Tips and Tricks

AD-AWARE

Cookies are generally benign and useful little bits of data on our hard drive But they begin to concern us if they monitor and report our surfing activities to third-party advertisers and our email box begins to fill with spam. Lavasoft's Ad-aware at http://www.lavasoftusa.com is a free utility that does a very good job in scanning memory, drives, and Registry for spyware modules. You can then easily remove them or leave them there if you believe they serve a useful purpose. If in doubt, the program provides backup of removed files that can be restored later if you wish.
You can open a menu by holding the Alt key and typing the first letter of the menu title.

For example, pressing Alt + E opens the Edit menu. You can also press either Alt or F10 to activate the menu bar, then use the right and left arrow keys to highlight a menu name, and press Enter to open the highlighted menu.
Shift while inserting CD - bypasses auto-run

Check your C:\Windows\Temp folder periodically for the remnants of any crashed windows programs.

Close all open applications before deleting any ~xyz.tmp files.
To select more than one file or folder, hold down CTRL while you click each item.
Selecting Multiple Files: Selecting multiple files in large icon view works differently from list view.

To extend a selection, click the first icon, and then hold down the Shift key while you click the last icon to be selected. To change an icon from selected to unselected, hold down the Ctrl key while you select the icon.

Copying and Moving Files:
Click with right mouse button on the file and choose Copy
or Cut. Move to the destination location and click right mouse button on selected folder and choose Paste.

Print Screen Function when the Print Screen key is press in Windows, the information is copied to your clipboard.

To print the information you must open Paint (or a similar program), paste the clipboard information and print the image.

If in doubt Right-Click.
If you drag a file and drop it onto the Start button, Win98 adds a shortcut to the top of the Start menu. But if you drag the file over the Start button and *don't* drop it, the Start menu will open and you can position the new shortcut exactly where you want it.

QUICK ROUTE TO ROOT DIRECTORY.

A fast way to display the root directory is: click on Start, Run, and type "\" without quotes in the Run line. Click OK.
WinFiles.com Tips and Tricks Windows Magazine Tips

CLEAN UP THE STARTUP
To keep programs to a minimum in your startup group:
Start > Run, typing "msconfig" (without the quotes) and clicking on the Startup tab. Then, uncheck everything you can spare except for Explorer and Systray, click ApplyOK and reboot. This should free up some valuable resources.

SYSTEM SETTINGS PRINT
Holding the ALT key, double clicking on the My Computer icon. Click the Device Manager tab in the Systems Properties box, then the print button and select either a report on the system summary or a longer report on all devices and the system summary, then OK to print.
SHORTCUT TO SHORTCUT. If you have several Windows open and can't quickly locate a shortcut on your desktop, click on START in the lower left corner of your screen, then RUN, and simply type a period in the space and click OK. A display of all your desktop icons is displayed.
A QUICK CHANGE. Without so much as moving your hand from the mouse, you can change the size of an open application with a double click anywhere on the title bar. A second double-click in the same location toggles the screen back to its original size.

PASSWORD PREDICAMENT.

If you assigned a password to access Windows and then you suffer a memory lapse, not to worry. Bypass Windows with F8 during startup and choose the Command Prompt Only option. At the prompt, go to the Windows directory with "cd\windows" (without the quotes)) Delete .pwl files with "del *.pwl" (again, without the quotes) and no password will be required on the next boot. A new password can be set if you wish at the StartSettingsControl PanelPasswords and click on Change Windows Password.

MOUSE LOCATOR.

Windows XP makes it easy to locate your cursor by touching the CTRL key. To enable the feature, go to StartControl Panel and click the Mouse icon. Select the Mouse Properties and Pointer Options tabs and check "Show location of pointer when I press the CTRL key".
KEYBOARD NAVIGATION. Try holding the ALT key down and pressing the left arrow key to go back, or the right arrow key to go forward.
Select Start-Run, type msinfo32, and press .

SLIM DOWN YOUR FONTS

The trick is to move-not remove the fonts, so you can easily get them back.
First, create a folder on your hard drive called Excess Fonts, and open that folder in Windows Explorer. Select Start-Run, and type fonts, and press to bring up your Fonts folder in another Explorer window. Select fonts to remove (double-click a font to see how it looks), but keep Arial, Courier, Courier New, Modern, MS Sans Serif, and MS Serif (these two may appear as “MS Reference”), Symbol, Tahoma, Times New Roman, and Wingdings.
When you move a font, bring along its bold and italic variations. Drag unwanted fonts to Excess Fonts folder. If you ever need one of them, open both folders again and drag the font back to Fonts.

QUICKER SHUTDOWN.

If your Windows XP doesn't shut down as fast as you'd like, one alternative might help. Right click a blank area on your desktop, click NewShortcut and in the Create Shortcut Wizard's Type the Location of the Item box, type the following exactly without quotes: "shutdown -s -t 0". Make sure there is a space before each hyphen and that is a numeric character at the end. Click Next and in the Type a Name for This Shortcut box, enter "shutdown" or some descriptive title and click Finish. You may now use that shortcut on your desktop for a fast shut down, made even faster of course if you don't have any programs running when you click on it.

Tips for your success
Technology Get fast Internet connection (cable or ADSL) and use Internet as a resource library.
Stay on top with new technology: subscribe to PC Magazine, Yahoo and on-line newsletters. Read free Computer Paper.
Keep upgrading your computer hardware and software.

Take a speed reading course: What Speed Reading teaches you to do is to keep going through a text without re-reading words, sentences and sections over and over. It is really a form of self-discipline. You can read fast and still understand and retain information.
Never go anywhere without a book. Time spent waiting in line or in the car or whatever can be study time.

Keep a tape recorder in the car to record ideas that flow when you can't write things down.
Find a quiet place to study and be a little selfish with your time. Learn to say no.
Use post-it notes as bookmarks. Simply put a word or two at the top to create your own reference index.

