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Computer Hardware Online |
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OS Components: A+ Certification Essentials
OS Components
In the previous section, you had a great opportunity to
review the similarities and differences between Microsoft Windows, Mac OS X,
and Linux. In this section, we start really exploring the internals of
Microsoft Windows. Most of the exam covers Microsoft Windows as it is by far
the largest install base and is most likely the OS you will work on frequently
in your next job as a computer support technician or network administrator.
This section provides us an opportunity to review the
components that provide the core services of the OS to run. In later sections,
we look at more of the “front end” pieces of the operating system – such as
Windows Explorer, My Computer, the Control Panel, and the command prompt. This
section provides detail on the innards of the OS and how it all works
together.
Core Services
Microsoft Windows is a very complex operating system with
millions of lines of code. It has to be – just think of all of the different
types of computers and components out there Microsoft has to support. With
millions of different combinations of motherboards, hard drives, accessories,
and software applications, Microsoft has a tremendous job to produce a stable
OS which doesn’t crash at a moment’s notice.
I could insert a joke here about Windows crashing, but just
think about the stability of your computer systems over the past few years. I
very infrequently have my laptop suffer a crash – in fact, I can’t remember
the last one I had.
The core services in Microsoft Windows are the
file system, virtual
memory, and the registry.
File System
The File System is responsible for managing all of the
storage system activities. Windows NT based Operating Systems such as Windows
2000, XP, and Vista have two primary file systems available: FAT and NTFS. The
Installable File System (IFS) Manager in the I/O Manager is responsible for
managing file systems.
On FAT systems, it has two partition types available for
each hard drive: primary and extended. A primary drive partition is what is
commonly referred to as the “C:” drive. Up to 23 logical drives can exist in
the extended partition – allowing you to partition one physical drive into
several “drives” on your computer – e.g. C:, E:, F:, etc.
The active partition is
the logical drive the system will boot up to. The system files need to be
located on this partition and it must be set to active for the system to
properly boot. The active partition must be the primary partition in a FAT
system.
NTFS differs in many ways from FAT. NTFS can have up to
four primary partitions or three primary partitions and one extended
partition. Primary partitions can be marked as active in NTFS system.
One hard drive only supports up to 32 primary partitions
plus logical drives.
Virtual Memory
PCs are often limited by the amount of physical RAM (Random
Access Memory) they contain. Often, Windows requires more memory than the
system physically has to open all of the applications and services you want to
run. The Operating System exceeds the physical limits of the system by
providing virtual memory, or memory space
which is swapped back and forth to your physical hard disk. Later, you will
learn about the paging file and how this swap occurs from physical memory to
the hard disk.
Figure 27: Windows Task Manager
The Windows Registry
The Registry
In the days before Windows 9x, system and application
settings were stored in .ini files. With a few applications, the OS could get
away with managing a couple .ini files, but can you imagine doing that now?
With dozens of applications installed on a given machine and thousands of
potential preferences and settings, not to mention multiple users on each
machine, the OS would not be able to manage the potentially thousands of
settings files.
Enter the registry, a
database containing all of those application settings and user preferences
stored in a hierarchal structure. Understanding how the registry works – and
what you can and can’t do in it – will be crucial to your role as a computer
support technician. Since the registry is such an integral part of the
Operating System, changing it manually can cause major problems – including a
non-booting system.
Likewise, if parts of the registry become corrupt, it can
also cause major problems which you will learn more about in the
troubleshooting sections of this free tutorial.
Figure 28: The Registry Editor - One Way to Edit the
Registry
The Registry is divided into five sections:
1. HKEY_CLASSES_ROOT (HKCR)
2. HKEY_CURRENT_USER (HKCU)
3. HKEY_LOCAL_MACHINE (HKLM)
4. HKEY_USERS (HKU)
5. HKEY_CURRENT_CONFIG (HKCC)
Each of these five sections has a specific purpose for the
operation of Windows.
HKEY_CLASSES_ROOT
HKEY_CLASSES_ROOT, sometimes abbreviated HKCR, is really a
subkey of HKEY_LOCAL_MACHINE\Software. This key ensures that the proper
application opens when you double-click on a file in Windows Explorer. For
example, if you open your C: drive and double-click on a .xls file, Windows
looks at HKEY_CLASSES_ROOT to see what application .xls files are associated
with, finds out that it is Microsoft Excel, and then opens Microsoft Excel to
view the file.
HKEY_CURRENT_USER
HKEY_CURRENT_USER contains the root of configuration
information for the user who is currently logged on. The information is the
settings, user’s folders, configuration options, and user’s profile. This key
is frequently abbreviated as “HKCU.”
HKEY_LOCAL_MACHINE
One of the most frequently accessed areas in the registry,
HKEY_LOCAL_MACHINE (HKLM) contains the configuration information for the
entirely computer – applicable for any user.
