NT Workstation

Chapter 1

Choosing An Operating System

 

Windows NT is just one of many operating systems developed by Microsoft.  Window NT is aimed at a business users who is interested primary in three things:

  1. Stability
  2. Security
  3. Accountability

 

Windows NT is stable in that it doesn’t crash with near the frequency of the other Windows operating systems like Win95/98 or Win 3.x.  This significantly improves productivity since you don’t have to wait for a reboot several times a day

 

Security was a major goal of NT.  Unlike the other versions of Windows, you MUST have a username and password to log onto NT.  If you don’t, you just don’t get in, period.

 

Accountability is related to the fact that after a user logs onto their computer, whatever they do can be tracked using something called “auditing”.  You can audit every activity a user does while they are logged on to their computer.  You can track every file they access, every program they open, and even wherever they go on the Internet.

 

But there are several versions of Windows NT.  The two that we’re interested in here is Windows NT Workstation and Windows NT Server.  One of the important questions we’ll have to answer for our customers is what version of NT do they need?

 

In order to decide what operating system to use, you have to take several considerations to task:

  1. What hardware do we have to work with?
  2. What type of security do we need?
  3. What software is in current use?
  4. What software to you WANT to use?
  5. What level of reliability and fault tolerance do you need?
  6. How response do you want the computer to be to the user?
  7. What type of interface do you want to work with?

 

First thing to look at is our hardward requirements.  These are the things you need to know:

 

Platform

Processor

RAM

Hard Disk

Windows 95

386DX-20

4MB (8 recommended)

40MB

Windows NT Workstation

486DX-33

12MB (16 recommended)

120MB

Windows NT Server

486DX-33

16MB

130MB

 

You need to know these numbers, especially the RAM requirements.  The amount of hard disk space required will vary, but the numbers here are good estimates.

 

How can you check to see if your system will have the right hardware to run Windows NT?  You can create and use a NT Hardware Qualifier Disk.  This is a disk you can use that will check the hardware on the computer and see if it will run NT.

 

The NTHQ uses something called the Hardware Compatibility List in order to see if the Hardware will run on NT.  This is a list that is updated constantly and you can see the most recent version on the Microsoft web site.  One limitation of the NTHQ is that it is only current as of 8/96.  You might have to check a more recent version of the HCL in order to really know if your hardware is compatible with Windows NT.

 

What is Windows NT?

  1. Robust
    This means it won’t crash easily
  2. 32bit
    It uses 32bit programming functions, rather than 16bit programming what was used in Win 3.x.  16bit programs are in general less stable and more likely to crash
  3. Uses Preemptive multitasking
    We’ll talk about this in a little bit
  4. Stable
    Won’t crash
  5. Flexible
    Can run programs made for other operating systems on Windows NT

 

What’s the difference between NT Server and NT Workstation?

è     NT Workstation
NTW is made to be a client operating system for Windows NT Server.  It is optimized for this role as a client so that it can accepted data and information quickly and reliably from NT Server computers

è     NT Server
NTS was created to be a Server Operating System.  This means that it has been optimized to function as a server or sharer of files and folders, printers and other devices.  People who are using client operating systems like NT Workstation can access information quickly and reliably from a NT Server computer.

 

Windows NT Features

è     Improved user interface
Windows NT uses the Windows 95 interface now.  Version 4.0. the one that we’re studying, is the first version of NT that uses the 95 interface.  This is a major improvement over the Win 3.x interface that had been used with earlier versions.

è     Portability
What is Portability?
This means that NT will run on many different hardware “platforms” or processors.  NT 4.0 will run on:
IBM Power PC
MIPS R4000
DEC Alpha AXP
Intel 386 and above processors

NT can do this because it is a “modular” operating system.  The hardware sensitive components are called the “Hardware Abstraction Layer”.  When NT is moved to another hardware platform, you just have to rewrite, or reprogram the HAL.  This is a LOT faster than having to rewrite the entire operating system for each processor you want to run NT on.

è     Multitasking
Multitasking is the ability to perform multiple tasks at the same time on the computer.  For example, you are multitasking when you are printing a report, downloading a file from the Internet, playing a music file from the CD ROM, and working on an Excel Spreadsheet, all at the same time.

There are two types of multitasking: Preemptive and Cooperative

Preemptive Multitasking
This form of multitasking allow the NT operating system to decide which programs get the attention of the processor.  No single program can monopolize the processor’s attention.  This prevents the system from locking up when a poorly written program hogs the processor’s attention.

Cooperative Multitasking
With this form of multitasking, its not the operating system’s job to make sure everyone has access to the processor when they need it.  Rather, it is the job of the individual programs that are using the processor at the time to release the processor’s attention so that another program can use it in order to run.  The problem is, a lot of programs are not written well, and so they don’t release the processor so that another program can use it.

