Problem wth System hardisk space

CASE:-

My 120 gig C drive partition yesterday reported 62.4 GB free. Today I get a warning telling me free space is dangerously low.
Checking it I see 53 mb free and checking it again 5 minutes later I see 26.7 mb free.System Restore is configured for 11% (13.21 GB). The other partition on this 250 gig drive is consistently reporting 69.4 GB free. 
When I do a restart I get totally different numbers for that C partition such a 43 GB free and something else again an hour later. 

Follow the steps in the following methods

Method 1 : 

Try running Disk clean up and check 

If you want to reduce the number of unnecessary files on your hard disk to free up disk space and help your computer run faster, use Disk Cleanup. It removes temporary files, empties the Recycle Bin, and removes a variety of system files and other items that you no longer need.

1. Open Disk Cleanup by clicking the Start button  , clicking All Programs , clicking Accessories , clicking System Tools , and then clicking Disk Cleanup .
2. In the Disk Cleanup Options dialog box, choose whether you want to clean up your own files only or all of the files on the computer.   If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
3. If the Disk Cleanup: Drive Selection dialog box appears, select the hard disk drive that you want to clean up, and then click OK .
4. Click the Disk Cleanup tab, and then select the check boxes for the files you want to delete.
5. When you finish selecting the files you want to delete, click OK , and then click Delete files to confirm the operation. Disk Cleanup proceeds to remove all unnecessary files from your computer.

The More Options tab is available when you choose to clean files from all users on the computer. This tab includes two additional ways to free even more disk space:

Method 2 : 

Improve performance by defragmenting your hard disk 

Fragmentation makes your hard disk do extra work that can slow down your computer. Disk Defragmenter rearranges fragmented data so your hard disk can work more efficiently. Disk Defragmenter runs on a schedule, but you can also defragment your hard disk manually.

1.    Open Disk Defragmenter by clicking the Start button  , clicking All Programs , clicking Accessories , clicking System Tools , and then clicking Disk Defragmenter .   If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

2.    Click Defragment Now .

Disk Defragmenter might take from several minutes to a few hours to finish, depending on the size and degree of fragmentation of your hard disk. You can still use your computer during the defragmentation process.

Method 3 :

Perform check disk on your computer.

1.    Click Start, click Run, type cmd, and then click OK. A Command Prompt window opens. 
2.    Type chkdsk /r, and then press ENTER.

You are prompted to schedule Chkdsk to run when the computer restarts. 
3.    Press Y, and then press ENTER. 
4.    Restart your computer. During startup, Windows will scan your disk for errors, and Windows will try to recover any files that are located on damaged areas on the disk.

you have some space you should install ncdu - ncurses disk usage
>> viewer. It shows you where all the space has gone and enables you to
>> navigate trough the directories. You can even delete files/dirs with it.

                                                                   MEMORY(Exclude Hardisk)

Internal storage areas in the computer The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.
Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.

Memory Manufacturers Corsair, Kingston, Rambus, Crucial, Samsung, PNY, Micron

Memory Terminology

Memory speed - measured in nanoseconds, this is the time to access data that is stored in memory
the lower the nanoseconds the faster the memory (2ns-80ns)

Parity - A simple error checking method use in memory correction

ECC-Error correction code use in memory correction for newer computers

Memory Banks - A socket where memory is installed Example 4 banks will have 8MB of memory each for a total of 32MB

There are several different types of memory:

240-pin DIMM----------------------------- DDR3 SDRAM

                               ROM

ROM or Read Only Memory, Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to. It is non-volatile which means once you turn off the computer the information is still there.

PROM, short for programmable read-only memory A PROM is a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM, PROM's retain their contents when the computer is turned off. The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM.

EPROM (erasable programmable read-only memory) is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased.

EEPROM- Acronym for electrically erasable programmable read-only memory. Pronounced double-ee-prom or e-e-prom, an EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM. EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased one byte at a time whereas flash memory allows data to be written or erased in blocks. This makes flash memory faster. 

