How Software and Hardware Work Together

·         Four system resources that aid in the communication between hardware and software are I/O addresses, IRQs, DMA channels and memory addresses.

·         An IRQ is a line on a bus that a device uses to alert the CPU that it needs servicing.

·         A DMA channel provides a shortcut for a device to send data directly to memory, bypassing the CPU.

·         Memory addresses are hex numbers, often written in segment/offset form, assigned to RAM and ROM so that the CPU can access both.

·         The CPU sends a device’s I/O address over the address bus when it wants to initiate communication with the device.

·         Startup BIOS performs a power-on self test (POST) that surveys and tests hardware, examines setup information, and assigns system resources to the hardware.  Startup BIOS then begins the process of loading the OS.

·         When the OS loads from a hard drive, the first program BIOS executes is the master boot record (MBR), which executes the OS boot record, which, for DOS, attempts to find IO.SYS and MSDOS.SYS on the hard drive.

·         IO.SYS and MSDOS.SYS together with COMMAND.COM form the kernel or core, of DOS.

·         AUTOEXEC.BAT and CONFIG.SYS are two files that contain commands used to customize the OS load process.

·         After DOS is loaded, Windows 3.x can be executed from the WIN command stored in AUTOEXEC.BAT.

·         Windows 9x uses Plug and Play to help install devices and assign resources to them during the boot process.

·         In Windows 9x, the file MSDOS.SYS is a text file that contains parameters to customize the boot.

·         One bus used on early PCs is the 8-bit ISA bus, which was later improved to become the 16-bit ISA bus that is still used on PCs today.

·         Under Windows 9x, use Device Manager to find out how system resources have been allocated in your system.

·         A hardware interrupt is initiated by a hardware device sending and IRQ to the CPU.  A software interrupt is initiated by the software sending and interrupt number (INT) to the CPU.

·         Setup data can be stored on the CMOS chip on the system board and by DIP switches or jumpers.

·         There are several utility programs, such as Nuts & Bolts and Norton Utilities, that can save a copy of CMOS setup to disk.  Use these to back up setup information.

·         For safety’s sake, back up important information on your hard drive, keep documentation in a safe place, and protect your computer against both static electricity and electrical power surges.