Exam notes for A+ OS Exam A+
Operating
Systems
Technologies
A+
Certification awarded by CompTIA®
organization is the most widely recognized
certification in the area of PC hardware and
software technologies.
To attain A+ certification, one need
to pass 2 exams, namely, A+ Core Hardware
Technologies, and A+ Operating Systems
Technologies. These exams basically test the
skills in assembling a computer,
troubleshooting, and the ability to work
with various operating systems. Linux is not
included in A+, as it has an exam of its
own, offered by CompTIA®. 1.
IDE hard disks: -
An
IDE hard disk can have one Primary partition
and one Extended partition. An Extended
partition can be divided into one or more
logical partitions. After partitioning the
hard disk, each partition needs to be
formatted. -
The
File System Boot Sector is the first
physical sector on any logical volume. -
The
first physical sector on any bootable hard
disk contains Master Boot Record, MBR. -
The
command FDISK will destroy all the data on a
partition or drive on to which it is run. -
The
primary partition can be made bootable, by
marking partition as active. 2.
FAT: -
Windows
98 and Windows 95 OEM Release 2 support
FAT32. Note that Windows NT does not support
FAT32. NT supports only FAT16 and NTFS.
Windows 2000 supports FAT16, FAT32, and NTFS. -
DOS
standard FAT16 support drives up to 2 GB.
FAT32 supports drives up to 2TB (Terabytes). 3.
PC Utilities: The following DOS
utilities are useful in proper maintenance
of PCs. A.
SCANDISK: ScanDisk is a utility
program that was added to DOS Version 6.0.
SCANDISK is a better compared to CHKDSK.
SCANDISK can fix errors on data storage
devices such as hard disks, floppy disks,
RAM drives etc, and DoubleSpace compressed
drives. It analyzes and repairs damage to
the following: 1.
Physical clusters 2.
File allocation table (FAT) 3.
Lost clusters 4.
Cross-linked files 5.
Directory tree 6.
MS-DOS Boot sector 7.
DBLSPACE volume header, file
structure, compression structure. B.
CHKDSK (Check Disk): CHKDSK command,
one of DOS commands, examines your hard
drive for error conditions and reports the
total size of the disk, how many files are
stored there, and the space remaining.
CHKDSK also reports the total amount of
conventional memory in your system
and the amount of conventional memory
available. Note that CHKDSK can't report
extended memory. C.
DFRAG: The DFRAG.EXE is included with
DOS6.0 and later. DEFRAG utility arranges
the clusters of data on the hard drive to
achieve better performance by placing all of
the clusters for a given file together in a
contiguous order. DEFRAG does not do any
repair on your disk, and errors, if any will
remain on the disk. D.
BACKUP: DOS has a backup utility
since version 2.0. 4.
.COM, .EXE, .BAT files are executable
files. 5.
DOS Boot up:
A.
AUTOEXEC.BAT -
It
does: Modifies the PC environment (PATH,
SET, and other commands) -
Default
Attributes: Nil -
Is
it required for OS Start up: NO B.
CONFIG.SYS
1.
It does: Loads low level device
drivers and does performance tuning 2.
Default Attributes: Nil 3.
Is it required for OS Start up: NO C.
IO.SYS 1.
It does: Loads basics Input/ Output
routines for the processor 2.
Default Attributes: Hidden / System/
Read Only 3.
Is it required for OS Start up: YES
D.
MSDOS.SYS
2.
Default Attributes: Hidden / System/
Read Only 3.
Is it required for OS Start up: YES
E.
COMMAND.COM
2.
Default Attributes: Nil 3.
Is it required for OS Start up: YES 4.
Responsible for displaying the
command prompt in a DOS based computer. F.
HIMEM.SYS 1.
HIMEM.SYS must be loaded before
EMM386.EXE 2.
HIMEM.SYS is used to address the
extended memory G.
EMM386.EXE 1.
EMM386.EXE allows access to Upper
Memory Area. Please note that the
conventional memory of 1 MB is divided into
1. Lower Memory Area 640 KB, and 2. Upper
Memory Area 384KB
(1024KB-640KB). H.
ANSI.SYS -
The
files AUTOEXEC.BAT, CONFIG.SYS, ANSI.SYS
are not required for OS start-up.
