Windows Software Basics

File Location Platforms

• FAT/FAT32
  Short for File Allocation Table, the FAT is a table the operating system uses to locate files on a disk. Due to fragmentation, a file may be divided into many sections that are scattered around the disk. The FAT keeps track of all these pieces.

  Windows 95 Original used VFAT (virtual file allocation table). Windows 98 and later versions of Windows 95 (OSR 2.1 and above) use both FAT and FAT32 formats. FAT32 is a newer version of the file allocation table that increases the number of bits used to address clusters and also reduces the size of each cluster. The result is that FAT32 can support larger disks (up to 2 terabytes) and better storage efficiency.
  
  

• NTFS
  Short for NT File System, NTFS is one of the file systems for the Windows NT operating system (and NT based systems Win 2000 and Win XP). These operating systems also support the FAT file system. NTFS has features to improve reliability, such as transaction logs to help recover from disk failures. Additionally, NTFS provides compression and encryption features for improved file system security. Hard drives formatted as NTFS can see FAT and FAT32 drives, but FAT32 drives cannot see NTFS formatted hard drives.

BIOS
Short for Basic Input/Output System, the BIOS is built-in software that determines what a computer can do without accessing programs from a disk. On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications and many miscellaneous functions. The way to access a computer's BIOS differs amongst various manufacturers, but it can usually be done by pressing the DEL key, CTRL+ALT+ENTER, or a function key such as F2 during startup. Checking the BIOS is a key component of troubleshooting a PC.

POST
POST stands for Power-On Self Test. The POST is a series of diagnostic tests that run automatically when you turn on your computer. The actual tests can differ depending on how the BIOS is configured, but usually the POST tests the RAM, the keyboard and the disk drives. If the tests are successful, the computer boots itself. If the tests are unsuccessful, the computer reports the error by emitting a series of beeps and possibly displaying an error message and code on the display screen. The number of beeps indicates the error but differs from one BIOS to another.

Registry
The registry is a database used by the Windows operating system to store configuration information. The registry consists of the following major sections:

• HKEY_Classes_Root
  This section contains file associations and OLE information. OLE (Object Linking and Embedding) is a standard developed by Microsoft which allows you to link or embed an object created with one application in a second application.
  
  
• HKEY_Current_User
  As its name implies, this section holds all preferences set for the current user.
  
  
• HKEY_Local_Machine
  The settings for hardware, operating system, and installed applications are stored here.
  
  
• HKEY_Users
  All the user information for each user of the system is stored here.
  
  
• HKEY_Current_Config
  This section contains settings for the display and printers.
  
  
• HKEY_Dyn_Data
  Performance data is stored in this section.
  
  

Most Windows applications write data to the registry, at least during installation. You can edit the registry directly by using the registry editor provided with the operating system (go to Start -> Run and type regedit). However, you must take great care; errors in the registry could disable your computer. If you are not comfortable making changes to your registry, schedule an appointment with the Help Desk or request a visit from Software Support.

System Files
System files are installed by an operating system so that it may function. The system files can be accessed by runing sysedit from Start -> Run. On Windows 98, ME and XP, you can edit these files with a checkbox interface by running msconfig from Start -> Run. Note that not every version of Windows uses the same system files in the same ways (some versionf of the operating system do not use all of the example files listed below). Examples include:

• Autoexec.bat
  Autoexec.bat is an automatically executed batch file, executed by DOS when a computer boots up. This file is a convenient place to put commands you always want to execute at the beginning of a computing session. This file is not used by newer versions of Windows.
  
  
• Config.sys
  Config.sys is a configuration system file. Whenever a DOS computer boots up, it reads the Config.sys file (if it exists) and executes any commands in it. The most common commands are BUFFERS= and FILES=, which enable you to specify the buffer size and the number of files that can be open simultaneously. Config.sys is not used by newer versions of Windows.
  