Kill your TV ! Don't waste time!
Be an active reader. Take notes. In your own books write in the margins. Highlight the most important parts Don't reread irrelevant stuff.
Find time to rest. getting totally exhausted hampers your learning efforts. Get adequate amount of sleep!

Exercise a bit. It stimulates blood flow to the brain and relieves tension.
Read all your work aloud to someone else. It'll save valuable time proof reading, and improve your writing. If it sounds crummy, it is.

Learn to recognize and manage your emotions - Feelings and behavior are just as important as facts and knowledge. It involves
self-awareness and self-control
motivation and persistence
empathy, and the ability to form mutually satisfying relationships - the ability to recognize personal feelings and emotions and those of others
the ability to use that information to resolve conflicts, solve problems, and improve interactions with others.

Strategies include approaching people positively instead of avoiding them, listening without judging, and giving feedback skillfully.

RAM

DRAM Dynamic random access memory. Comes in 80, 70, or 60 nanosecond (ns) speed. The lower the number, the faster the memory.
CDRAM Cached RAM (invented by Mitsubishi Electronics). It combines an SRAM cache with 4 or 16 MB of DRAM within a single chip. This onboard SRAM can be used as both a cache or a buffer and gives the RAM an approximate 15 ns access time.
EDRAM Enhanced DRAM (developed by Ramtron International Corp. of Colorado Springs). Like CDRAM also incorporates an on-chip SRAM cache.
EDO RAM Extended Data Out RAM is a form of DRAM that works by extending the time during which data can be read from memory. Provide from 4 to 15 per cent greater performance than standard DRAM.
RDRAM Rambus DRAM (Toshiba and Samsung). It's similar to SDRAM, but faster, says Rambus.
SRAM Static RAM. Is powered once and doesn't need to be continually refreshed, unlike dynamic RAM.
SDRAM Synchronous DRAM (from Texas Instruments) has its timing synchronized to the system clock. Is about 10 per cent faster than EDO RAM.
DDR Double Data Rate SDRAM
DDR basically doubles the rate of data transfer of standard SDRAM by transferring data on the up and down tick of a clock cycle. DDR memory operating at 333MHz actually operates at 166MHz * 2 (aka PC333 / PC2700) or 133MHz*2 (PC266 / PC2100). DDR is a 2.5 volt technology that uses 184 pins in its DIMMs. It is incompatible with SDRAM physically, but uses a similar parallel bus, making it easier to implement than RDRAM, which is a different technology.
Rambus DRAM (RDRAM)
Despite it's higher price, Intel has given RDRAM it's blessing for the consumer market, and it will be the sole choice of memory for Intel's Pentium 4. RDRAM is a serial memory technology that arrived in three flavors, PC600, PC700, and PC800. PC800 RDRAM has double the maximum throughput of old PC100 SDRAM, but a higher latency. RDRAM designs with multiple channels, such as those in Pentium 4 motherboards, are currently at the top of the heap in memory throughput, especially when paired with PC1066 RDRAM memory.
DIMMs vs. RIMMs DRAM comes in two major form factors: DIMMs and RIMMS.
DIMMs are 64-bit components, but if used in a motherboard with a dual-channel configuration (like with an Nvidia nForce chipset) you must pair them to get maximum performance. So far there aren't many DDR chipset that use dual-channels. Typically, if you want to add 512 MB of DIMM memory to your machine, you just pop in a 512 MB DIMM if you've got an available slot. DIMMs for SDRAM and DDR are different, and not physically compatible. SDRAM DIMMs have 168-pins and run at 3.3 volts, while DDR DIMMs have 184-pins and run at 2.5 volts.
RIMMs use only a 16-bit interface but run at higher speeds than DDR. To get maximum performance, Intel RDRAM chipsets require the use of RIMMs in pairs over a dual-channel 32-bit interface. You have to plan more when upgrading and purchasing RDRAM.

Video memory types:
SGRAM Synchronous graphics RAM is a form of DRAM for graphics controllers and printers. According to Fujitsu, produces data bandwidth up to five times that of standard DRAM.
VRAM Video RAM. Co-called "dual port" memory types that allow the graphics processor to read from memory and redraw the screen simultaneously.
WRAM Window RAM (developed by Samsung Electronics) is both faster (50 percent performance increase) and less expensive than VRAM.
Memory Types
RAM chips used to be sold as individual chips, but today several RAM chips are soldered together onto a plug-in board called a module. This RAM module is called a SIMM (Single In-line Memory Module). SIMMs come in three basic designs: an older design that has 30 connector pins, a newer design that has 72 connector pins, and the newest design that has 168 connector pins (also called SDRAM). Each computer is designed to use one or the other of these SIMM designs, but today most all computers use the 72 pin design.

SIMMs come in several difference speeds. The most common speed is called 70 nanoseconds (ns). The rule in RAM is the lower (or smaller) the nanosecond number, the faster the RAM will operate. Therefore, a 60 ns SIMM is faster than a 70 ns SIMM. The new SDRAM has a speed of 10ns, which is 6 times faster than the fastest 72 pin SIMMS. All Pentium II and most new Pentium computers incorporate SDRAM.

Several new memory technologies seek to close the gap between processor and RAM performance. The goal is to increase the chips’s speed and widen the bandwidth with which they communicate with the processor. The players include double data rate RAM, or DDRRAM (also known as SDRAM II), SLDRAM, Direct RDRAM (aka Direct Rambus) and Concurrent RDRAM (aka Concurrent Rambus). Of these, Direct Rambus, endorsed by Intel, offers the greatest speed improvements, moving the peak bandwidth from SDRAM’s 125MBps to an astounding 1.6GBps.
When you think about it, it's amazing how many different types of electronic memory you encounter in daily life. Many of them have become an integral part of our vocabulary:
RAM
ROM
Cache
Dynamic RAM
Static RAM
Flash memory
Memory sticks
Volatile memory
Virtual memory
Video memory
BIOS
SIMM
DIMM
EDO RAM
RAMBUS
DIP


Double Data Rate (DDR) SDRAM: DDR is rated by its speed or potential bandwidth
PCI1600/DDR200 - 1.6 Gbps throughput, 200 MHz bus)
PCI12100/DDR266 - 2.1 Gbps throughput, 266 MHz bus)
PCI2700/DDR333 - 2.7 Gbps throughput, 333 MHz bus)

buffer (To move data into a temporary storage area)

A temporary storage area, usually in RAM. The purpose of most buffers is to act as a holding area, enabling the CPU to manipulate data before transferring it to a device.

