Mencegah Inputan Kosonsg

Banyak website yang menyediakan fasilitasn bukutamu, contact us, registrasi, dan yang lainnya. Tetapi ada suatu hal kecil yang menyebabkan website itu kacau. Banyak orang yang iseng mengisikan karakter kosong, ketika mengisikan bukutamu, contact us, dll. Kalau hal ini dibiarkan terus-menerus, bisa-bisa database penuh dengan karakter kosong, menyebalkan bukan ???

Bagi seorang webmaster, pasti sudah tahu mengenai hal ini, dan pasti tahu caranya mencegah inputan kosong pada form isian. Untuk mencegah inputan kosong bisa menggunakan javascript.
scriptnya :

Javascript

<script>

function cekinput(){

var doc = document.tracer;

if (doc.field.value==""){

alert ("Anda belum mengisi");

doc.field.focus();

return false;

}

return true;

}

HTML

<form action="" onSubmit="return cekinput();" method="post" name="tracer">

<input name="field" type="text" class="field" id="nis" size="30">

<input name="input" type="submit" id="input" value=" Input ">

</form>

NIC (Network Interface Card)

NICs are considered Layer 2 devices because each individual NIC throughout the world carries a unique code, called a Media Access Control (MAC) address. This address is used to control data communication for the host on the network. You will learn more about the MAC address later. As the name implies, the NIC controls the host's access to the medium.

In some cases the type of connector on the NIC does not match the type of media that you need to connect to. A good example is your Cisco 2500 router. On the router you will see AUI (Attachment Unit Interface) connectors and you need to connect the router to a UTP Cat5 Ethernet cable. To do this a transceiver (transmitter/receiver) is used. A transceiver converts one type of signal or connector to another (e.g. to connect a 15-pin AUI interface to an RJ-45 jack, or to convert electrical signals to optical signals). It is considered a Layer 1 device, because it only looks at bits, and not at any address information or higher level protocols.

NICs have no standardized symbol. It is implied that whenever you see networking devices attached to network media, there is some sort of NIC or NIC-like device present even though it is generally not shown. Wherever you see a dot on a topology, there is either a NIC or an interface (port), which acts like at least part of a NIC.

Pawon Coklat

Hi Guys .... Sorry kalau posting ini terlambat, seharusnya posting ini beredar tanggal 14 Februari. Tapi no problem, karena ini masih bulan Februari. kamu-kamu semua pasti tahu ada apa dengan tanggal 14 februari ( Hari Valentine gituuuu ). Valentine biasanya identik dengan cokelat. Pasti tahu kan yang namanya Cokelat.

Nah ... kebetulan nie ... aku punya teman yang ngejual berbagai macam cokelat. Jadi ga usah bingung deh ... kalau mo pesen coklat. Tinggal telp atau email aja bisa kok. Lokasinya tu ada di Batang ( tepatnya di Jl. Tentara Pelajar Kalisalak Batang Telp. 02854494312 ), tetapi kala temen-temen di Semarang juga masih bisa kok pesennya, telp aje ke 081514408881. Kalau mo lihat site nya, liat aja di sini "http://pawoncoklat.blogspot.com". Selamat menikmati.

Network ??? What this .... ?

A computer network is an interconnection of a group of computers. Networks may be classified by what is called the network layer at which they operate according to basic reference models considered as standards in the industry such as the four-layer Internet Protocol Suite model. While the seven-layer Open Systems Interconnection (OSI) reference model is better known in academia, the majority of networks use the Internet Protocol Suite (IP) as their network model.

Computer networks may be classified according to the scale: Personal area network (PAN), Local Area Network (LAN), Campus Area Network (CAN), Metropolitan area network (MAN), or Wide area network (WAN). As Ethernet increasingly is the standard interface to networks, these distinctions are more important to the network administrator than the end user. Network administrators may have to tune the network, based on delay that derives from distance, to achieve the desired Quality of Service (QoS). The primary difference in the networks is the size.