                             RAM

RAM (Random Access Memory) is a temporary (Volatile) storage area utilized by the CPU. Before a program can be ran the program is loaded into the memory which allows the CPU direct access to the program.

2 Types of RAM

SRAM Short for static random access memory, and pronounced ess-ram. SRAM is a type of memory that is faster and more reliable than the more common DRAM (dynamic RAM). The term static is derived from the fact that it doesn't need to be refreshed like dynamic RAM.
SRAM is often used only as a memory cache usually found in the CPU (L1, L2 and L3 Cache)

DRAM stands for dynamic random access memory, a type of memory used in most personal computers.

Types of DRAM Packages and DRAM Memory

LAPTOP MEMORY

(72, 144, 200) SO-DIMM

SO-DIMM Short for Small Outline DIMM, a small version of a DIMM used commonly in notebook computers. 72 supports 32bit and 144 and 200 SO-DIMM pins supports a full 64-bit transfer.

(144, 172) Micro-DIMM

Micro-DIMM Short for Micro Dual Inline Memory Module, a competing memory used on laptops, mostly supports 144 and 172 pins.

SIMM Acronym for single in-line memory module, a small circuit board that can hold a group of memory chips. Typically, SIMM's holds up 8 (on Macintoshes) or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking. Unlike memory chips, SIMM's is measured in bytes rather than bits. SIMM's is easier to install than individual memory chips. A SIMM is either 30 or 72 pins.

30 pin SIMM (Usually FPM or EDO RAM)

FPM RAM Short for Fast Page Mode RAM, a type of Dynamic RAM (DRAM) that allows faster access to data in the same row or page. Page-mode memory works by eliminating the need for a row address if data is located in the row previously accessed. It is sometimes called page mode memory.

 

72 pin SIMM (EDO RAM)

EDO DRAM Short for Extended Data Output Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.

DIMM Short for dual in-line memory module, a small circuit board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMM's two at a time. With DIMM's, you can install memory one DIMM at a time. A DIMM contains 168 pins.

168 pin DIMM (SDRAM)

SDRAM Short for Synchronous DRAM, a new type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU's bus and is capable of running at 133 MHz, about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM . SDRAM is replacing EDO DRAM in many newer computers
SDRAM delivers data in high speed burst

184 pin DIMM (DDR-SDRAM)

DDR SDRAM Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle, effectively doubling the memory chip's data throughput. DDR-SDRAM is also called SDRAM II.

240 DIMM (DDR2-SDRAM)

DDR2-SDRAM Short for Double Data Rate Synchronous DRAM 2 is a type of DDR that supports
higher's speeds than it's predecessor DDR SDRAM

240 DIMM (DDR3-SDRAM)

DDR3-SDRAM Short for Double Data Rate Synchronous DRAM 3 is the newest type of DDR that supports
the fastest speed of all the SDRAM memory

184 pin RIMM (RDRAM)

RIMM Rambus Inline Memory Module, The memory module used with RDRAM chips. It is similar to a DIMM package but uses different pin settings. Rambus trademarked the term RIMM as an entire word. It is the term used for a module using Rambus technology. It is sometimes incorrectly used as an acronym for Rambus Inline Memory Module. A RIMM contains 184 or 232pins. Note must use all sockets in RIMM installation or use C_RIMM to terminate banks

232 pin RIMM (RDRAM)

RDRAM Short for Rambus DRAM, a type of memory (DRAM) developed by Rambus, Inc.
In 1997, Intel announced that it would license the Rambus technology for use on its future motherboards, thus making it the likely de facto standard for memory architectures.