Because the processes of reading and writing data to a disk are relatively slow, many programs keep track of data changes in a buffer and then copy the buffer to a disk. For example, word processors employ a buffer to keep track of changes to files. Then when you save the file, the word processor updates the disk file with the contents of the buffer. This is much more efficient than accessing the file on the disk each time you make a change to the file.

Note that because your changes are initially stored in a buffer, not on the disk, all of them will be lost if the computer fails during an editing session. For this reason, it is a good idea to save your file periodically. Most word processors automatically save files at regular intervals.

Another common use of buffers is for printing documents. When you enter a PRINT command, the operating system copies your document to a print buffer (a free area in memory or on a disk) from which the printer can draw characters at its own pace. This frees the computer to perform other tasks while the printer is running in the background. Print buffering is called spooling.
cache

Pronounced cash, a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching.

A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.

Some memory caches are built into the architecture of microprocessors. The Intel 80486 microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache. Such internal caches are often called Level 1 (L1) caches. Most modern PCs also come with external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.

Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk (as well as adjacent sectors) is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications, because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a hard disk.

When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged by its hit rate. Many cache systems use a technique known as smart caching, in which the system can recognize certain types of frequently used data. The strategies for determining which information should be kept in the cache constitute some of the more interesting problems in computer science.

Monitors

pixels
VGA Video Graphics Array 640 x 480
SVGA Super VGA 800 x 600
XGA eXtended Graphics Array 1024 x 786
SXGA Super XGA 1280 x 1204
UXGA Ultra XGA 1600 x 1200
QXGA Quad XGA 2048 x1536
WXGA Wide XGA 1280 x 800
WSXGA+ Wide XGA plus 1680 x 1050
WUXGA Wide Ultra XGA 1920 x 1200

Calibrating Monitor Gamma

LCD/Flat panel Monitors
Short for liquid crystal display, LCD displays use two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light.

Keyboard shorcuts

HANDY KEYS. Before that Windows key (the one with the Windows logo in the lower left of the keyboard) gets rusty for lack of use, look at all the handy things it will do for you: By itself, it displays the Start menu. With D, it minimizes or restores all Windows, with E it displays the Wondows Explorer, with Tab it cycles through active applications on your taskbar, and with F it displays the find function for all files. Use it with F1 to display Help, with R to display the Run command, and with Pause/Break for the System Properties dialog window. With Shift + M, the Windows key will undo minimizing all Windows, and with Ctrl + F it will display the find: computer dialog window. All these work on at least Windows 98 and XP operating system and you can experiment on the others as you please.
MOUSE WHEEL REVISITED. That wheel on your mouse (if you have one) can be useful with Internet Explorer. With the Ctrl key depressed, moving the wheel forward or backward resizes the font. With the Shift key depressed, the wheel moves you backward or forward to other sites visited in the current browsing session.
You can open a menu by holding the Alt key and typing the first letter of the menu title. For example, pressing Alt + E opens the Edit menu. You can also press either Alt or F10 to activate the menu bar, then use the right and left arrow keys to highlight a menu name, and press Enter to open the highlighted menu.
WINDOW + M - Have you ever wanted to get to your Desktop screen fast, but found yourself closing applications with your mouse? Try this shortcut, which instantly minimizes all open windows and returns you to the desktop in one quick jump. (The WINDOW key is the one between CTRL and ALT.)
WINDOW + E - This lauches an instance of Windows Explorer, a very handy program for file management. Use this shortcut intead of running through the Start > Programs > Accessories > Windows Explorer route.
SHIFT + CTRL + ARROWS - This shortcut is very handy for selecting text in HTML or text editors. Rather than highlighting with a mouse, this will quickly grab text one word at a time from the cursor position.
Cut: Ctrl > X Copy: Ctrl > C Paste: Ctrl > V
Undo: Ctrl > Z Select All: Ctrl > A


F10 - goes to menu mode
Alt - activates menu Enter - opens Esc - Cancels
Ctrl > Tab or Ctrl > Shift > Tab (in Properties) - Switches between properties tabs

Alt > Space Bar - open application central box
Alt > Enter - switch from icons to editing mode
Alt > Tab - to switch between running programs
Alt > Enter - properties Ctrl > F4 - to close window
Alt > double-click - properties Ctrl > Esc - display start menu
Alt > F4 - to exit program Ctrl > End go to end of a document
Shift > F10 - context menu for selected item

F1 - Help F3 - Find
Ctrl > Shift + drag a file to the desktop or a folder to create a shortcut

CLOSING POPUPS AND AD BANNERS. Next time you're annoyed with a popup message or ad banner, try Ctrl+W to close it. This works with some browsers, some popups, and some ads, but not all. Still, it's worth a try.
INTERNET EXPLORER SHORTCUTS. Here's a few keyboard shortcuts you might find handy in Microsoft Internet Explorer versions 5.0 and 5.5. In combination with the CTRL key, O (alpha, not numeric) opens the Address box so you can enter a URL; I opens the Favorites list, H the History list, E the Search menu, F the Find box, and N a new browser window.

