What is the BIOS? What's the effect?

What is the BIOS? The first part is used to detect the hardware part of the computer when it is just plugged in, also known as the Power-on self-test (Power On Self test, short post), which checks the computer for good, usually full post self-test will include the basic memory for cpu,640k, More than 1M of extended memory, ROM, motherboard, CMOS memory, serial port, display card, soft hard plate system and keyboard for testing, BIOS features once in the self-test found problems, the system will give a message or siren warning. If an error is found in the self-test, will be handled in two cases: for a serious failure (fatal failure) is down, at this time due to a variety of initialization operations are not completed, can not give any hint or signal; For non serious failure, give a hint or sound alarm signal, waiting for the user to process.

The second part of the BIOS feature is initialized, this includes creating interrupt vectors, setting registers, initializing and detecting some external devices, and a very important part of the BIOS settings, mainly the parameters that are set on the hardware, which are read when the computer is started and compared to the actual hardware settings. If not, what the BIOS will affect the boot of the system.

The third part of the BIOS feature is the boot program, which is what the BIOS is capable of booting DOS or other operating systems. The BIOS first reads the boot record from the start sector of the floppy disk or hard disk. If not found, the display will be displayed without a boot device, if the boot record is found will transfer control of the computer to the boot record, the boot record of the operating system into the computer, after the computer started successfully, the BIOS this part of the task is completed.

　　BIOS feature Program Service processing

What is the BIOS? The program service handlers are primarily for applications and operating systems, and these services are primarily related to input, such as read disks, file output to printers, and so on. To do this, the BIOS must deal directly with the computer's I/O device, which sends commands through the port, transmits data to various external devices, and receives data from them, allowing the program to disengage from specific hardware operations.

　　BIOS feature hardware interrupt handling

Hardware interrupt processing is handled separately for PC hardware requirements, and the BIOS service function is implemented by invoking the Interrupt service program, which is divided into many groups with a dedicated interrupt per group. For example, video service, interrupt number 10H, screen printing, interrupt number 05H, disk and serial port service, interrupt 14H, etc. What is the BIOS? Each group is subdivided into different service numbers according to the specific function. Which peripherals the application needs to use, and what to do, requires instructions in the program, without direct control.