SIMM and DIMM Sockets

SDRAM Chart

  168 DIMM (SDRAM)

 

Module Standard	Module Format	Chip Type	Clock Speed (MHz)	Cycles Per clock	Bus Speed	Bus Width (Bytes)	Transfer Rate (MB/s)
PC66	SDR DIMM	10ns	66	1	66	8	533
PC100	SDR DIMM	8ns	100	1	100	8	800
PC133	SDR DIMM	7ns	133	1	133	8	1,066

DDR SDRAM Chart

184 DIMM (DDR-SDRAM)

Module Standard	Module Format	Chip Type	Clock Speed (MHz)	Cycles Per clock	Bus Speed	Bus Width (Bytes)	Transfer Rate (MB/s)
PC1600	DDR DIMM	DDR200	100	2	200	8	1,600
PC2100	DDR DIMM	DDR266	133	2	266	8	2.133
PC2700	DDR DIMM	DDR333	166	2	333	8	2,667
PC3200	DDR DIMM	DDR400	200	2	400	8	3,200
PC4000	DDR DIMM	DDR500	250	2	500	8	4,000
PC4300	DDR DIMM	DDR533	266	2	533	8	4,266

DDR2 SDRAM Chart

240 DIMM (DDR2-SDRAM)

Module Standard	Module Format	Chip Type	Clock Speed (MHz)	Cycles Per clock	Bus Speed	Bus Width (Bytes)	Transfer Rate (MB/s)
PC2-3200	DDR2 DIMM	DDR2-400	200	2	400	8	3,200
PC2-4300	DDR2 DIMM	DDR2-533	266	2	533	8	4,266
PC2-5400	DDR2 DIMM	DDR2-667	333	2	667	8	5,333
PC2-6400	DDR2 DIMM	DDR2-800	400	2	800	8	6,400

240 DIMM (DDR3-SDRAM)

Module Standard	Module Format	Chip Type	Clock Speed (MHz)	Cycles Per clock	Bus Speed	Bus Width (Bytes)	Transfer Rate (MB/s)
PC3-6400	DDR3 DIMM	DDR3-800	400	2	800	8	6,400
PC3-8500	DDR3 DIMM	DDR3-1066	533	2	1,066	8	8,500
PC3-10600	DDR3 DIMM	DDR3-1333	667	2	1,334	8	10,670
PC3-12800	DDR3 DIMM	DDR3-1600	800	2	1,600	8	12,800

RDRAM Chart

232 RIMM (RDRAM)

Module Standard	Module Format	Chip Type	Clock Speed (MHz)	Cycles Per clock	Bus Speed	Bus Width (Bytes)	Transfer Rate (MB/s)
RIMM 1200	RIMM-16	PC600	300	2	600	2	1,200
RIMM 1400	RIMM-16	PC700	350	2	700	2	1,400
RIMM 1600	RIMM-16	PC800	400	2	800	2	1,600
RIMM 2100	RIMM-16	PC1066	533	2	1,066	2	2,133
RIMM 2400	RIMM-16	PC1200	600	2	1,200	2	2,400
RIMM 3200	RIMM-32	PC800	400	2	800	2	3,200
RIMM 4200	RIMM-32	PC1066	533	2	1,066	2	4,266
RIMM 4800	RIMM-32	PC1200	600	2	1,200	2	4,800

RAM Desktop Installation

SIMM – Single Inline Memory Module Installation (30 or 72 pin)

1. Place SIMM in a 45 degree angle, push it upright to lock with the corresponding notch on the sides
2. Must be installed in same pairs
3. Must populate first two slots of the SIMM sockets in order for it to work

DIMM – Dual Inline Memory Module Installation (168, 184 or 240 pin)

1. The first thing you do is open the plastic retaining clips on each side of slots you are going to use.
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. DIMM’s can be installed as a single pair (unless it states Dual Channel then you must install it in pairs)

RIMM – Rambus Inline Memory Module Installation (184 or 232 pin)

1. The first thing you do is open the plastic retaining clips on each side of slots you are going to use.
2. Align the cut-out on the module pin connector with the engaging pin on the slot
3. Holding the module upright press down both ends.
4. When the module is correctly seated, retaining clips should lock automatically.
5. Must populate all RIMM slots available
3. If not unpopulated slots must use CRIMM’s (Continuity Rambus Inline Memory Module)