Fundamentals

OS Operating System (e.g. DOS, Windows 3.1, Windows 95, Windows 98, Windows NT, Novell NetWare, OS/2, SCO Unix, Banyan Vines, ..)
ROM Read-Only Memory
BIOS Basic Input Output System
CPU The microchip or Central Processing Unit
Byte and bits
Just as a word is made up of letters, a byte is made up of bits. While words have a variable number of letters, all bytes have eight bits. A bit represents a positive or negative electric charge. The computer interprets these electric states as either the digits 0 (negative charge) or 1 (positive charge). These are the only two digits the computer can understand. Because of this, computers work on a binary number system, instead of the decimal system we are used to. The word bit stands for binary digit.
The computer interprets the negative and positive electric charges as binary digits (bits), and groups eight bits together. The sequence of the eight 1s and 0s identifies one byte from another. There are 256 different possible 0-1 combinations the eight bits can make (2 to the power of 8 = 256), and so a computer can identify 256 different characters. This is a sufficient number to represent all of the uppercase and lowercase letters of the alphabet, the digits 0-9, all the punctuation marks, a symbol used by the computer for a space, special characters such a * and I, other symbols used specifically by the computer, and still leave plenty of possible symbols for future uses.
8 bits = 1 byte
1,024 bytes = 1 kilobyte (K)
1,024 kilobytes - 1 megabyte (MB)
1,024 megabytes = 1 gigabyte (GB)
1,024 gigabytes = 1 terabyte (TB)
kilo- k 1000^1 1024^1 = 2^10 = 1,024
mega- M 1000^2 1024^2 = 2^20 = 1,048,576
giga- G 1000^3 1024^3 = 2^30 = 1,073,741,824
tera- T 1000^4 1024^4 = 2^40 = 1,099,511,627,776
peta- 1000^5 1024^5 = 2^50 = 1,125,899,906,842,624
exa- 1000^6 1024^6 = 2^60 = 1,152,921,504,606,846,976
zetta- 1000^7 1024^7 = 2^70 = 1,180,591,620,717,411,303,424
yotta- 1000^8 1024^8 = 2^80 = 1,208,925,819,614,629,174,706,176
Name Abbr. Size
Kilo K 2^10 = 1,024
Mega M 2^20 = 1,048,576
Giga G 2^30 = 1,073,741,824
Tera T 2^40 = 1,099,511,627,776
Peta P 2^50 = 1,125,899,906,842,624
Exa E 2^60 = 1,152,921,504,606,846,976
Zetta Z 2^70 = 1,180,591,620,717,411,303,424
Yotta Y 2^80 = 1,208,925,819,614,629,174,706,176

Object Linking and Embedding (OLE)
If the object is embedded, then the illustration remains under control of the original application.
If the object is linked, changes you make through your application are made directly to the source file.
Every file format in the world Search for file extensions Computer Unit Converter
Peripherals are attach to your PC via ports:
Serial Port - 115 Kbps USB - 12 Mbps = 12 million bits per second
FireWire - IEEE 1394
- 400 Mbps USB 2.0- 480 Mbps
Peripheral Component Interconnect (PCI)
(PCI) A standard for connecting peripherals to a personal computer, designed by Intel and released around Autumn 1993. PCI is supported by most major manufacturers including Apple Computer. It is technically far superior to VESA's local bus. It runs at 20 - 33 MHz and carries 32 bits at a time over a 124-pin connector or 64 bits over a 188-pin connector. An address is sent in one cycle followed by one word of data (or several in burst mode).
Accelerated Graphics Port (AGP)
A bus specification by Intel which gives low-cost 3D graphics cards faster access to main memory on personal computers than the usual PCI bus.

AGP dynamically allocates the PC's normal RAM to store the screen image and to support texture mapping, z-buffering and alpha blending.

Intel has built AGP into a chipset for its Pentium II microprocessor AGP cards are slightly longer than a PCI card.

AGP operates at 66 MHz, doubled to 133 MHz, compared with PCI's 33 Mhz. AGP allows for efficient use of frame buffer memory, thereby helping 2D graphics performance as well.

AGP provides a coherent memory management design which allows scattered data in system memory to be read in rapid bursts.
PCI Express Architecture
PCI Express is the latest I/O interconnect technology that will replace the existing PCI. With a bus bandwidth 4 times higher than that of AGP 8X interface, PCI Express x16 bus performs much better than AGP 8X in applications such as 3D gaming. PCI Express x1 also outperforms PCI interface with its exceptional high bandwidth up to 500MB/s. The high speed PCI Express interface creates new usages on desktop PCs e.g., Gigabit LAN, 1394b, and high-speed RAID systems.
T E X T B I N A R Y
Text
Typically, the term text refers to text stored as ASCII codes (that is, without any formatting). Objects that are not text include graphics, numbers (if they're not stored as ASCII characters), and program code. Binary
1. A number representation consisting of 0's and 1's used by practically all computers because of its ease of implementation using digital electronics and Boolean algebra.

2. Any file format for digital data encoded as a sequence of bits but not consisting of a sequence of printable characters (text). The term is often used for executable machine code. Of course all digital data, including characters, is actually binary data (unless it uses some (rare) system with more than two discrete levels) but the distinction between binary and text is well established.

ASCII - American Standard Code for Information Interchange. This is the world-wide standard for the code numbers used by computers to represent all the upper and lower-case Latin letters, numbers, punctuation, etc. There are 128 standard ASCII codes each of which can be represented by a 7 digit binary number: 0000000 through 1111111.
EBCDIC - Extended Binary Coded Decimal Interchange Code Pronounced eb-see-dik, EBCDIC is an IBM code for representing characters as numbers. Although it is widely used on large IBM computers, most other computers, including PCs and Macintoshes, use ASCII codes. [/eb's*-dik/, /eb'see"dik/, or /eb"k*-dik/ ]
COMPUTER TERMINOLOGY

State-of-the-art Any computer you can't afford
Obsolete Any computer you own
Microsecond The time it takes for your state-of-the-art computer to become obsolete
Keyboard The standard way to generate computer errors
Mouse An advanced input device to make computer errors easier to generate
Floppy The state of your wallet after purchasing a computer
Portable Computer A device invented to force businessmen to work at home, on vacation, and on business trips
Disk Crash A typical computer response to any critical deadline
Power User Anyone who can format a disk from DOS
System Update A quick method of trashing ALL of your software

About CPU and executing programs

A COMPUTER IS A COMPLEX SYSTEM consisting of many different components. But at the heart -- or the brain, if you want -- of the computer is a single component that does the actual computing. This is the Central Processing Unit, or CPU. In a modern desktop computer, the CPU is a single "chip" on the order of one square inch in size. The job of the CPU is to execute programs.

