Dos1

0- clock; 040-05F

1- keyboard; 060

2- goes to IRQ 9; 0A0

3- COM 2,4; 2F8-2FF

4- COM 1,3; 3F8-3FF

5- sound card or LPT2

6- floppy disk.

7- LPT1

8- real Time Clock

9- usually available.

DEFINITIONS:

	Cooperative Multitasking- depends on the application itself to be responsible for using and then freeing access to the CPU.
	Pre-emptive Multitasking- The operating system allots each application a certain amount of processor time and then forcibly takes back control.
	Transient commands (external)- Commands that are in the DOS directory.
	Resident commands (internal)- Commands that are within COMMAND.COM

W95 INFORMATION:

BACKUP(S):

	There are basically two types of virii: Benign and Malicious.
	W95 backup supports very few tape drives- Only QIC 40, 80, & 3010.
	To make a startup disk- start>settings>control panel>add remove programs>Startup and disk tab.
	Full Backup- backs up all files.
	Differential- backs up files that have changed from the last full backup (the differential disk gets bigger and bigger each day).
	Incremental- backs up the files each day that have changed since the last backup (Not necessarily the last FULL backup). This requires more disks each day.

FILE TYPES:

	KERNEL32 handles memory management, file I/O operations, and application execution. This is the heart of the OS.
	GDI.EXE (Graphical Device Interface) and GDI32.DLL file(s) control and creates the GUI interface and also handle printing. GDI.EXE is a set of text and graphics display routines that Windows programs call when needed for graphical screen output. This set of routines is called a library. Programs do not need to do special graphics programs because the display routines are already available. It is responsible for drawing windows and scroll bars.
	USER.EXE is the Windows input and output manager. The types of input managed include keyboard, mouse, and communications, such as ports. The output managed includes sound and communications hardware. Also manages user windows and profiles.
	IO.SYS is a W95 environmental file.
	SYSEDIT.EXE loads protocal.ini, system.ini, win.ini, config.sys, autoexec.bat.
	DETCRASHLOG.TXT is created as an error log when installing W95.
	SYSTEM.DAT & USER.DAT are the two W95 registry files. SYSTEM.DAT contains system settings and application settings. USER.DAT has settings for individual users. The back-up of these files are SYSTEM.DA0 and USER.DA0.

MISC:

Registry

	HKEY_CLASSES_ROOT- file extension associations.
	HKEY_CURRENT_USER- profile information and preferences.
	HKEY_LOCAL_MACHINE- settings and information for hardware.
	HKEY_USERS- default user and current user profile.
	HKEY_CURRENT_CONFIG- current hardware configuration.
	HKEY_DYN_DATA- dynamic settings for Plug N' Play devices.
	WIN95 does not need MSDOS.SYS. Because some older programs require MSDOS.SYS to exist, a dummy file MSDOS.SYS exists in WIN95. In WIN95 the functions found in IO.SYS, MSDOS.SYS, IFSHELP.SYS, and SETVER.COM are now all in IO.SYS.
	A memory leak happens when a program does not release all of it’s allocations when it ends.
	The exception error codes for memory and video problems in W95 are 0E and 0D.
	The System and GDI heap can fill up and cause memory errors.
	W95 handles caching with VCACHE.
	Peer-To-Peer: Each PC acts as a workstation and a server.
	Windows has a 255 character limit on filenames.
	16bit code is slower than 32bit code because the CPU must run in REAL MODE.
	F4 when Starting Windows 95... will load the previous OS.
	A Trojan horse appears to be a normal program.
	Printer spooling sends the print job to SPOOL32.EXE and is printed in the background so the program can finish printing sooner.

DOS/WIN31:

Memory Related

	0-640KB Conventional Memory
	640KB-768KB Video RAM
	768-960KB BIOS and RAM buffers
	960-1024KB Motherboard BIOS
	Expanded memory has no direct memory address. It resides on an add-in card and is swapped in and out of memory space based on the control of the expanded memory manager. Extended memory actually has addresses associated with it, because the new CPUs have more address lines. WIN95 users flat memory, which is obviously better.

Files:

	Permanent swap files are created by Windows the first time it is started. It consists of 2 files: SPART.PAR and 386SPART.PAR. SPART.PAR points to the location of the actual swap file. Temporary swap files are created every time you start windows. It is named WIN386.SWP Permanent swap files are more efficient because the use contiguous disk space and cannot be on a compressed drive.
	VMM32.EXE loads immediately after WIN.COM executes.
	HIMEM.SYS creates and manages the Extended High Memory Area. DOS programs need a contiguous memory space, but it does not have to be in conventional memory.
	EMM386.EXE provides the operating system with a mechanism to see extended memory, on a 386+ computer system, as if it were expanded memory. The memory space that EMM386.EXE controls is upper memory.
	DOS has an imposed memory limitation of 640KB and a programming structure that is based on segmented memory. Most people are no longer interested in dealing with its limitations.
	REG.DAT is the W31 registry file.
	O.SYS is the start-up file.

