2 © 2004, Cisco Systems, Inc. All rights reserved. IT Essentials I v. 3 Module 4 Operating System Fundamentals.

2© 2004, Cisco Systems, Inc. All rights reserved.

IT Essentials I v. 3Module 4

Operating System Fundamentals

Module 4 Operating System Fundamentals

4.1 – The Operating System

4.2 – Disk Operating System (DOS)

4.3 – Memory Management

The Operating System

Components of an Operating System

• Operating Systems (OS) are software programs that control thousands of operations, provide an interface between the user and the computer, and run applications.

• An OS is designed to control the operations of programs such as web browsers, word processors, and e-mail programs.

Components of an Operating System

• Computers that handle concurrent users and multiple jobs are called "network servers" or "servers“.

• Servers have operating systems installed called Network Operating Systems (NOS).

• There are three basic elements that make up the major design components of any operating system.1. User interface

2. Kernel

3. File management system

Operating System Functions

• All operating systems perform the same basic functions:– File and folder management – Management of applications– Support for built-in utility programs– Access control to computer

hardware (The operating system can either access the hardware through the BIOS or through the device drivers Figure 2)

• Programs written for the UNIX operating system will not work on a Windows-based system, and vice versa.

Operating System Types - Basic Terminology

• The following terms are often used when comparing operating systems: – Multi-user – Multi-tasking– Multi-processing – Multi-threading

• A list of some of the most popular operating systems:– Microsoft Windows 95, 98, ME – Microsoft Windows NT/2000/XP– The Macintosh OS – UNIX

Disk Operating System (DOS)

What is DOS, and Why Learn About it?

• Microsoft developed (DOS), in 1981. DOS was designed for the IBM Personal Computer

• DOS is a collection of programs and commands used to control the overall computer operation in a disk-based system

• Three sections make up DOS: – Boot files – File management files – Utility files

What is DOS, and Why Learn About it?

• DOS is useful as a troubleshooting aid when Windows will not boot. It allows the hard drive to be accessed without the GUI and provides the ability to run troubleshooting or diagnostic programs.– DOS is a command line operating system, it is not

user-friendly

– DOS can only run one program at a time.

– DOS can only run small programs and has memory limitations

– DOS is an essential tool for IT professionals and is used extensively for troubleshooting

The DOS File Structure

• A file is simply a block of logically related data that is given a single name and treated as a single unit.

• Examples include programs, documents, drawings and other illustrations, sound files, etc.

• The common attributes for DOS files include:– Hidden File – Read Only – Archive (backup) status – System File

The DOS File Structure

• Hard drives organize the disk into directories and subdirectories. The main directory is known as the root directory.

• All other directories, if they exist, then radiate (branch out) from the root directory, similar to the branches of a tree.

• Locating any given file requires knowledge of the drive, directory, and subdirectory in which the file is found.

• The first hard drive in most computer systems is labeled “C”.

Overview of Basic DOS Commands

• Basic commands are generally internal and more advanced commands are usually external.

• The command line is the space immediately following the DOS prompt, C:\> where C:\ represents the hard disk drive root directory, and ">" is known as the prompt.

• A switch is added to the command by adding a space, a forward-slash (/), and a single letter.

Creating a DOS Boot Disk

• A DOS boot disk is a great tool to use to troubleshoot when the computer is not booting properly.

• A DOS boot disk is just a floppy disk with three necessary system files on it: – COMMAND.COM

– IO.SYS

– MSDOS.SYS

Booting the System with a DOS Disk

• A DOS boot disk is used to boot a computer to the DOS Prompt

• Insert a bootable disk in the floppy disk drive, and turn on the computer.

• The BIOS will execute the bootstrap program to move the master boot record into RAM and then begin loading the operating system.

• If the system performs a standard DOS boot up, it should print the Date and Time prompts on the monitor screen, followed by the command line prompt (A:\).

DOS Configuration Files

• In the MS-DOS operating system, there are two special configuration files, called CONFIG.SYS and AUTOEXEC.BAT.

• As the system moves through the steps in the boot procedure, the BIOS first checks in the root directory of the boot disk for the presence of the CONFIG.SYS file.

• Next, it searches for the COMMAND.COM interpreter, and finally looks in the root directory again for the AUTOEXEC.BAT file.

• Both the AUTOEXEC.BAT and CONFIG.SYS files can play significant roles in optimizing the system memory.

Editing System Configuration Files: SYSEDIT.EXE

• SYSEDIT is a standard text editor used to edit system configuration files such as Config.sys and Autoexec.bat.

• This utility can be used to edit the set of Windows initialization files generally referred to as INI files.

• INI files are basically text files that users can edit with a standard text editor utility such as SYSEDIT.

Memory Management

Memory Types

• The operating system that runs the computer uses physical memory (RAM), also known as system memory, and virtual memory.

• The four categories of system memory in the operating system include:– Conventional– Upper/expanded– High– Extended memory

Memory Types

• Conventional memory includes all memory addresses between 0 and 640KB.

• It is also known as base memory. This is the area where MS-DOS programs normally run.

Memory Types

• Upper Memory/Expanded Memory is also known as Reserved Memory

• It includes memory addresses that fall between 640KB and 1024KB (1MB).

• It follows conventional memory and has a size of 384KB.

Memory Types

• Extended Memory is memory locations beyond the 1 MB limit of the 8088/8086.

• This area of memory is also called Extended Memory Specification (XMS).

• XMS is the primary memory area used by Windows 9x.

Memory Types

• Once the XMS driver is loaded, extended memory becomes available to the OS.

• When this happens, the first 64KB of extended memory is called the High Memory Area (HMA).

Memory Management Tools

• There are several tools that can be used to manage and optimize system memory.– EMM386.EXE– HIMEM.SYS– DOS=HIGH– DEVICEHIGH/LOADHIGH

Other Types of Memory

• Two examples are RAM drive and virtual memory:• Virtual memory is used to describe memory that is

not what it appears to be. Hard disk drive space is manipulated to seem like RAM.

• It is the basis of multitasking in Windows 9x. Without virtual memory, it would be almost impossible to run most of the software in use today.

Memory Conflicts: GPF

• Memory conflict can lead to a condition called General Protection Fault (GPF).

• A GPF (“blue screen of death”) typically occurs when an application attempts to violate the system integrity by one of the following ways:– Tries to use a memory address or

space owned by another application – Tries to interact with a failing

hardware driver – Tries to have direct access to the

system hardware

Real Versus Protected Mode Memory Addressing

• Real mode means that software can address only 1,024 KB (1 MB) of RAM.

• Protected mode allows one program to fail without bringing down the whole system. What happens in one area of memory has no effect on other programs