the user to set system configuration options, of the type formerly set using DIP switches, through an interactive menu system controlled through the keyboard. In the interim period, IBM-compatible PCs—including the IBM AT—held configuration settings in battery-backed RAM and used a bootable configuration program on disk, not in the ROM, to set the configuration options contained in this memory. The disk was supplied with the computer, and if it was lost the system settings could not be changed.
A modern Wintel-compatible computer provides a setup routine essentially unchanged in nature from the ROM-resident BIOS setup utilities of the late 1990s; the user can configure hardware options using the keyboard and video display. Also, when errors occur at boot time, a modern BIOS usually displays user-friendly error messages, often presented as pop-up boxes in a TUI style, and offers to enter the BIOS setup utility or to ignore the error and proceed if possible. Instead of battery-backed RAM, the modern Wintel machine may store the BIOS configuration settings in flash ROM, perhaps the same flash ROM that holds the BIOS itself.

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