A program is simply a list of unambiguous instructions meant to be followed mechanically by a computer. A computer is built to carry out instructions that are written in a very simple type of language called machine language. Each type of computer has its own machine language, and it can directly execute a program only if it is expressed in that language. (It can execute programs written in other languages if they are first translated into machine language.)

When the CPU executes a program, that program is stored in the computer's main memory (also called the RAM or random access memory). In addition to the program, memory can also hold data that is being used or processed by the program. Main memory consists of a sequence of locations. These locations are numbered, and the sequence number of a location is called its address. An address provides a way of picking out one particular piece of information from among the millions stored in memory. When the CPU needs to access the program instruction or data in a particular location, it sends the address of that information as a signal to the memory; the memory responds by sending back the data contained in the specified location. The CPU can also store information in memory by specifying the information to be stored and the address of the location where it is to be stored.


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Microprocessor History
A microprocessor -- also known as a CPU or central processing unit -- is a complete computation engine that is fabricated on a single chip. The first microprocessor was the Intel 4004, introduced in 1971. The 4004 was not very powerful -- all it could do was add and subtract, and it could only do that 4 bits at a time. But it was amazing that everything was on one chip. Prior to the 4004, engineers built computers either from collections of chips or from discrete components (transistors wired one at a time). The 4004 powered one of the first portable electronic calculators.

The first microprocessor to make it into a home computer was the Intel 8080, a complete 8-bit computer on one chip, introduced in 1974. The first microprocessor to make a real splash in the market was the Intel 8088, introduced in 1979 and incorporated into the IBM PC (which first appeared around 1982). If you are familiar with the PC market and its history, you know that the PC market moved from the 8088 to the 80286 to the 80386 to the 80486 to the Pentium to the Pentium II to the Pentium III to the Pentium 4. All of these microprocessors are made by Intel and all of them are improvements on the basic design of the 8088. The Pentium 4 can execute any piece of code that ran on the original 8088, but it does it about 5,000 times faster!

The following table helps you to understand the differences between the different processors that Intel has introduced over the years.

Name Date Transistors Microns Clock speed Data width
8080 1974 6,000 6 2 MHz 8 bits
8088 1979 29,000 3 5 MHz 16 bits, 8-bit bus
80286 1982 134,000 1.5 6 MHz 16 bits
80386 1985 275,000 1.5 16 MHz 32 bits
80486 1989 1,200,000 1 25 MHz 32 bits
Pentium 1993 3,100,000 0.8 60 MHz 32 bits, 64-bit bus
Pentium II 1997 7,500,000 0.35 233 MHz 32 bits, 64-bit bus
Pentium III 1999 9,500,000 0.25 450 MHz 32 bits, 64-bit bus
Pentium 4 2000 42,000,000 0.18 1.5 GHz 32 bits, 64-bit bus

Part 2: Polling Loops and Interrupts

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THE CPU SPENDS ALMOST ALL ITS TIME fetching instructions from memory and executing them. However, the CPU and main memory are only two out of many components in a real computer system. A complete system contains other devices such as:

A hard disk for storing programs and data files. (Note that main memory holds only a comparatively small amount of information, and holds it only as long as the power is turned on. A hard disk is necessary for permanent storage of larger amounts of information, but programs have to be loaded from disk into main memory before they can actually be executed.)
A keyboard and mouse for user input.
A monitor and printer which can be used to display the computer's output.
A network interface that allows the computer to communicate with other computers that are connected to it on a network.
A scanner that converts images into coded binary numbers that can be stored and manipulated on the computer.
The list of devices is entirely open ended, and computer systems are built so that they can easily be expanded by adding new devices. Somehow the CPU has to communicate with and control all these devices. The CPU can only do this by executing machine language instructions (which is all it can do, period). So, for each device in a system, there is a device driver, which consists of software that the CPU executes when it has to deal with the device. Installing a new device on a system generally has two steps: plugging the device physically into the computer, and installing the device driver software. Without the device driver, the actual physical device would be useless, since the CPU would not be able to communicate with it.


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A computer system consisting of many devices is typically organized by connecting those devices to one or more busses. A bus is a set of wires that carry various sorts of information between the devices connected to those wires. The wires carry data, addresses, and control signals. An address directs the data to a particular device and perhaps to a particular register or location within that device. Control signals can be used, for example, by one device to alert another that data is available for it on the data bus. A fairly simple computer system might be organized like this:



Now, devices such as keyboard, mouse, and network interface can produce input that needs to be processed by the CPU. How does the CPU know that the data is there? One simple idea, which turns out to be not very satisfactory, is for the CPU to keep checking for incoming data over and over. Whenever it finds data, it processes it. This method is called polling, since the CPU polls the input devices continually to see whether they have any input data to report. Unfortunately, although polling is very simple, it is also very inefficient. The CPU can waste an awful lot of time just waiting for input.

To avoid this inefficiency, interrupts are often used instead of polling. An interrupt is a signal sent by another device to the CPU. The CPU responds to an interrupt signal by putting aside whatever it is doing in order to respond to the interrupt. Once it has handled the interrupt, it returns to what it was doing before the interrupt occurred. For example, when you press a key on your computer keyboard, a keyboard interrupt is sent to the CPU. The CPU responds to this signal by interrupting what is doing, reading the key that you pressed, processing it, and then returning to the task it was performing before you pressed the key.