The 16bit programs that are written for Win 3.x are based on the cooperative multitasking system.  That is one of the reasons why the system would lock up so much with Win 3.x; because programs would hog up the processor’s attention!


è     Multithreading Operations
Windows NT can run multiple threads simultaneously.  A thread is the smallest unit of computer code that can be scheduled for execution.  This is something worth remembering.

The ability to multithread means that NT can do multiple operations simultaneously, and it allows NT to use more than one processor at a time.

è     File Systems
A file system determines how the files and folders on the computer are stored.  Just like a regular file cabinet, some filing systems are more efficient than others, some are more security than others, and some are more reliable than other.  The same applies to the files systems that are used on the computer.  The are two main types of filing systems that are used by Windows NT:  The FAT (File Allocation Table) file system, and the NTFS (New Technology Filing System).  Each has its own advantages and disadvantages.

FAT
This is the file system that we know from DOS, Win 3.x and Win 95/98.  FAT has been used for a long time.  We’ll take later about FAT in more detail.

NTFS
This file system was introduced with Windows NT. It has a lot of advantages over FAT in terms of increased security and reliability. We’ll take more about this later.


è     Security
This is one of the most important aspects of NT.  Microsoft wanted to sell NT to the military and developed NT so that it would meet Govt. C2 specifications.

è     Support for many clients
NT can support many different operating systems are clients computers:
Windows 3.x
DOS
Win95/98
Macintosh
OS/2
Windows NT Workstation

This means that NT Server will support these computers “out of the box”; you don’t need to buy any other software to connect these computers to a Windows NT Server computer.

è     Multiprocessor Support
When you processor is overwhelmed, and not powerful enough, there are two things you can do:
1. Get a faster processor
2. Add more processors

Windows NT is the only Microsoft operating system that will allow you (support) more than one processor in a single computer.

Windows NT Workstation will allow you to have 2 processors in a single computer “out of the box”

Windows NT Server will allow you to have 4 processors in a single computer “out of the box”

You can get special versions of “HAL” that would allow you to have as many as 32 processors in a single Windows NT machine (either Server or Workstation).

è     Compatibility with Applications
Windows NT is flexible in that you can run programs that we designed for other operating systems. These types of programs can be run on Windows NT:

DOS 16-bit applications
Win 3.x 16bit applications
POSIX.1 applications (POSIX is a UNIX like OS that is used by the fed govt.)
OS/2 1.x character based applications (and OS/2 Presentation Manager apps)
Win32 applications which are 32bit applications created for NT, Win 95/98


è     Storage Space
Windows NT allows you to store AMAZING amounts of information on your computer.  Windows NT allows you to use up to 4 GIGABYTES of RAM!

Windows NT also allows you to create partitions or files up to 16 EXABYTES large!


è     Network Connectivity
Windows NT supports these networking protocols right out of the box:

TCP/IP
DLC
NetBEUI
AppleTalk
NWLink

Using these network protocols (or languages), we can connect to other types of networks, such as:

Appletalk (Macintosh) Networks
Banyan Vines
DEC Pathworks
IBM LAN Server
IBM SNA Networks
Microsoft LAN Manager
Win95/98 Peer to Peer Networks
Microsoft Windows for Workgroups Networks
Novell NetWare
TCP/IP networks (most important of which is the Internet)

Windows NT Architecture

 

Remember I said earlier that NT was a modular operating system?  Well, now its time to see what those modules are!

 

There are two major “modes”: User Mode and Kernel Mode.

 

The User Mode

 

The user mode is the part of the operating system that is responsible for running user programs or applications.  The main thing to remember about the user mode “processes” is that they have NO ACCESS TO THE HARDWARE of the computer.  All user mode applications must ask the permission of the Kernel mode services if they can use parts of the computer hardware to do the things they need to do.

 

They did it this way in order to let the Kernel mode “executive services”  be in control of the hardware.  In this way, all hardware components of the computer, like the hard drive, the modem, the CD ROM, the RAM and everything other hardware component is protected from programs that are not written well and might take control and lock up the computer.

 

Two important “subsystems” run inside of the User Mode: the Environment Subsystems and the Security subsystem.

 

  1. Environment Subsystems
    It is the environment  subsystems that trick programs into thinking they are running on another operating system.  For example, if you want to use a program that was designed for POSIX.1, the POSIX.1 program would start in the POSIX subsystem.  As for as the POSIX program is concerned, it is running in POSIX and not Windows NT.

    The POSIX subsystem is responsible for running programs developed for POSIX.1

    The OS/2 subsystem is responsible for running programs designed for OS/2 version 1.x

    The Win32 subsystem is responsible for programs designed for Win95/98, Win 3.x and Windows NT programs.

