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The course begins by introducing the concept of digital electronics and the different number systems technicians will most
likely encounter in digital work. This is followed by the introduction to basic logic gates, the fundamental building
blocks in digital electronics. The course tackles combinational logic using logic gates and techniques to simplify logic
circuits such as Boolean algebra and Karnaugh maps. Application flip-flops........
Hardware (computer)
Hardware (computer), equipment involved in the function of a computer. Computer hardware consists
of the components that can be physically handled. The function of these components is typically divided into three main categories:
input, output, and storage. Components in these categories connect to microprocessors, specifically, the computer's central
processing unit (CPU), the electronic circuitry that provides the computational ability and control of the computer, via wires
or circuitry called a bus.
Software, on the other hand, is the set of instructions a computer uses to manipulate data, such
as a word-processing program or a video game. These programs are usually stored and transferred via the computer's hardware
to and from the CPU. Software also governs how the hardware is utilized; for example, how information is retrieved from a
storage device. The interaction between the input and output hardware is controlled by software called the Basic Input Output
System software (BIOS).
Although microprocessors are still technically considered to be hardware, portions of their function are
also associated with computer software. Since microprocessors have both hardware and software aspects they are therefore often
referred to as firmware.
Input hardware consists of external devices—that is, components outside of the computer's CPU—that
provide information and instructions to the computer. A light pen is a stylus with a light sensitive tip that is used to draw
directly on a computer's video screen or to select information on the screen by pressing a clip in the light pen or by pressing
the light pen against the surface of the screen. The pen contains light sensors that identify which portion of the screen
it is passed over. A mouse is a pointing device designed to be gripped by one hand. It has a detection device (usually a ball)
on the bottom that enables the user to control the motion of an on-screen pointer, or cursor, by moving the mouse on a flat
surface. As the device moves across the surface, the cursor moves across the screen. To select items or choose commands on
the screen, the user presses a button on the mouse. A joystick is a pointing device composed of a lever that moves in multiple
directions to navigate a cursor or other graphical object on a computer screen. A keyboard is a typewriter-like device that
allows the user to type in text and commands to the computer. Some keyboards have special function keys or integrated pointing
devices, such as a trackball or touch-sensitive regions that let the user's finger motions move an on-screen cursor.
An optical scanner uses light-sensing equipment to convert images such as a picture or text into
electronic signals that can be manipulated by a computer. For example, a photograph can be scanned into a computer and then
included in a text document created on that computer. The two most common scanner types are the flatbed scanner, which is
similar to an office photocopier, and the handheld scanner, which is passed manually across the image to be processed. A microphone
is a device for converting sound into signals that can then be stored, manipulated, and played back by the computer. A voice
recognition module is a device that converts spoken words into information that the computer can recognize and process.
A modem, which stands for modulator-demodulator, is a device that connects a computer
to a telephone line or cable television network and allows information to be transmitted to or received from another computer.
Each computer that sends or receives information must be connected to a modem. The digital signal sent from one computer is
converted by the modem into an analog signal, which is then transmitted by telephone lines or television cables to the receiving
modem, which converts the signal back into a digital signal that the receiving computer can understand.
Output hardware consists of external devices that transfer information from the computer's CPU to the
computer user. A video display, or screen, converts information generated by the computer into visual information. Displays
commonly take one of two forms: a video screen with a cathode ray tube (CRT) or a video screen with a liquid crystal display
(LCD). A CRT-based screen, or monitor, looks similar to a television set. Information from the CPU is displayed using a beam
of electrons that scans a phosphorescent surface that emits light and creates images. An LCD-based screen displays visual
information on a flatter and smaller screen than a CRT-based video monitor. LCDs are frequently used in laptop computers.
Printers take text and image from a computer and print them on paper. Dot-matrix printers use tiny
wires to impact upon an inked ribbon to form characters. Laser printers employ beams of light to draw images on a drum that
then picks up fine black particles called toner. The toner is fused to a page to produce an image. Inkjet printers fire droplets
of ink onto a page to form characters and pictures.
Course Outline:
- Number Systems and Binary Arithmetic
- Basic Logic Gates
- Combinational Logic,Boolean Algebra,and K Maps
- Flip-flops
- Registers
- Counters
- Decoders
- Multiplexers
- Semiconductor Memories
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11/09/08/Sun
Internet Basics
Reviewed by: Ferdie S. De los Santos
Sometime in the
mid 1960’s, during the Cold War, it became apparent that there was a need for a bombproof communications system. A concept
was devised to link computers together throughout the country. With such a system in place large sections of the country could
be nuked and messages could still get through.
In the beginning,
only government “think tanks” and a few universities were linked. Basically the Internet was an emergency military
communications system operated by the Department of Defense’s Advanced Research Project Agency
(ARPA). The whole operation was referred to as ARPANET.
In time, ARPANET
computers were installed at every university in the United States
that had defense related funding. Gradually, the Internet had gone from a military pipeline to a communications tool for scientists.
As more scholars came online, the administration of the system transferred from ARPA to the National
Science Foundation.
Years later, businesses
began using the Internet and the administrative responsibilities were once again transferred.
At this time no
one party “operates” the Internet, there are several entities that “oversee” the system and the protocols
that are involved.
The speed of the
Internet has changed the way people receive information. It combines the immediacy of broadcast with the in-depth coverage
of newspapers…making it a perfect source for news and weather information.
Internet usage
is at an all time high. Almost 100 million U.S.
adults are now going online every month, according to New York-based Mediamark Research. That’s half of American adults
and a 27 percent increase over 1999 in the number who surf the Web.
There also appears
to be a continuing gender shift in the number of American adults going online. In early 2000, Mediamark reported the milestone
that women for the first time ever accounted for half of the online adult population. Now 51 percent of U.S. surfers - some 50.6 million - are women.
How It Works
For the purpose of this example
let’s say that you want to send a file to a friend who lives on the opposite side of the country. You select the file
that you friend wants and you send it to him via email.
Transmission Control Protocol / Internet Protocol (TCP/IP) prepares the data to be sent and received. TCP/IP
ensures that a Macintosh network can exchange data with a Windows, or a Unix network, and vice-versa.
The file that
you are sending does not travel to your friends computer directly, or even in a single continuous stream. The file you are
sending gets broken up into separate data packets. The Internet Protocol side of TCP/IP labels each packet with the unique
Internet address, or IP address of your friends computer. Since these packets will travel separate routes, some arriving sooner
than others, the Transmission Control Protocol side of TCP/IP assigns a sequence number to each of packets. These sequence
numbers will tell the TCP/IP in your friends computer how to reassemble the packets once he receives them. Amazingly, the
complicated process of TCP/IP takes place in a matter of milliseconds.
The packets are then sent from one “router” to the next. Each
router reads the IP address of the packet and decides which path will be the fastest. Since the traffic on these paths is
constantly changing each packet may be sent a different way.
It is possible
to discover the paths between routers using a utility known as Traceroute. Using
your favorite search engine, type in “traceroute” to find different Web sites hosting it.
Also, check out
the Internet Traffic Report to find out how much global Internet traffic there is at this moment…and where the “bottlenecks” are. This information may not useful to you…but it’s interesting! The Internet
Traffic Report monitors the flow of data around the world. It then displays a value between zero and 100. Higher values indicate
faster and more reliable connections. This information may not useful to you…but it’s interesting!
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