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).
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3. PC Utilities: The following DOS utilities are useful in proper maintenance of PCs.
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:
Physical clusters
File allocation table (FAT)
Lost clusters
Cross-linked files
Directory tree
MS-DOS Boot sector
DBLSPACE volume header, file structure, compression structure.
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.
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.
BACKUP: DOS has a backup utility since version 2.0.
4. .COM, .EXE, .BAT files are executable files.
5. DOS Boot up:
IMPORTANT DOS FILES USED DURING BOOT UP ARE:
AUTOEXEC.BAT
It does: Modifies the PC environment (PATH, SET, and other commands)
Default Attributes: Nil
Is it required for OS Start up: NO
CONFIG.SYS
It does: Loads low level device drivers and does performance tuning
Default Attributes: Nil
Is it required for OS Start up: NO
IO.SYS
It does: Loads basics Input/ Output routines for the processor
Default Attributes: Hidden / System/ Read Only 3. Is it required for OS Start up: YES
MSDOS.SYS
It does: Defines System File locations
Default Attributes: Hidden / System/ Read Only
Is it required for OS Start up: YES
COMMAND.COM
It does: The file contains internal command set and error messages
Default Attributes: Nil
Is it required for OS Start up: YES
Responsible for displaying the command prompt in a DOS based computer.
HIMEM.SYS
HIMEM.SYS must be loaded before EMM386.EXE
HIMEM.SYS is used to address the extended memory
EMM386.EXE
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).
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:
System
Hidden
Read-only
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:
Each can have only one primary partition per hard disk
The primary partition is automatically assigned a drive letter
Each hard disk can have only one Extended partition
You can create one or more logical drives in the Extended partition.
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:
IO.SYS
MSDOS.SYS
WIN.INI
COMMAND.COM
SYSTEM.INI
SYSTEM.DAT
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:
Create Partitions: You can create primary and extended partitions. Extended partition holds one or more (Up to 23) logical drives.
Set Active Partition: FDISK allows you to mark the primary partition as active partition.
Delete Partition: You can delete a partition by using FDISK
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:
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.
SET: Displays, sets, or removes DOS environment variable.
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
$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:
IO.SYS
MSDOS.SYS
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.
Normal Mode
Safe Mode
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:
Keyboard
VGA Display
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:
HKEY_CLASSES_ROOT
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
HKEY_CURRENT_CONFIG
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:
FTP: 21, stands for File Transfer Protocol
Telnet: 23, stands for Telnetting from a remote terminal to a Telnet Server
SMTP: 25, stands for Simple Mail Transfer Protocol
HTTP/WWW: 80, stands for Hyper Text Transfer Protocol
POP3: 110, stands for Post Office Protocol
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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