CompTIA^® A+ Operating Systems Exam Cram Notes

• 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
• $g >(greater than sign)
• $l < ( less than sign)
• $d Current date
• $t Current time
• $_ Carriage return

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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