Memory Troubleshooting

MEMORY (when installing use a ground strap because of ESD)
ESD (low and high humidity)
Mixed Memory usually equals fried memory
Parity Errors or ECC Errors (Memory correction errors)
SIMMS must be installed in pairs
RIMMS must be all installed in all slots or CRIMM's must be needed in unvacated RIMM slots
General Protection Fault (memory overwrite)
Not enough memory (computer is slow)
NMI -Non Maskable Interrupt will cause BSOD (Blue Screen of Death)
Multiple beeps when booting up check that memory is properly installed and working
No Video (Reseat memory)
Memory speeds set in BIOS/CMOS Setup
Virtual Memory (Page fault)
Chip Creep - Thermal expansion and contraction

 Special Thanks to Rambus, Cosair, PNY, Viking, American Megatrends, Centon, Samsung, Crucial and Micron

How to make a bootable self installing backup image

What I want to do is make a bootable backup image that will self install without windows in case of an operating system failure where windows is unavailable. I want to image my C drive and make it so I can boot from CDR or DVDR and have it format the drive and reinstall my backup identical to the original. A long time ago I saw this done with Symantec Ghost on a job I was on but have no idea how to accomplish the task myself.




solution:-


Ghost does this very well.You just need a Symantec Ghost boot disk or cd go to create a image from the disk on your dvd.It will ask you if you want to boot with system on the image created you just need a boot diskette or a boot created by Ghost wizard. If you install Ghost software onyuor pc there is a feature called LightsOut Restore—Restores your system with an on-disk software recovery environment—no bootable CD required.
All you need is buy the software.


                               This will not work if there is a HDD failure.

How to remove new folder exe or regsvr exe or autorun inf virus

I was surprised that my most reliable friend Avast, for the first time failed me in this war against viruses but then again avg and bitdiffender also failed against it. This virus is know popularly as regsvr.exe virus, or as new folder.exe virus and most people identify this one by seeing autorun.inf file on their pen drives, But trend micro identified it as WORM_DELF.FKZ. It is spreading mostly using pen drives as the medium.

Manual Process of removal

I prefer manual process simply because it gives me option to learn new things in the process.

So let’s start the process off reclaiming the turf that virus took over from us.

1. Cut The Supply Line
   1. Search for autorun.inf file. It is a read only file so you will have to change it to normal by right clicking the file , selecting the properties and un-check the read only option
   2. Open the file in notepad and delete everything and save the file.
   3. Now change the file status back to read only mode so that the virus could not get access again.
   4. 
   5. Click start->run and type msconfig and click ok
   6. Go to startup tab look for regsvr and uncheck the option click OK.
   7. Click on Exit without Restart, cause there are still few things we need to do before we can restart the PC.
   8. Now go to control panel -> scheduled tasks, and delete the At1 task listed their.
   2. Open The Gates Of Castle
      1. Click on start -> run and type gpedit.msc and click Ok.
      2. 
      3. If you are Windows XP Home Edition user you might not have gpedit.msc in that case download and install it from Windows XP Home Edition: gpedit.msc and then follow these steps.
         