However, the files IO.SYS, MSDOS.SYS,
COMMAND.COM are required for OS start-up. -
To
bypass the CONFIG.SYS, and AUTOEXEC.BAT
files during boot process of DOS, you need
to press F5. F8 allows you to selectively
bypass commands in AUTOEXEC.BAT, and
CONFIG.SYS. 6.
DOS allows you to set the following
attributes using ATTRB command: 1.
System 2.
Hidden 3.
Read-only 4.
Archive '+'
sets and attribute '-'
clears an attribute Examples: -
The
command ATTRIB +H myfile.txt will make the
file myfile.txt hidden. The other attributes
that can be set using ATTRIB command are
System, Read Only, and Archive. -
The
command ATTRIB C:\private.txt +h +r will
mark the file private.txt as both hidden and
read only. 7.
DOS, Windows3.1 Windows 95/ 98 operating
systems have the following characteristics: 1.
Each can have only one primary partition per
hard disk 2.
The primary partition is automatically
assigned a drive letter 3.
Each hard disk can have only one Extended
partition 4.
You can create one or more logical drives in
the Extended partition. 5.
The drive letters are assigned manually to
logical drives. 8.
The standard DOS partition cluster sizes are
as given below: 16MB-127MB:
2KB cluster size 128MB-255MB:
4KB cluster size 256MB-511MB:
8KB cluster size 512MB-1023MB:
16KB cluster size 1024MB-2048MB:
32KB cluster size Note
that due to DOS limitation, the FAT on each
hard drive partition can have 64K (65535)
individual addresses. Therefore, it is
clear, depending on the size of partition,
this number dictates the size of each
cluster. We arrive at 32KB cluster size by
dividing 2048(MB) with 64(KB). 9.
The Windows 95/98 system files include the
following: A.
IO.SYS B.
MSDOS.SYS C.
WIN.INI D.
COMMAND.COM E.
SYSTEM.INI F.
SYSTEM.DAT G.
USER.DAT -
MSDOS.SYS, WIN.INI, SYSTEM.INI
are text files. -
SYSTEM.DAT,
USER.DAT files are part of windows Registry
and can be edited using REGEDIT or REGDT32
utility. Registry files can't be read with
standard text editors. -
Further,
USER.DAT file corresponds to HKEY_LOCAL_USER
and SYSTEM.DAT corresponds to
HKEY_LOCAL)MACHINE.
10.
HKEY_LOCAL_MACHINE is the hive where the
information specific to the machine will be
stored. The information may include, network
settings, hardware drivers etc. HKEY_LOCAL_USER
hive stores data specific to user
configuration, such as desktop color
schemes, screen savers, wall paper, and user
specific application settings. 11.
Using FDISK, the following activities can be
carried out: 1.
Create Partitions: You can create
primary and extended partitions. Extended
partition holds one or more (Up to 23)
logical drives. 2.
Set Active Partition: FDISK allows
you to mark the primary partition as active
partition. 3.
Delete Partition: You can delete a
partition by using FDISK 4.
Display Partition Information. 12.
DOS COMMANDS: -
MEMMAKER
can be used to manage the system
memory optimally. Windows 95 and above
automatically manage the memory, where as
DOS requires manual memory management using
utilities like MEMMAKER. The DOS command MEM
can only display the contents of memory, but
itself can't manage the memory. -
When
you power on the DOS machine, you see a
message, "Starting MS-DOS". If you
press F5 key during this short period, you
can bypass AUTOEXEC.BAT and CONFIG.SYS
files. Given
below are common DOS commands that you use
frequently: 1. PATH: The command sets or displays a path for executable files. For example, "PATH=C:\; C:\DOS; C:\PROG; C:\MYFILES " command indicates DOS to first search ROOT, then C:\DOS, then C:\PROG, and finally C:\MYFILES for executable files. 2.
SET: Displays, sets, or removes DOS
environment variable. 3.
PROMPT: Changes the DOS command
prompt. The prompt can be made up of normal
characters and the following special codes:
$p
Current drive and path
$g
>(greater than sign)
$l
< ( less than sign)
$d
Current date
$t
Current time
$_
Carriage return
Syntax: PROMPT [text] For
example, to set the prompt to current date,
followed by the current drive path, issue
the command: PROMPT=
$p$d 13.