Again, you should understand that this is purely mechanical process: A device signals an interrupt simply by turning on a wire. The CPU is built so that when that wire is turned on, it saves enough information about what it is currently doing so that it can return to the same state later. This information consists of the contents of important internal registers such as the program counter. Then the CPU jumps to some predetermined memory location and begins executing the instructions stored there. Those instructions make up an interrupt handler that does the processing necessary to respond to the interrupt. (This interrupt handler is part of the device driver software for the device that signalled the interrupt.) At the end of the interrupt handler is an instruction that tells the CPU to jump back to what it was doing; it does that by restoring its previously saved state.

Interrupts allow the CPU to deal with asynchronous events. In the regular fetch-and-execute cycle, things happen in a predetermined order; everything that happens is "synchronized" with everything else. Interrupts make it possible for the CPU to deal efficiently with events that happen "asynchronously", that is, at unpredictable times.

As another example of how interrupts are used, consider what happens when the CPU needs to access data that is stored on the hard disk. The CPU can only access data directly if it is in main memory. Data on the disk has to be copied into memory before it can be accessed. Unfortunately, on the scale of speed at which the CPU operates, the disk drive is extremely slow. When the CPU needs data from the disk, it sends a signal to the disk drive telling it to locate the data and get it ready. (This signal is sent synchronously, under the control of a regular program.) Then, instead of just waiting the long and unpredicatalble amount of time the disk drive will take to do this, the CPU goes on with some other task. When the disk drive has the data ready, it sends an interrupt signal to the CPU. The interrupt handler can then read the requested data.


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All modern computers use multitasking to perform several tasks at once. Some computers can be used by several people at once. Since the CPU is so fast, it can quickly switch its attention from one user to another, devoting a fraction of a second to each user in turn. This application of multitasking is called timesharing. But even modern personal computers with a single user use multitasking. For example, the user might be typing a paper while a clock is continuously displaying the time and a file is being downloaded over the network.

Each of the individual tasks that the CPU is working on is called a thread. (Or a process; there are technical differences between threads and processes, but they are not important here.) At any given time, only one thread can actually be executed by a CPU. The CPU will continue running the same thread until one of several things happens:

The thread might voluntarily yield control, to give other threads a chance to run.
The thread might have to wait for some asynchronous event to occur. For example, the thread might request some data from the disk drive, or it might wait for the user to press a key. While it is waiting, the thread is said to be blocked, and other threads have a chance to run. When the event occurs, an interrupt will "wake up" the thread so that it can continue running.
The thread might use up its alloted slice of time and be suspended to allow other threads to run. Not all computers can "forcibly" suspend a thread in this way; those that can are said to use preemptive multitasking. To do preemptive multitasking, a computer needs a special timer device that generates an interrupt at regular intervals, such as 100 times per second. When a timer interrupt occurs, the CPU has a chance to switch from one thread to another, whether the thread that is currently running likes it or not.
Ordinary users, and indeed ordinary programmers, have no need to deal with interrupts and interrupt handlers. They can concentrate on the different tasks or threads that they want the computer to perform; the details of how the computer manages to get all those tasks done are not relevant to them. In fact, most users, and many programmers, can ignore threads and multitasking altogether. However, threads have become increasingly important as computers have become more powerful and as they have begun to make more use of multitasking. Indeed, threads are built into the Java programming language as a fundamental programming concept.

Just as important in Java and in modern programming in general is the basic concept of asynchronous events. While programmers don't actually deal with interrupts directly, they do often find themselves writing event handlers, which, like interrupt handlers, are called asynchronously when specified events occur. Such "event-driven programming" has a very different feel from the more traditional straight-though, synchronous programming.


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By the way, the software that does all the interrupt handling and the communication with the user and with hardware devices is called the operating system. The operating system is the basic, essential software without which a computer would not be able to function. Other programs, such as word processors and World Wide Web browsers, are dependent upon the operating system. Common operating systems include UNIX, DOS, Windows, and the Macintosh OS.

D i c t i o n a r y
MMX - Matrix Math eXtensions
A set of 57 extra instructions built into some versions of Intel's Pentium microprocessors for supporting SIMD operations on multimedia and communications data types.
Single Instruction/Multiple Data
The classification under Flynn's taxonomy for a parallel processor where many processing elements (functional units) perform the same operations on different data. There is often a central controller which broadcasts the instruction stream to all the processing elements.
floating-point
In essence, computers are integer machines and are capable of representing real numbers only by using complex codes. The most popular code for representing real numbers is called the IEEE Floating-Point Standard .
Because mathematics with floating-point numbers requires a great deal of computing power, many microprocessors come with a chip, called a floating point unit (FPU ), specialized for performing floating-point arithmetic. FPUs are also called math coprocessors and numeric coprocessors.
transistor
A device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in 1947 at Bell Labs, transistors have become the key ingredient of all digital circuits, including computers. Today's microprocessors contains tens of millions of microscopic transistors.
L2 cache
Short for Level 2 cache, cache memory that is external to the microprocessor. In general, L2 cache memory, also called the secondary cache, resides on a separate chip from the microprocessor chip. Although, more and more microprocessors are including L2 caches into their architectures.
frontside bus
The bus within a microprocessor that connects the CPU with main memory. It's used to communicate between the motherboard and other components in a computer system.

Bits and Bytes

Bits and Bytes
If you have used a computer for more than five minutes, then you have heard the words bits and bytes. Both RAM and hard disk capacities are measured in bytes, as are file sizes when you examine them in a file viewer.
You might hear an advertisement that says, "This computer has a 32-bit Pentium processor with 64 megabytes of RAM and 2.1 gigabytes of hard disk space."