HKEY_USERS
HKEY_USERS, sometimes abbreviated HKU, contains the
configuration information for each of the user profiles on the machine.
HKEY_CURRENT_CONFIG
Contains information about the hardware profile that is
used by the local computer at startup.
Registry Files
Unlike a traditional database, the registry is not stored
in just one file. There are several files (and supporting files) which make up
a registry. In Windows NT 4, Windows 2000, Windows XP, and Windows Server
2003, the registry files (other than HKEY_CURRENT_USER) are located in
Systemroot\System32\Config, for example, on my system that is
c:\windows\system32\config. The following files make up the sections of the
registry:
|
Registry hive |
Supporting files |
|
HKEY_LOCAL_MACHINE\SAM |
Sam, Sam.log, Sam.sav |
|
HKEY_LOCAL_MACHINE\Security |
Security, Security.log,
Security.sav |
|
HKEY_LOCAL_MACHINE\Software |
Software, Software.log,
Software.sav |
|
HKEY_LOCAL_MACHINE\System |
System, System.alt, System.log,
System.sav |
|
HKEY_CURRENT_CONFIG |
System, System.alt, System.log,
System.sav, Ntuser.dat, Ntuser.dat.log |
|
HKEY_USERS\DEFAULT |
Default, Default.log,
Default.sav |
Table 2: Registry File Locations, retrieved from
http://support.microsoft.com/kb/256986/
The HKEY_CURRENT_USER supporting files are located in the
user profiles, often located at C:\WINNT\Profiles\Username\, C:\Documents and
Settings\Username\, or C:\Users\Username\ depending on the OS.
Classic
Windows: In Windows 98, the registry files are name User.dat and
System.dat. In Windows ME, the files are Classes.dat, User.dat, and System.dat.
Backing Up the Windows Registry
Backing Up the Registry
It’s very important to backup the registry before you make
any changes as you can seriously damage your computer system if you make a
mistake.
We recommend using Windows Backup or an industry standard
backup software application to keep your system backed up on a regular basis.
Since we also know that hardly anyone does this, it’s important to know how to
backup your registry before making any changes.
Manual Steps to
Export Registry Subkeys
If you are editing a single subkey in the registry, it may
make sense just to backup that subkey versus the whole registry. Follow these
steps to backup a subkey:
1. Click
Start, and then click
Run.
2. In the
Open box, type regedit, and then click
OK.
3. Locate and then click
the subkey that contains the value that you want to edit.
4. On the
File menu, click Export.
5. In the
Save in box, select a location where you want to save
the Registration Entries (.reg) file, type a file name in the
File name box, and then click
Save.
Do not use this process if you want to backup an entire
area of the registry, for example all of HKEY_CURRENT_USER. Instead, follow
the next process and use Windows Backup to backup the registry.
Backing Up the
Registry Using Windows Backup
1. Click
Start, click
Run, type
ntbackup.exe, and then click
OK.
2. On the "Welcome to
the Backup and Restore Wizard" page, click
Advanced Mode.
3. Click the
Backup tab.
4. On the
Job menu, click
New.
5. Click to select the
check boxes for the drives that you want to back up. If you want to be more
specific in your selections, expand the drive that you want, and then click to
select the check boxes for the files or for the folders that you want.
6. Click to select the
System State
check box.
7. If you want to back
up system settings and data files, back up all the data on your computer plus
the System State data. The System State data includes such things as the
registry, the COM+ class registration database, files that are under Windows
File Protection, and boot files.
8. In the
Backup destination
list, click the backup destination that you want to use.
9. If you clicked
File in the
previous step, click Browse,
and then select the location. You can specify a network share as a destination
for the backup file.
10. On the
Backup tab,
click Start Backup.
The Backup Job Information
dialog box appears.
11. Click
Advanced.
12. Click to select the
Verify data after backup
check box.
13. In the
Backup Type box,
click the type of backup that you want. When you click a backup type, a
description of that backup type appears under "Description."
14. Click
OK, and then
click Start Backup.
A Backup Progress
dialog box appears, and the backup starts.
15. When the backup is
complete, click Close.
16. On the
Job menu, click
Exit.
Backing Up the
Registry in Windows Vista
Windows Vista streamlines the backup process and provides a
single full computer backup interface.
Figure 29: Windows Vista Backup and Restore Center
The Backup and Restore Center (available under All
Programs\Maintenance or the Control Panel) has several options to backup your
computer. You can select to just backup your files or the entire computer.
Additionally, if you select Backup Status and
Configuration under the All Programs\Accessories\Tools menu on the
Start menu, you can setup automatic backups to occur at some frequency.
These options eliminate some of the advanced settings you
could do under previous versions of Windows, but reduces complexity
significantly for most users.
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