The file load order to start DOS is : -
IO.SYS -
MSDOS.SYS -
CONFIG.SYS -
COMMAND.COM -
AUTOEXEC.BAT -
Note
that CONFIG.SYS, and AUTOEXEC.BAT are
optional to load DOS. IO.SYS, MSDOS.SYS,
COMMAND.COM are required. 14.
When you format a disk with a "/s"
switch (say “format a:/s”), the
following files get transferred: 1.
IO.SYS 2.
MSDOS.SYS 3.
COMMAND.COM -
If
you want to format a drive and also make it
bootable, you need to format with /s switch. 15.
Windows 95: -
The
minimum published requirements for running
Windows 95 is 386 processor with 4 MB of
RAM. Though it may be sufficient, the
performance will be very poor and some
applications may not run at all. A
recommended configuration is a Pentium
processor with 32 MB of RAM. -
Booting
Windows 95 in safe mode loads the drivers
for Keyboard, Mouse, and standard VGA
graphics adapter. -
Windows
95 Version A supported only FAT16 file
system. The maximum hard disk partition
supported by FAT16 is only 2 GB. However,
Windows 95 Version B and Windows 98 support
FAT32 and therefore, can support partitions
upto 2TB (Tera bytes). -
SYSTEM.DAT
and USER.DAT comprise of Windows 95
Registry. These are the files where most of
the user and system configuration
information is stored. The Windows Registry
files are stored in \Windows directory by
default. -
Windows
95 makes a backup of the Registry after
every successful reboot. The Registry back
up files are named: USER.DA0, SYSTEM.DA0.
The original Registry files are named:
USER.DAT, SYSTEM.DAT. It may be noted, that
in the event of boot failure, you can delete
the original USER.DAT AND SYSTEM.DAT files
and the back up files can be renamed to DAT
files and the system can be rebooted
successfully. -
While
booting Windows 95, if you press F8, boot
menu will be displayed. Windows 95 provides
three different modes that the system can be
started. 1.
Normal Mode 2.
Safe Mode 3.
Command Prompt -
Normal
Mode is the mode Windows 95 starts by
default. It provides full functionality. -
Safe
Mode is a diagnostic mode of Windows 95 that
starts Windows 95 without any network, CD
ROM, and other drivers. The only device
drivers loaded in Safe mode are: o
Keyboard o
VGA
Display o
Mouse
Drivers -
Command
Prompt mode is provided to run some old DOS
applications that need to be run under DOS
only. These applications are primarily the
ones which access hardware, that Windows 95
does not allow to be accessed otherwise. Command
Prompt mode is also useful
for running FDISK and MSD. -
The
log file BOOTLOG.TXT records all the devices
and drivers that the Operating System
attempts to load. BOOTLOG records the status
of the devices and drivers. -
ScanDisk
can be used to check disk drives for errors.
The /f switch allows ScanDisk to
automatically fix the errors. -
HKEY_CURRENT_CONFIG
stores the hardware settings. The
six register keys available in Windows 95/98
Registry are: A.
HKEY_CLASSES_ROOT B.
HKEY_CURRENT_USER C.
HKEY_LOCAL_MACHINE D.
HKEY_USERS E.
HKEY_CURRENT_CONFIG F.
HKEY_DYN_DATA -
Adding
$ sign to the end of the share name makes
the share invisible over the network. 16.
Some important TCP/IP port numbers are as
given below: 1.
FTP: 21, stands for File Transfer
Protocol 2.
Telnet: 23, stands for Telnetting
from a remote terminal to a Telnet Server 3.
SMTP: 25, stands for Simple Mail
Transfer Protocol 4.
HTTP/WWW: 80, stands for Hyper Text
Transfer Protocol 5.
POP3: 110, stands for Post Office
Protocol 6.
HTTPS: 443, stands for HTTP Secure 17.
User level security gives better control of
resource on user-to-user basis. Share level
security assigns passwords to the resources
rather than the users and therefore less
secure. 18.
To pause the screen to view a large file,
use |more switch. For example, to view
autoexec.bat one screen at a time, type c:\autoexec.bat|more
at the DOS prompt. Space bar can be used to
go to next screen. 19.
DNS stands for Domain Name System Server.
DNS Server is the one responsible for
converting the Domain names to IP addresses. 20.
TSR stands for Terminate and Stay Resident.
An example of TSR program is a virus
detection program such as Norton Anti Virus.
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