aIr ROckETs?????

Flying model rockets is a relatively safe and inexpensive way for students to learn the basics of forces and the response of a vehicle to external forces. A model rocket is subjected to four forces in flight; weight, thrust, and the aerodynamic forces, lift and drag. There are many different types of model rockets. The first and simplest type of rocket that a student encounters is the compressed air, or stomp rocket. The air rocket system consists of two main parts, the launcher and the rocket.
On the figure we show a generic launcher, although launchers come in a wide variety of shapes and sizes. The launcher has a base to support the rocket during launch. A hollow launch tube is mounted perpendicular to the base and is inserted into the base of the rocket before launch. The launch tube is connected to an air pump by a hollow feeder line. The pump is used to pressurize the inside of the body tube to provide thrust for the rocket. We have attached a pressure gage to the feeder line to display the change in pressure in the system. For many air rockets, the pump is simply a cylinder which can be collapsed by striking with your hand or foot, which is where the "stomp" rocket got its name. In our simulation, we are going to pump up the system, and then launch the rocket, to better control and explain how the system works.
The other part of the compressed air rocket system is the rocket itself. The rocket has a hollow body tube which is opened on one end and closed at the other end by the nose cone. The body tube is only slightly larger than the launch tube. When the rocket is placed on the launch tube, the body tube becomes a closed pressure vessel. The pressure inside the body tube equals the pressure produced by the air pump. Fins are attached to the bottom of the body tube to provide stability during the flight.
The flight of a compressed air rocket is similar to the flight of a ballistic shell or a bullet fired from a gun. Unlike a model rocket, bottle rocket, or full scale rocket for which the thrust force is applied to the rocket for a large portion of the flight, the thrust of a stomp rocket is completely expended in the first instance of flight. During the entire flight, only the weight and aerodynamic forces act on the rocket.
The launch of a compressed air rocket proceeds in three stages; the pressurization of the body tube, the initial acceleration along the launch tube, and the expulsion of the compressed air from the rear of the rocket. Here is a computer animation of the launch of a compressed air rocket:

jeNAyAH SiBer!!!!

Kemunculan Internet sebagai alat komunikasi terkini menjanjikan satu wadah penyebaran maklumat yang memantapkan ilmu dan maklumat. Oleh kerana tiada siapa yang dapat mengawal perjalanan maklumat di dunia siber, berjuta-juta laman web telah dihidupkan. Bermacam-macam maklumat (sama ada benar atau salah), idea, ideologi, propaganda dan tidak kurang juga pornografi disebarkan melalui Internet.
Pada masa yang sama, kebebasan maklumat yang dijanjikan oleh dunia siber ini menimbulkan rasa gerun bagi pihak pentadbir sesetengah negara yang selama ini mahu mengongkong kebebasan bersuara, berfikir dan berpendapat penduduk mereka.

BUS tOpoLOgY???????

A bus network topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus. There are several common instances of the bus architecture, including one in the motherboard of most computers, and those in some versions ofEthernet networks.

ring TOPoloGy??????????

A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node - a ring. Data travels from node to node, with each node along the way handling every packet.

Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link^[1]. A node failure or cable break might isolate every node attached to the ring. FDDI networks overcome this vulnerability by sending data on a clockwise and a counterclockwise ring: in the event of a break data is wrapped back onto the complementary ring before it reaches the end of the cable, maintaining a path to every node along the resulting "C-Ring". 802.5 networks -- also known as IBM Token Ring networks -- avoid the weakness of a ring topology altogether: they actually use a star topology at the physical layer and a Multistation Access Unit (MAU) to imitate a ring at the datalink layer.

STar TopOLOgy????

Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer, which acts as a conduit to transmit messages.^[1] Thus, the hub and leaf nodes, and the transmission lines between them, form a graph with the topology of a star. If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.
The star topology reduces the chance of network failure by connecting all of the systems to a central node. When applied to a bus-based network, this central hub rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected. ^[2]
It is also designed with each node (file servers, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator.

Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It is also acts as a repeater for the data flow. This configuration is common with twisted pair cable. However, it can also be used with coaxial cable or optical fibre cable.

how to install OFFICE2007

Step 1: Insert the Microsoft Office 2007 Enterprise CD. If the Setup Wizard does not automatically begin, then click Start > Run > D:\setup.exe

Step 2: Enter the Product Key from the back of the CD jacket. Note: This is a unique code. Please keep in a safe place!

Click Continue.

Step 3: Check the box "I accept the terms of this agreement" and click the Continue button.

Step 4: Choose an installation option, Upgrade (removes Office 2003) or Customize (keeps Office 2003 installed and adds Office 2007, allowing you to use them both).

Note: Outlook 2003 will be uninstalled in either option. Outlook will be updated and your user settings and mail will migrate to the new version.

If you click Upgrade, go on to Step 5.

If you click Customize, go on to Step 4a.

Step 4a: Click the radio button for "Keep all previous versions."

Click the Installation Options tab, left-click the first drop down box and click Run all from My Computer

Click Install Now.

nish.

Step 5: Installation will begin. It may take 15-30 minu

tes to finish.

Step 6: Click Close to complete the installation.

Step 7: The first time you launch any Office program, you will be prompted to activate the software. As long as you have an active Internet connection, choose the default option and click Next.

Step 8: When the activation finishes, click Close.

Step 9: Click OK to finish.

AntivRUS INstall

If you don't know what your operating system is perform the following steps:

1. Click the Start button and select Run.

2. Type winver into the run box shown below then click the OKbutton.

3. If you get a window that looks like the one below then you haveWindows XP. Click on the link to go to the instruction page.

4. If you get a window that looks like the one below then you haveWindows 2000. Click on the link to go to the instruction page.

5. If you get a window that looks like the one below then you haveWindows Vista. Click on the link to go to the instruction page.

PRImARY storaGE

Primary storage (ormain memory orinternal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.

Historically, early computers used delay lines, Williams tubes, or rotatingmagnetic drums as primary storage. By 1954, those unreliable methods were mostly replaced by magnetic core memory, which was still rather cumbersome. Undoubtedly, a revolution was started with the invention of atransistor, that soon enabled then-unbelievable miniaturization of electronic memory via solid-state silicon chip technology.

This led to a modern random-access memory (RAM). It is small-sized, light, but quite expensive at the same time. (The particular types of RAM used for primary storage are also volatile, i.e. they lose the information when not powered).

As shown in the diagram, traditionally there are two more sub-layers of the primary storage, besides main large-capacity RAM:

• Processor registers are located inside the processor. Each register typically holds a word of data (often 32 or 64 bits). CPU instructions instruct the arithmetic and logic unit to perform various calculations or other operations on this data (or with the help of it). Registers are technically among the fastest of all forms of computer data storage.
• Processor cache is an intermediate stage between ultra-fast registers and much slower main memory. It's introduced solely to increase performance of the computer. Most actively used information in the main memory is just duplicated in the cache memory, which is faster, but of much lesser capacity. On the other hand it is much slower, but much larger than processor registers. Multi-level hierarchical cache setup is also commonly used—primary cache being smallest, fastest and located inside the processor; secondary cachebeing somewhat larger and slower.

Main memory is directly or indirectly connected to the central processing unit via a memory bus. It is actually two buses (not on the diagram): an address bus and a data bus. The CPU firstly sends a number through an address bus, a number called memory address, that indicates the desired location of data. Then it reads or writes the data itself using the data bus. Additionally, a memory management unit (MMU) is a small device between CPU and RAM recalculating the actual memory address, for example to provide an abstraction of virtual memory or other tasks.

As the RAM types used for primary storage are volatile (cleared at start up), a computer containing only such storage would not have a source to read instructions from, in order to start the computer. Hence, non-volatile primary storage containing a small startup program (BIOS) is used to bootstrap the computer, that is, to read a larger program from non-volatile secondary storage to RAM and start to execute it. A non-volatile technology used for this purpose is called ROM, for read-only memory (the terminology may be somewhat confusing as most ROM types are also capable of random access).