MISC:

An Intel compatible processor has three modes of operation: Real, Protected, and Enhanced.

	Real mode places the processor in an 8088-emulation mode. This mode is slow and is limited to 1MB of address space.
	Protected Mode of the CPU allows the use of up to 16MB of RAM. DOS won't run in protected mode, but Windows will and some other operating systems.
	Virtual Mode allows the processor to pretend that it is a multiple of 8086 or 8088 processors. Each has the same restrictions as it's counterpart mode.
	If W31 set-up hangs, restart installation, restart system, then RUN SETUP /I (Ignore device errors).
	DEVICEHIGH places a driver into upper memory / LOADHIGH places DOS into upper memory.
	The SET command will check the DOS environment. SHELL=COMMAND.COM /P /E:2048.
	If NWCLIENT or LM directories are on the HDD, the DOS system is probably networked.
	When a hardware interrupt occurs, try increasing the STACK size in the CONFIG.SYS.
	When Starting MD-DOS: F5 will clean boot; F8 will go step-by-step.
	There is a 512-file limit for the root directory.
	A clean boot is a boot without a CONFIG.SYS or AUTOEXEC.BAT

	The DOS kernel is composed of two files. IO.SYS and MSDOS.SYS. IO.SYS is a piece of programming code that allows the rest of DOS and programs to interact directly with the system hardware and the system BIOS. It also has built in drivers for such things as printer ports, serial or communication ports, floppy drives, hard drives, console I/O, etc. MSDOS.SYS handles disk I/O. IO.SYS and MSDOS.SYS are loaded into memory at boot-up and stay there at all times.

	If a user forgets their password in WIN31, go to the CONTROL.INI file and delete the [ScreenSaver] section.
	Order of execution for MS-DOS: IO.SYS, MSDOS.SYS, CONFIG.SYS, COMMAND.COM, AUTOEXEC.BAT.
	DLL files are small pieces of executable code that is shared between files to help reduce program size.
	DOS (FAT16) supports up to 2gig partitions. Win 95 SR2 (FAT32) can see up to 2,048GB or 2TB.
	Aggressive memory searching looks for spots within a memory range reserved for a BIOS chip.
	Write-back cache is a little risky because a user may power off before the writing takes place.
	WIN.INI contains personalized settings, and various programs use settings within it also.
	In .INI files, LOAD=xxxxxxx.xxx will start minimized; RUN= will start as regular full screen.
	PROGMAN.INI, CONTROL.INI, and COMMAND.COM cannot be edited with sysedit.
	TrueType allows screen fonts to more closely resemble actual printed fonts.
	[COMMON] in CONFIG.SYS executes regardless of menu options chosen.
	PC-DOS uses: IBMBIO.COM, IBMDOS.COM and COMMAND.COM
	Startup of a computer is referred to as booting or boot-strapping.
	MORE is an external command, PAUSE is an internal command.
	HIMEM.SYS controls access to HMA (High Memory Area)
	DRVSPACE is used in DOS-WIN98 for Drive compression.
	BUFFERS=xx should be reduced if SMARTDRV is loaded.
	BUFFERS= and SMARTDRV are both used for caching.
	SHARE.EXE provides file and record locking functions.
	Semi-colons work as comment flags in .INI files.
	TTF are True Type Font files.
	MSAV.EXE is MS Anti-virus.
	SYSETEM.INI is the primary configuration file for hardware settings. It contains the console input and output devices (keyboard and monitor), the mouse, ETC... CONTROL.INI controls settings within the Control Panel
	The HDD is managed and allocated in clusters. FAT16= 32KB clusters; FAT32=4KB clusters. A group of clusters is called a chain.
	The Scheduling option in Win 3.1 determines how much of the system's resources are dedicated to foreground applications.
	MFM and RLL drives are affected by changes in temperature and require low level formats. RLL drives use built in data compression.
	Interleave (EX 1:1 or 1:2) is a way of enabling the hard drive circuitry is able to transfer information fast enough.
	In .INI files [Example] is called sections, and under them are called entries. Entries have two parts- an entry name and a value.
	Logical Sectors are like pieces of the pie and Tracks are pieces of slices that get smaller as they are cut towards the middle.

TROUBLESHOOTING STEPS:

	Step 1: Talk to the Customer - Find out the problem, believe the customer but use hidden skepticism.
	Step 2: Gather Information - Probe the customer for anything they might not be telling you. Dropped equipment? New hardware? Did it ever work?
	Step 3: Eliminate Possibilities - Strip down all non-essential components.
	Step 4: Document Your Work- If the process of elimination goes beyond 2 or 3 elements, start writing it down.

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Last modified 12/23/2005 20:37

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