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[edit section] How An Operating System Works With Hardware & Software

[edit section] Quick Fact Sheet

• Ports on the motherboard include serial, parallel, USB, mouse, keyboard, FireWire ports.

• The motherboard is the largest circuit board inside the computer case and holds the CPU, the most important microchip inside a computer, which is responsible for all processing done by the system.

• A CPU can operate in real or protected mode. In real mode, it processes 16 bits at a time, and in protected mode, it process 32 bits at a time.

• Real mode runs a single program using a 16-bit data path and protected mode can multitask using a 32-bit data path.

• RAM (memory) temporarily holds data and programs while the CPU processes both. Common RAM modules installed on the motherboard is SIMMs, DIMMs, and RIMMs.

• A motherboard has several buses, each designed for a different purpose and turning at a different speed. Some buses are the 8-bit and 16-bit ISA buses, the system bus, the PCI bus, the AGP bus used for a single video card, the USB bus that provides USB ports for slower I/O devices, and IEEE 1394 (FireWire) used for faster I/O devices.

• BIOS and an OS can support these common standards, ACPI and APM to conserve power, and Plug and Play to make device installations easier.

• BIOS manages a CMOS RAM chip on the motherboard that contains configuration settings for the motherboard. A program in BIOS lets you change CMOS setup at startup.

• Most hard drives and other secondary storage devices use IDE technology, which can support up to 4 drives in a system. There are two IDE connections on the motherboard, for two cables. Each cable can connect two drives.

• A file system is a method by which the OS organizes the files on a hard drive. The most popular file system for Windows is FAT, which can be either FAT16 or FAT32.

• Using FAT, clusters are listed in the FAT and filenames are listed in a directory table.

• Directories (folders) can contain files and other child directories or subdirectories (folders)

• Application software relates to the OS, which relates to BIOS and device drivers to control hardware.

• From the Windows Desktop, programs can be launched from the Start menu, a shortcut icon on the desktop, the Run dialog box, Windows Explorer, or My Computer.

• Most PC software falls into three categories: Device drivers or the BIOS, operating system, and application software.

• Device drivers are complied as either 16-bit or 32-bit software. Most drivers today are 32-bit protected-mode drivers that Windows loads from the registry.

• Windows 95/98 loads older 16-bit device drivers fro from Autoexec.bat, Config.sys, or System.ini to backward compatible with DOS and Windows 3.x.

• 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 needing service uses to alert the CPU.

• The CPU places a device’s I/O address on the address bus when it wants to initiate communication with the device.

• Memory addresses are numbers assigned to physical memory (RAM) that software use to access this memory.

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

• Three Windows utilities useful for gathering information about a system are Device Manager, System Information, and Microsoft Dianostic Utility (MSD).

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