Decimal Numbers
The easiest way to understand bits is to compare them to something you know: digits. A digit is a single place that can hold numerical values between 0 and 9. Digits are normally combined together in groups to create larger numbers. For example, 6,357 has four digits. It is understood that in the number 6,357, the 7 is filling the "1s place," while the 5 is filling the 10s place, the 3 is filling the 100s place and the 6 is filling the 1,000s place. So you could express things this way if you wanted to be explicit:


(6 * 1000) + (3 * 100) + (5 * 10) + (7 * 1) = 6000 + 300 + 50 + 7 = 6357
Another way to express it would be to use powers of 10. Assuming that we are going to represent the concept of "raised to the power of" with the "^" symbol (so "10 squared" is written as "10^2"), another way to express it is like this:


(6 * 10^3) + (3 * 10^2) + (5 * 10^1) + (7 * 10^0) = 6000 + 300 + 50 + 7 = 6357
What you can see from this expression is that each digit is a placeholder for the next higher power of 10, starting in the first digit with 10 raised to the power of zero.

That should all feel pretty comfortable -- we work with decimal digits every day. The neat thing about number systems is that there is nothing that forces you to have 10 different values in a digit. Our base-10 number system likely grew up because we have 10 fingers, but if we happened to evolve to have eight fingers instead, we would probably have a base-8 number system. You can have base-anything number systems. In fact, there are lots of good reasons to use different bases in different situations.

Bits
Computers happen to operate using the base-2 number system, also known as the binary number system (just like the base-10 number system is known as the decimal number system). The reason computers use the base-2 system is because it makes it a lot easier to implement them with current electronic technology. You could wire up and build computers that operate in base-10, but they would be fiendishly expensive right now. On the other hand, base-2 computers are relatively cheap.

So computers use binary numbers, and therefore use binary digits in place of decimal digits. The word bit is a shortening of the words "Binary digIT." Whereas decimal digits have 10 possible values ranging from 0 to 9, bits have only two possible values: 0 and 1. Therefore, a binary number is composed of only 0s and 1s, like this: 1011. How do you figure out what the value of the binary number 1011 is? You do it in the same way we did it above for 6357, but you use a base of 2 instead of a base of 10. So:


(1 * 2^3) + (0 * 2^2) + (1 * 2^1) + (1 * 2^0) = 8 + 0 + 2 + 1 = 11
You can see that in binary numbers, each bit holds the value of increasing powers of 2. That makes counting in binary pretty easy. Starting at zero and going through 20, counting in decimal and binary looks like this:

0 = 0
1 = 1
2 = 10
3 = 11
4 = 100
5 = 101
6 = 110
7 = 111
8 = 1000
9 = 1001
10 = 1010
11 = 1011
12 = 1100
13 = 1101
14 = 1110
15 = 1111
16 = 10000
17 = 10001
18 = 10010
19 = 10011
20 = 10100
When you look at this sequence, 0 and 1 are the same for decimal and binary number systems. At the number 2, you see carrying first take place in the binary system. If a bit is 1, and you add 1 to it, the bit becomes 0 and the next bit becomes 1. In the transition from 15 to 16 this effect roles over through 4 bits, turning 1111 into 10000.


Bytes
Bits are rarely seen alone in computers. They are almost always bundled together into 8-bit collections, and these collections are called bytes. Why are there 8 bits in a byte? A similar question is, "Why are there 12 eggs in a dozen?" The 8-bit byte is something that people settled on through trial and error over the past 50 years.

With 8 bits in a byte, you can represent 256 values ranging from 0 to 255, as shown here:

0 = 00000000
1 = 00000001
2 = 00000010
...
254 = 11111110
255 = 11111111
In the article How CDs Work, you learn that a CD uses 2 bytes, or 16 bits, per sample. That gives each sample a range from 0 to 65,535, like this:
0 = 0000000000000000
1 = 0000000000000001
2 = 0000000000000010
...
65534 = 1111111111111110
65535 = 1111111111111111
Bytes are frequently used to hold individual characters in a text document. In the ASCII character set, each binary value between 0 and 127 is given a specific character. Most computers extend the ASCII character set to use the full range of 256 characters available in a byte. The upper 128 characters handle special things like accented characters from common foreign languages.

You can see the 127 standard ASCII codes below. Computers store text documents, both on disk and in memory, using these codes. For example, if you use Notepad in Windows 95/98 to create a text file containing the words, "Four score and seven years ago," Notepad would use 1 byte of memory per character (including 1 byte for each space character between the words -- ASCII character 32). When Notepad stores the sentence in a file on disk, the file will also contain 1 byte per character and per space.

Try this experiment: Open up a new file in Notepad and insert the sentence, "Four score and seven years ago" in it. Save the file to disk under the name getty.txt. Then use the explorer and look at the size of the file. You will find that the file has a size of 30 bytes on disk: 1 byte for each character. If you add another word to the end of the sentence and re-save it, the file size will jump to the appropriate number of bytes. Each character consumes a byte.

If you were to look at the file as a computer looks at it, you would find that each byte contains not a letter but a number -- the number is the ASCII code corresponding to the character (see below). So on disk, the numbers for the file look like this:

F o u r a n d s e v e n
70 111 117 114 32 97 110 100 32 115 101 118 101 110
By looking in the ASCII table, you can see a one-to-one correspondence between each character and the ASCII code used. Note the use of 32 for a space -- 32 is the ASCII code for a space. We could expand these decimal numbers out to binary numbers (so 32 = 00100000) if we wanted to be technically correct -- that is how the computer really deals with things.
Standard ASCII Character Set
The first 32 values (0 through 31) are codes for things like carriage return and line feed. The space character is the 33rd value, followed by punctuation, digits, uppercase characters and lowercase characters. 0 NUL
1 SOH
2 STX
3 ETX
4 EOT
5 ENQ
6 ACK
7 BEL
8 BS
9 TAB
10 LF 11 VT
12 FF
13 CR
14 SO
15 SI
16 DLE
17 DC1
18 DC2
19 DC3
20 DC4 21 NAK
22 SYN
23 ETB
24 CAN
25 EM
26 SUB
27 ESC
28 FS
29 GS
30 RS 31 US
32
33 !
34 "
35 #
36 $
37 %
38 &
39 '
40 ( 41 )
42 *
43 +
44 ,
45 -
46 .
47 /
48 0
49 1
50 2 51 3
52 4
53 5
54 6
55 7
56 8
57 9
58 :
59 ;
60 < 61 =
62 >
63 ?
64 @
65 A
66 B
67 C
68 D
69 E
70 F 71 G
72 H
73 I
74 J
75 K
76 L
77 M
78 N
79 O
80 P 81 Q
82 R
83 S
84 T
85 U
86 V
87 W
88 X
89 Y
90 Z 91 [
92 \
93 ]
94 ^
95 _
96 `
97 a
98 b
99 c
100 d 101 e
102 f
103 g
104 h
105 i
106 j
107 k
108 l
109 m
110 n 111 o
112 p
113 q
114 r
115 s
116 t
117 u
118 v
119 w
120 x 121 y
122 z
123 {
124 |
125 }
126 ~
127 DEL



Lots of Bytes
When you start talking about lots of bytes, you get into prefixes like kilo, mega and giga, as in kilobyte, megabyte and gigabyte (also shortened to K, M and G, as in Kbytes, Mbytes and Gbytes or KB, MB and GB). The following table shows the multipliers:

Name Abbr. Size
Kilo K 2^10 = 1,024
Mega M 2^20 = 1,048,576
Giga G 2^30 = 1,073,741,824
Tera T 2^40 = 1,099,511,627,776
Peta P 2^50 = 1,125,899,906,842,624
Exa E 2^60 = 1,152,921,504,606,846,976
Zetta Z 2^70 = 1,180,591,620,717,411,303,424
Yotta Y 2^80 = 1,208,925,819,614,629,174,706,176


You can see in this chart that kilo is about a thousand, mega is about a million, giga is about a billion, and so on. So when someone says, "This computer has a 2 gig hard drive," what he or she means is that the hard drive stores 2 gigabytes, or approximately 2 billion bytes, or exactly 2,147,483,648 bytes. How could you possibly need 2 gigabytes of space? When you consider that one CD holds 650 megabytes, you can see that just three CDs worth of data will fill the whole thing! Terabyte databases are fairly common these days, and there are probably a few petabyte databases floating around the Pentagon by now.


Binary Math
Binary math works just like decimal math, except that the value of each bit can be only 0 or 1. To get a feel for binary math, let's start with decimal addition and see how it works. Assume that we want to add 452 and 751:

452
+ 751
---
1203
To add these two numbers together, you start at the right: 2 + 1 = 3. No problem. Next, 5 + 5 = 10, so you save the zero and carry the 1 over to the next place. Next, 4 + 7 + 1 (because of the carry) = 12, so you save the 2 and carry the 1. Finally, 0 + 0 + 1 = 1. So the answer is 1203.
Binary addition works exactly the same way:

010
+ 111
---
1001
Starting at the right, 0 + 1 = 1 for the first digit. No carrying there. You've got 1 + 1 = 10 for the second digit, so save the 0 and carry the 1. For the third digit, 0 + 1 + 1 = 10, so save the zero and carry the 1. For the last digit, 0 + 0 + 1 = 1. So the answer is 1001. If you translate everything over to decimal you can see it is correct: 2 + 7 = 9.

Quick Recap

Bits are binary digits. A bit can hold the value 0 or 1.
Bytes are made up of 8 bits each.
Binary math works just like decimal math, but each bit can have a value of only 0 or 1.
There really is nothing more to it -- bits and bytes are that simple!

Dos Command

What are some examples of common DOS commands?

Note: replace the drive letter as needed for your own computer. Also, you can type these commands in either upper or lower case letters, because DOS does not distinguish case.
help list commands (only in DOS versions 5 or later)
help command get help on the DOS command "command"
command /? list switches for the DOS command "command"
path=c:\windows;c:\dos specify in which directories DOS searches for commands or programs
prompt $p$g make the DOS prompt display the current directory
dir list files in the current directory in one column
dir /w list files in five columns
dir /p list files one page at a time
dir *.exe list all files with an "EXE" extension
dir z???.exe list "EXE" files that have four letters and start with z
dir winsock.dll /s searches for the file "winsock.dll" in the current directory
type file.ext view the contents of the text file "file.ext"
edit file.ext use the DOS 5 editor to edit the file "file.ext"
a: change to the A: drive
md c:\myfiles make a new subdirectory named "myfiles"
cd c:\myfiles change to subdirectory "myfiles"
rd c:\myfiles remove the existing subdirectory named "myfiles"
del file.ext delete a file named "file.ext"
ren f1 f2 rename file "f1" to "f2"
copy f1 f2 copy file "f1" to "f2"
verify on turn on verification of copy commands
verify off turn off verification of copy commands
xcopy d1 d2 /s copy all files and subdirectories in directory "d1"
xcopy d1 d2 /p ask for confirmation of each file before copying
diskcopy a: b: duplicate a disk using two floppy drives
diskcopy a: a: duplicate a disk using the same floppy drive
format a: format a floppy disk in drive a:
format a: /s: format a bootable floppy disk (include system)
backup c:\d1\*.txt a: back up all files with the extension ".TXT" in "c:\d1\" to the "a:" floppy drive
backup c:\ a: /s back up the entire C: drive to floppy drive a:
restore a: c:\d1\*.txt restore certain files to C: from A:
restore a: c:\ /s restore backed-up files and subdirectories
ver check the version of DOS
time check or correct the system time
date check or correct the system date
cls clear the screen
scandisk scans and checks disk C for errors
chkdsk check disk and memory usage of the current disk
chkdsk /f fix errors reported by chkdsk
chkdsk filename check a particular file
chkdsk a: check a particular disk (a floppy in the a: drive)
mem check memory usage