  
• Protocol.ini
  This file contains hardware information to configure ethernet cards and software information to configure communications protocols (TCP/IP, IPX/SPX and NetBEUI).
  
  
• System.ini
  System.ini is a file that initializes drivers, DLLs (explained below) and password lists needed to start up the system. Like all INI files, it is only needed for compatibilty with 16-bit applications.
  
  
• Win.ini
  Win.ini is an initialization file located in the Windows folder. Almost all settings in Win.ini can be changed in the control panels and are retained in Win.ini purely for compatibility reasons.
  
  

DLL Files
Short for Dynamic Link Library, a DLL is a library of executable functions or data that can be used by a Windows application. Typically, a DLL provides one or more particular functions and a program accesses the functions by creating either a static or dynamic link to the DLL. A static link remains constant during program execution while a dynamic link is created by the program as needed. DLLs can also contain just data. DLL files usually end with the extension .dll, .exe, .drv, or .fon. A DLL can be used by several applications at the same time. Some DLLs are provided with the Windows operating system and available for any Windows application. Other DLLs are written for a particular application and are loaded with the application.

Plug and Play
Plug and Play refers to the ability of a computer system to automatically configure expansion boards and other hardware devices. Devices can either be internal (sound cards, video adapter boards) or external (such as USB or Firewire drives, mouse or keyboards). Windows supports Plug and Play; when you attach a new hardware device to the computer and boot up, the operating system will detect the new hardware and install it, sometimes requiring some additional information about the device which must be given by the user.

Drivers
A driver is a program that controls a hardware device. Every device, whether it is a printer, disk drive or keyboard, must have a driver. Many drivers, such as the keyboard driver, come with the operating system. For other devices, you may need to load a new driver when you connect the device to your computer. A driver acts like a translator between the device and programs that use the device.

Drivers are installed once a device is connected to the computer. If it is a Plug and Play device, Windows will prompt for the driver, usually on a disk or CD. Updating a driver can be done by entering the Device Manager, selecting a device and clicking the Properties button: an Update Driver button will allow you to load new drivers. Windows will display a series of Wizards designed to walk you through the installation.

Hardware Conflicts
A hardware conflict is caused when one or more devices are misconfigured and thus inoperable. Conflicts are indicated in the Device Manager, usually recognizable by a yellow exclamation point or red X next to the misconfigured device.

Each device installed on a computer is assigned system resources, and sometimes two devices "fight" over them. These system resources include the following:

• IRQ
  Short for Interrupt Request Line, IRQs are hardware lines over which devices can send interrupt signals to the microprocessor. Windows will automatically assign an IRQ to a device if it is Plug and Play.
  
  
• I/O Address
  Short for Input/Output, each device must have its own I/O address to communicate with the processor.
  
  
• DMA Channels
  Short for Direct Memory Access, DMA channels allow for transferring data from main memory to a device without passing it through the CPU. A sound card will usually use two channels, but the rest of the channels can be used by other devices. A DMA conflict will not cause a system crash, but will slow down performance.
  
  
• Memory Address
  Some hardware devices contain a ROM chip with code which helps the device perform its functions. The computer has an area in memory specifically for ROM starting addresses, and a ROM address conflict will cause the system to freeze on startup.
  
  

Conflicts can usually be eliminated by removing the device in the Device Manager and allowing Windows to detect and reinstall it (after restarting the computer).

A Note about DOS
MS-DOS is a 16-bit operating system developed by Microsoft that was standard on IBM-compatible PCs before Windows came on the scene. Windows 3.1 was actually a GUI (Graphical User Interface) to DOS; DOS was the actual operating system. Newer versions of Windows have almost entirely left DOS behind, but the Win9x platform (including Windows ME) depends on DOS code to function. When troubleshooting Windows problems, you may have to boot in DOS mode, most notably when you are booting from a floppy to format a PC hard drive and reinstall Windows. For more information, please see:
Webopedia - DOS

Additional information and a useful DOS command reference are available at:
Information and help with Microsoft DOS