    It is the job of the environment subsystem to ask the permission of the executive services (which we’ll get to in a little bit) to access the hardware.

  2. Security Subsystem
    This is responsible for the log on process.  What does it do?

    You enter your password to log on.  The security subsystem then sends an “authentication package” to the security reference monitor which lives in the Kernel Mode.  If the password is correct for the user, the security reference monitor will send back to the security subsystem an “access token”.  This access token contains important information about the permissions and groups memberships of the user logging on.

 

Kernel Mode

 

The Kernel mode processes are also called the “Executive Services”.  These are the main bosses of the operating system.  No user mode process, no program that the user can interact with, can do anything without the permissions of the “Executives”.

 

Kernel Mode processes have priority over the processor at all times, so that when they need to do something important, they can “grab” the processors attention whenever they like.  Kernel mode processes have priority of the RAM of the computer too.  They will not be “swapped” out to disk (will take about the SWAP or pagefile later, which is an extension of RAM on the hard drive of the computer).

 

There are 3 modules in the Kernel Mode:

  1. The NT Executive
  2. The Kernel
  3. The HAL

 

However, when we’re talking about all the modules at the same time, we refer to them all as the “Executive Services”.  These are the “bosses” of the NT operating system.

 

You don’t have to memorize all the different Executive Services.  Just be aware of their general function, which is to maintain the integrity of the operating system by protecting the hardware from the evils of the unruly user mode processes.

 

There is ONE thing THAT I REALLY WANT YOU ALL TO REMEMBER:

 

HAL PROTECTS THE HARDWARE AND PREVENTS PROGRAMS FROM DIRECTLY ACCESSING OR TALKING TO THE HARDWARE.

 

 

Windows NT Memory Architecture

 

Remember that RAM is the computer’s “active memory”.  In order to work on anything, the information must be in RAM. It’s sort of like the computer’s “conscious memory”. You have to be conscious of something in order to think about it.  Information has to be in the computer’s RAM in order for it to think about it and work with that information.

 

Windows NT uses something called a “virtual memory model”.  If you have worked with DOS, you are probably aware that memory was split up into three different areas or types: low memory, high memory, and extended or expanded memory.  This caused a LOT of problems for people who wanted to do a lot of multitasking in Win 3.x and even to some extent in Win 95.  With the virtual memory model, all memory looks the same to Windows NT.

 

So, while all memory “looks the same” to NT, its not physically the same.  Memory is usually considered to be RAM.  However, if NT needs more memory to run applications and open files, it can trick programs into thinking that it has more RAM than it really has.  That “trick” memory is called virtual or “paged” memory.

 

When there isn’t enough physical RAM to hold all the information the computer needs, what it will do is move some of the information that isn’t being used at the moment from physical RAM to the hard drive, into a file called “pagefile.sys”.  This is an extension of the physical RAM which is kept on the hard drive.

 

Now, if the computer needs the information in the virtual RAM in the pagefile, what it does it “swap out” some information that is in RAM to the pagefile and gets the stuff it needs off of the pagefile and puts it back into physical RAM.

 

In Windows NT we call this virtual memory file the pagefile.  There is also virtual memory in Win 3.x and Win95, but in those operating systems the virtual memory file is called the “swap” file.

 

While its nice to be able to trick applications into thinking they have more RAM available than we actually have (because we can open more programs at the same time), the drawback is that paged memory is MUCH SLOWER.  You might notice sometimes that the hard drive seems to crunch and crunch when you try to open a program or file.  That is because there isn’t enough physical RAM, so its swapping information in and out of the pagefile in order to make room in RAM for the program you want to open up.

 

32bit, Flat, Linear Addressing

This just means that memory isn’t broken up into low, high, upper and extended memory like in DOS based operating systems.  This helps make programs more stable and prevents the system from crashing so much.

 

What are the differences between NT Server and NT Workstation?

 

I’m glad you asked, because you need to know this for you exams and in your computer practice as well.

 

è     NT Server allows an unlimited number of client computers to connect to it
NT Workstation allows only 10 computers to connect to it at a time

è     NT Server supports 4 processors “out of the box”
NT Workstation supports 2 processors “out of the box”

è     NT Server allows up to 256 connections to it via RAS (we’ll talk about RAS later)
NT Workstation allows only 1 connection to it via RAS

è     NT Server can both import and export using the Replicator Service
NT Workstation can only import using the Replicator Service
(we’ll get to the replicator service later too)

è     NT Server support MACs, logon validation, and disk fault tolerance
NT Workstation doesn’t do any of those things J

 

Now answer the questions at the end of the chapter and let me know if there are any that you don’t understand!