      4. Go to users configuration->Administrative templates->system
      5. Find “prevent access to registry editing tools” and change the option to disable.
      6. 
      7. Once you do this you have registry access back.
   3. Launch The Attack At Heart Of Castle
      1. Click on start->run and type regedit and click ok
      2. Go to edit->find and start the search for regsvr.exe,
      3. 
      4. Delete all the occurrence of regsvr.exe; remember to take a backup before deleting. KEEP IN MIND regsvr32.exe is not to be deleted. Delete regsvr.exe occurrences only.
      5. At one ore two places you will find it after explorer.exe in theses cases only delete the regsvr.exe part and not the whole part. E.g. Shell = “Explorer.exe regsvr.exe” the just delete the regsvr.exe and leave the explorer.exe
   4. Seek And Destroy the enemy soldiers, no one should be left behind
      1. Click on start->search->for files and folders.
      2. Their click all files and folders
      3. Type “*.exe” as filename to search for
      4. Click on ‘when was it modified ‘ option and select the specify date option
      5. Type from date as 1/31/2008 and also type To date as 1/31/2008
      6. 
      7. Now hit search and wait for all the exe’s to show up.
      8. Once search is over select all the exe files and shift+delete the files, caution must be taken so that you don’t delete the legitimate exe file that you have installed on 31^st January.
      9. Also selecting lot of files together might make your computer unresponsive so delete them in small bunches.
      10. Also find and delete regsvr.exe, svchost .exe( notice an extra space between the svchost and .exe)
   5. Time For Celebrations
      1. Now do a cold reboot (ie press the reboot button instead) and you are done.
   I hope this information helps you win your own battle against this virus. Soon all antivirus programs will be able to automatically detect and clean this virus. Also i hope Avast finds a way to solve this issues.
   

Creating Bootable Vista / Windows 7 USB Flash Drive

This will walk through the steps to create a bootable USB flash drive for the purpose of installing a Vista or Windows 7 OS.  These instructions assume that you have a computer with Windows Vista installed on it.

Required:

• USB Flash Drive (4GB+)
• Microsoft OS Disk (Vista / Windows 7)
• A computer running Vista / Windows 7

Step 1: Format the Drive
The steps here are to use the command line to format the disk properly using the diskpart utility. [Be warned: this will erase everything on your drive. Be careful.]

1. Plug in your USB Flash Drive
2. Open a command prompt as administrator (Right click on Start > All Programs > Accessories > Command Prompt and select “Run as administrator”
3. Find the drive number of your USB Drive by typing the following into the Command Prompt window:
   diskpart
   list disk
   The number of your USB drive will listed. You’ll need this for the next step.  I’ll assume that the USB flash drive is disk 1.
4. Format the drive by typing the next instructions into the same window. Replace the number “1” with the number of your disk below.
   select disk 1
   clean
   create partition primary
   select partition 1
   active
   format fs=NTFS
   assign
   exit
   When that is done you’ll have a formatted USB flash drive ready to be made bootable.

Step 2: Make the Drive Bootable
Next we’ll use the bootsect utility that comes on the Vista or Windows 7 disk to make the flash drive bootable.  In the same command window that you were using in Step 1:

1. Insert your Windows Vista / 7 DVD into your drive.
2. Change directory to the DVD’s boot directory where bootsect lives:
   d:
   cd d:\boot
3. Use bootsect to set the USB as a bootable NTFS drive prepared for a Vista/7 image. I’m assuming that your USB flash drive has been labeled disk G:\ by the computer:
   bootsect /nt60 g:
4. You can now close the command prompt window, we’re done here.

Step 3: Copy the installation DVD to the USB drive
The easiest way is to use Windows explorer to copy all of the files on your DVD on to the formatted flash drive.  After you’ve copied all of the files the disk you are ready to go.
Step 4: Set your BIOS to boot from USB
This is where you’re on your own since every computer is different. Most BIOS’s allow you to hit a key at boot and select a boot option.

ANOTHER SHORT WAY IZ :-

How to Make a USB Pen Drive Bootable

The Guide is based on creating/getting a USB Pen Drive to boot on the DFI NF4 series mobo. The second part shows how to flash your bios from the pen drive.

Part 1

1. The easiest way to do this is with a floppy drive, if you don't have one, there is an alternative method at the bottom of the guide.
2. For XP users insert a blank floppy disc into the drive, open My Computer and right click on your floppy drive and choose "Format" from the popup.
3. Make sure the 'create a bootable system disk' option is checked. This will add the system files needed by the USB drive from the floppy. Click 'OK' to format the disk.