Personal Area Network (PAN)
A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that may be used in a PAN are printers, fax machines, telephones, PDAs or scanners. The reach of a PAN is typically within about 20-30 feet (approximately 6-9 Meters). PANs can be used for communication among the individual devices (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink).

Personal area networks may be wired with computer buses such as USB[3] and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth.

Local Area Network (LAN)
A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library will have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) connect to the internet. All of the PCs in the library are connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnection devices and eventually connect to the internet. The cables to the servers are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbps.

All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbps Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.

The defining characteristics of LANs, in contrast to WANs (wide area networks), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 100 Gbit/s, and possibly 40 Gbit/s. Inverse multiplexing is commonly used to build a faster aggregate from slower physical streams, such as bringing 4 Gbit/s aggregate stream into a computer or network element with four 1 Gbit/s interfaces.

Campus Area Network (CAN)
A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.

This term is most often used to discuss the implementation of networks for a contiguous area. For Ethernet based networks in the past, when layer 2 switching (i.e., bridging (networking) was cheaper than routing, campuses were good candidates for layer 2 networks, until they grew to very large size. Today, a campus may use a mixture of routing and bridging. The network elements used, called "campus switches", tend to be optimized to have many Ethernet-family (i.e., IEEE 802.3) interfaces rather than an arbitrary mixture of Ethernet and WAN interfaces.

Metropolitan Area Network (MAN)
A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN

Wide Area Network (WAN)
A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

Bitmap Graphics

Bitmap graphics are made up of colored pixels. Pixels are very small rectangles (usually square, although in some video applications they are wider than they are tall) of varying colors that once put together give you an image. You can see from the example below that zooming in on a bitmap image reveals the pixels that make up the image when viewed at 100%.

Bitmap graphics are usually (but not always) photographic in nature, capable of subtle graduated tones - often in the range of millions of colors per image. The problem with bitmap graphics is that they don't enlarge well as Photoshop needs to guess what color the extra pixels should be - this can result is loss of definition and a dramatic lowering in quality, depending on how much you enlarge the image. Common file formats for bitmap image data include GIF, JPEG and PNG for Internet usage and TIFF for print usage. As you can see from the example below, physically enlarging an image will degrade quality.

Pixels are also used to display the image on your computer screen. Common pixel dimensions of computer displays are 1024 wide by 768 high and 1600 wide by 1200 high. The size of a bitmap graphic when viewed on your computer screen is defined by the number of pixels that make up the image - so an image that is 50 pixels wide will look very small on your screen at 100% viewing percentage, whereas an image that is 4000 pixels wide will be larger than your screen at 100% viewing percentage.

The printable dimensions of an image are defined by the DPI (dots per inch) - this information is invisibly embedded in the image file. Digital cameras often embed information such as this, that may include the conditions the image was taken in, and even the camera model used. This information is not actually visible in the image, and requires software such as Photoshop to read it.

You should not confuse the output DPI of your printer with this figure, which may range from 600-2400DPI - this refers to the density of the dots of ink laid down on the page by the printer. You don't have to prepare your images to 2400 DPI to get the best results - in fact doing so will significantly slow down printing as your file could potentially be huge! Often an image DPI in the range of 175-250 will give very good results on home printers. Images prepared for high quality commercial print are usually prepared at 300 DPI for up to A3 in size; whereas very large images (for instance on billboards) can be as low as 50 DPI, as they are not made to be viewed as closely as a magazine or small poster. There is no need to go above 300 DPI when creating images as you will yield virtually no improvement in output quality, only increasing the size of your file when saved.

It is easy to understand the relationship between pixel dimensions and DPI - put simply, the DPI is how many pixels will be printed in an inch - so you could actually think of DPI as PPI (pixels per inch). Indeed, many experts believe this to be the true definition of DPI, and that Photoshop should refer to it as such. However, the term DPI is used throughout the professional print industry, so this is why it is referred to as DPI in Photoshop, not PPI.