Many types of "ROM" are not literally read only, as updates are possible; however it is slow and memory must be erased in large portions before it can be re-written. Some embedded systems run programs directly from ROM (or similar), because such programs are rarely changed. Standard computers do not store non-rudimentary programs in ROM, rather use large capacities of secondary storage, which is non-volatile as well, and not as costly.

Recently, primary storage and secondary storage in some uses refer to what was historically called, respectively, secondary storage andtertiary storage

seCONDARY sTORAGE

Secondary storage (orexternal memory) differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/outputchannels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage does not lose the data when the device is powered down—it is non-volatile. Per unit, it is typically also two orders of magnitude less expensive than primary storage. Consequently, modern computer systems typically have two orders of magnitude more secondary storage than primary storage and data is kept for a longer time there.

In modern computers, hard disk drives are usually used as secondary storage. The time taken to access a given byte of information stored on a hard disk is typically a few thousandths of a second, or milliseconds. By contrast, the time taken to access a given byte of information stored in random access memory is measured in billionths of a second, or nanoseconds. This illustrates the very significant access-time difference which distinguishes solid-state memory from rotating magnetic storage devices: hard disks are typically about a million times slower than memory. Rotating optical storage devices, such as CD and DVDdrives, have even longer access times. With disk drives, once the disk read/write head reaches the proper placement and the data of interest rotates under it, subsequent data on the track are very fast to access. As a result, in order to hide the initial seek time and rotational latency, data are transferred to and from disks in large contiguous blocks.

When data reside on disk, block access to hide latency offers a ray of hope in designing efficient external memory algorithms. Sequential or block access on disks is orders of magnitude faster than random access, and many sophisticated paradigms have been developed to design efficient algorithms based upon sequential and block access . Another way to reduce the I/O bottleneck is to use multiple disks in parallel in order to increase the bandwidth between primary and secondary memory.^[2]

Some other examples of secondary storage technologies are: flash memory (e.g. USB flash drives or keys), floppy disks, magnetic tape, paper tape, punched cards, standalone RAM disks, andIomega Zip drives.

The secondary storage is often formatted according to a file system format, which provides the abstraction necessary to organize data into filesand directories, providing also additional information (called metadata) describing the owner of a certain file, the access time, the access permissions, and other information.

Most computer operating systems use the concept of virtual memory, allowing utilization of more primary storage capacity than is physically available in the system. As the primary memory fills up, the system moves the least-used chunks (pages) to secondary storage devices (to aswap file or page file), retrieving them later when they are needed. As more of these retrievals from slower secondary storage are necessary, the more the overall system performance is degraded.

opERATing SYSTem

operating system is the software on a computer that manages the way different programs use itshardware, and regulates the ways that a user controls the computer.^[1][2] Operating systems are found on almost any device that contains a computer with multiple programs—from cellular phones and video game consolesto supercomputers and web servers. Some popular modern operating systems for personal computers includeMicrosoft Windows, Mac OS X, and Linux^[3] (see also: list of operating systems,comparison of operating systems).

Because early computers were often built for only a single task, operating systems did not exist in their proper form until the 1960s.^[4] As computers evolved into being devices that could run different programs in succession, programmers began putting libraries of common programs (in the form of computer code) onto the computer in order to avoid duplication and speed up the process. Eventually, computers began being built to automatically switch from one task to the next. The creation of runtime libraries to manage processing and printing speed came next, which evolved into programs that could interpret different types of programming languages into machine code. When personal computers by companies such as Apple Inc., Atari, IBM andAmigabecame popular in the 1980s, vendors began adding features such as software scheduling and hardware maintenance.

An operating system can be divided into many different parts. One of the most important parts is the kernel, which controls low-level processes that the average user usually cannot see: it controls how memory is read and written, the order in which processes are executed, how information is received and sent by devices like the monitor, keyboard and mouse, and deciding how to interpret information received by networks. The user interface is the part of the operating system that interacts with the computer user directly, allowing them to control and use programs. The user interface may be graphical with icons and a desktop, or textual, with a command line. Another similar feature is an Application programming interface, which is a set of services and code libraries that let applications interact with one another, as well as the operating system itself. Depending on the operating system, many of these components may not be considered an actual part. For example, Windows considers its user interface to be part of the operating system, while many versions of Linux do not.