4. HP are constantly changing this utility, and as such the version you download might differ from the one in the guide HP Drive Key Boot Utility V2.1.8. Its intended obviously for HP usb drives but works fine with most other usb drives.
5. Plug in your USB drive and run the HP USB disk storage tool.
6. Ensure that the tool has found the correct drive in the "Device" box. Change the "File System" to "FAT". Check the "Create a DOS startup disk" option, and in the "using DOS system files located at:" window, enter "A:\" to point the program to your floppy disk or browse to it. Now click 'Start'. The program will create the necessary boot files on the USB drive.



7. Reboot your pc, when you see the post screen hit the Escape key, this will bring up a Boot Menu screen. Choose your USB drive from the list and hit Enter.



8. If all has went well you should have rebooted to the C:\ prompt. Congratulations you have just made a Bootable USB pen drive.

Alternative Method for users with no Floppy drives For users without a floppy drive download the XP Custom Boot disc HERE. This is a .exe file that contains all of the system files that you will need. Extract the files to a folder using Winimage etc. In Step 6. Point the HP USB utility to the folder containing the XP Custom Boot files.

Notes: Some USB pen drives do NOT work, mp3 type pen drives don't work or at least the ones i have tried do not, only a dedicated pen drive should be used. The Corsair Flash Voyager USB Pen Drive work perfect.


*****************

Part 2


How to flash your bios from USB pen

WARNING!!!!! Do Not Flash a Bios While Overclocked, always set Stock Settings before Flashing any bios.

If you have followed the guide above and have a working bootable USB pen drive then you can easily use it for say, flashing your bios....here's how.

1. Download the correct bios for your motherboard from www.DFI.com
2. Next extract your downloaded DFI Bios to a folder using WinRAR or similar, Copy the xxxxxxx.BIN, the AUTOEXEC.BAT file and AWDFLASH.EXE utility to your new Bootable USB drive.
3. Right click the AUTOEXEC.BAT file and choose Edit, add the following lines to the AUTOEXEC.BAT file, or open the AUTOEXEC.BAT file with any text editor (Notepad) and Edit/Add the the lines below.

@echo off
cls
@ECHO OFF
C:\AWDFLASH xxxxxxx.BIN /cks/sn/py/cc/cd/cp/ld/qi/WB/ch
echo "The version of BIOS was inaccurate,"
echo "Please remove the floppy, download the right one and re-flash."
@ECHO OFF


4. Where xxxxxxx.BIN = the name of your bios.Bin file. The prompt needs changed to C:\ from A:\ as above.
5. Save the AUTOEXEC.BAT and Close it.
6. Make sure your Bootable USB drive is inserted and Reboot your Pc.
7. Hit Escape key when the post screen comes up to enter the Boot Menu Screen.
8. Select your Bootable USB pen drive from options listed and hit Enter. The bios should flash automatically. Follow instructions when its finished flashing.
9. Restart your Pc and enter the bios and Load Optimized Defaults. F10 to save settings and exit.

Thats it, if all went well you should have flashed your bios successfully from a Bootable USB pen drive. Congratulations.

WHAT IS COMUTER AND ITS STRUCTURE





A programmable machine. The two principal characteristics of a computer are:

It responds to a specific set of instructions in a well-defined manner.

• It can execute a prerecorded list of instructions (a program).

Modern computers are electronic and digital. The actual machinery -- wires, transistors, and circuits -- is called hardware; the instructions and data are called software.

All general-purpose computers require the following hardware components:

memory : Enables a computer to store, at least temporarily, data and programs.

mass storage device : Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.

input device : Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.

output device : A display screen, printer, or other device that lets you see what the computer has accomplished.

central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions.

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

Computers can be generally classified by size and power as follows, though there is considerable overlap:

personal computer : A small, single-user computer based on a microprocessor. In addition to the microprocessor, a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.

workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.

minicomputer : A multi-user computer capable of supporting from 10 to hundreds of users simultaneously.

mainframe : A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.

supercomputer : An extremely fast computer that can perform hundreds of millions of instructions per second.