It is often difficult for people to understand the difference between hardware and software in a PC system. The differences can be difficult because they are both very much intertwined in the system design, construction, and operation. Understanding these differences is essential to understanding the role of the BIOS in the system.
BIOS is a term that stands for basic input/output system , which at the most basic level consists of low-level software that controls the system hardware. BIOS is essentially the link between hardware and software in a system. Most people know the term BIOS by another name— device drivers, or just drivers . BIOS is a single term that describes all the drivers (low-level hardware control programs) in a system working together to act as an interface between the hardware and the operating system software.What can be confusing is that some of the BIOS code is burned or flashed into a ROM chip that is both nonvolatile (it doesn’t get erased when the power is turned off) and read-only. This is a core part of the BIOS, but not all of it. The BIOS also includes ROM chips installed on adapter cards, as well as all the additional drivers loaded when your system boots up. The combination of the motherboard BIOS, adapter card BIOS, and device drivers loaded from disk contribute to the BIOS as a whole. The portion of the BIOS contained in ROM chips both on the motherboard and in some adapter cards is sometimes called firmware , which is a name given to software stored in chips rather than on disk. This causes some people to incorrectly think of the BIOS as a hardware component. A PC system can be described as a series of layers—some hardware and some software—that interface with each other. In the most basic sense, you can break a PC down into four primary layers, each of which can be broken down further into subsets The purpose of the layered design is to enable a given operating system and applications to run on different hardware. different machines with different hardware can each use different drivers (BIOS) to interface the unique hardware to a common operating system and applications. Thus, two machines with different processors, storage media, video display units, and so on can run the same application software. In this layered architecture, the application software programs talk to the operating system via what is called an Application Program Interface (API). The API varies according to the operating system you are using and consists of the various commands and functions the operating system can perform for an application. For example, an application can call on the operating system to load or save a file. This prevents the application itself from having to know how to read the disk, send data to a printer,or perform any other of the many functions the operating system can provide. Because the application is completely insulated from the hardware, you can essentially run the same applications on different machines; the application is designed to talk to the operating system rather than the hardware. 
The operating system then interfaces with or talks to the BIOS or driver layer. The BIOS consists of all the individual driver programs that operate between the operating system and the actual hardware. Assuch, the operating system never talks to the hardware directly; instead, it must always go through the appropriate drivers. This provides a consistent way to talk to the hardware. It is usually the responsibility of the hardware manufacturer to provide drivers for its hardware. Because the drivers must act between both the hardware and the operating system, the drivers typically are operating system specific. Thus, the hardware manufacturer must offer different drivers so that its hardware works under DOS, Windows 9x, Windows NT, Windows 2000, OS/2, Linux, and so on. Because many operating systems use the same internal interfaces, some drivers can work under multiple operating systems. For example, a driver that works under Windows Me often also works under Windows 98 and 95, and a driver that works under Windows XP also often works under Windows 2000 and NT. 
This is because Windows 95, 98, and Me are essentially variations on the same OS, as are Windows NT, 2000,and XP.Because the BIOS layer looks the same to the operating system no matter what hardware is above it(or underneath, depending on your point of view), the same operating system can run on a variety of systems. For example, you can run Windows XP on two systems with different processors, hard disks, video adapters, and so on, yet Windows XP will look and feel pretty much the same on both of them.This is because the drivers provide the same basic functions no matter which specific hardware is used. 
BIOS is a term that stands for basic input/output system , which at the most basic level consists of low-level software that controls the system hardware. BIOS is essentially the link between hardware and software in a system. Most people know the term BIOS by another name— device drivers, or just drivers . BIOS is a single term that describes all the drivers (low-level hardware control programs) in a system working together to act as an interface between the hardware and the operating system software.What can be confusing is that some of the BIOS code is burned or flashed into a ROM chip that is both nonvolatile (it doesn’t get erased when the power is turned off) and read-only. This is a core part of the BIOS, but not all of it. The BIOS also includes ROM chips installed on adapter cards, as well as all the additional drivers loaded when your system boots up. The combination of the motherboard BIOS, adapter card BIOS, and device drivers loaded from disk contribute to the BIOS as a whole. The portion of the BIOS contained in ROM chips both on the motherboard and in some adapter cards is sometimes called firmware , which is a name given to software stored in chips rather than on disk. This causes some people to incorrectly think of the BIOS as a hardware component. A PC system can be described as a series of layers—some hardware and some software—that interface with each other. In the most basic sense, you can break a PC down into four primary layers, each of which can be broken down further into subsets The purpose of the layered design is to enable a given operating system and applications to run on different hardware. different machines with different hardware can each use different drivers (BIOS) to interface the unique hardware to a common operating system and applications. Thus, two machines with different processors, storage media, video display units, and so on can run the same application software. In this layered architecture, the application software programs talk to the operating system via what is called an Application Program Interface (API). The API varies according to the operating system you are using and consists of the various commands and functions the operating system can perform for an application. For example, an application can call on the operating system to load or save a file. This prevents the application itself from having to know how to read the disk, send data to a printer,or perform any other of the many functions the operating system can provide. Because the application is completely insulated from the hardware, you can essentially run the same applications on different machines; the application is designed to talk to the operating system rather than the hardware. 
The operating system then interfaces with or talks to the BIOS or driver layer. The BIOS consists of all the individual driver programs that operate between the operating system and the actual hardware. Assuch, the operating system never talks to the hardware directly; instead, it must always go through the appropriate drivers. This provides a consistent way to talk to the hardware. It is usually the responsibility of the hardware manufacturer to provide drivers for its hardware. Because the drivers must act between both the hardware and the operating system, the drivers typically are operating system specific. Thus, the hardware manufacturer must offer different drivers so that its hardware works under DOS, Windows 9x, Windows NT, Windows 2000, OS/2, Linux, and so on. Because many operating systems use the same internal interfaces, some drivers can work under multiple operating systems. For example, a driver that works under Windows Me often also works under Windows 98 and 95, and a driver that works under Windows XP also often works under Windows 2000 and NT. 
This is because Windows 95, 98, and Me are essentially variations on the same OS, as are Windows NT, 2000,and XP.Because the BIOS layer looks the same to the operating system no matter what hardware is above it(or underneath, depending on your point of view), the same operating system can run on a variety of systems. For example, you can run Windows XP on two systems with different processors, hard disks, video adapters, and so on, yet Windows XP will look and feel pretty much the same on both of them.This is because the drivers provide the same basic functions no matter which specific hardware is used. 
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