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• C O M P U T E R S Y S T E M S (CS) - ВС

• Computer systems will include the computer along with any software and peripheral devices that are necessary to make the computerfunction

• Multicomputer CS - ММВС

• Multiprocessor CS - МПВС

• 1) MISD – MULTIPLE INSTRUCTION SINGLE

DATA - МАГИСТРАЛЬНЫЕ

• 2) SIMD – SINGLE INSTRUCTION MULTIPLE DATA

- векторные

• 3) MIMD - MULTIPLE INSTRUCTION MULTIPLE

DATA -матричные

• Hardware

• The three main hardware components of a typical personal computer or workstation are the processor, main memory, and a set of I/O devices. The processor is responsible for executing instructions—for example, adding two numbers. The memory stores programs that are executed by the processor and data on which the program operates. For example, a program could be a Web browser processing a Web page. I/O devices are used to move data in and out of the computer systems. Examples of I/O devices are the monitor, keyboard, mouse,

hard disk, and a network interface card. These components are connected through data buses that can move data between the components. For example, before the processor can add two numbers, it may have to read the numbers from the memory over the memory bus that connects the processor to the memory (see figure). I/O devices are typically connected to the computer using an I/O bus, which in turn is connected to the memory bus. This means that the processor can read and write data on the I/O devices. Data can often also be moved directly between the I/O devices and main memory using a technique called "direct memory access" (DMA). In practice, DMA tends to be a faster way of moving data between I/O

devices and main memory than using the processor, in part because the data has to cross the memory bus only once.

• Let us look at the example of a Web browser receiving an HTML file from a Web server and displaying it on a monitor. The browser uses socket calls to establish a TCP connection with the Web server. The operating system establishes the connection and transfers the incoming data from the network I/O device to OS buffers located in main memory. The browser can then use "read" calls to copy the HTML file in its own data buffers, which are also located in main memory. After it has received the file, the browser can start interpreting the data in the file. As it determines how to display part of the file (for example, what text to display and what font size to use) it writes the necessary information over the I/O bus to the graphics I/O card that control the monitor.

• I/O devices come in two flavors. First, some devices are an integral part of the computer system—that is, they are physically built into the computer. The devices that are built in depend on the system, but they are typically devices that are either very inexpensive or essential. For example, the devices needed to support a keyboard, mouse, and hard disk are often built in. Ethernet network interfaces have become relatively cheap and essential in the office environment. For this reason, computer systems that are intended for office use often include these interfaces. An

alternative to built-in devices is to add devices incrementally. To support this, I/O buses typically have a small number of open slots. Users can purchase devices separately, and connect them to the I/O bus by inserting them in one of the open slots. Low-end systems typically have one or two I/O slots, while high-end systems can have four or more. I/O buses are typically standardized so I/O devices built by one vendor can be used in PCs built by other vendors. The I/O bus standard covers the connector type, the electrical characteristics for the pins, the protocol that is used to transfer data over the bus, and the form of the I/O device card.

• The following are examples of commonly used I/O buses.

• The Industrial Standard Architecture (ISA) bus is an older, slower bus that

is still widely used for slower I/O devices.

• Many PCs have a Peripheral Component Interconnect (PCI) bus, which is a high-end I/O bus. It typically supports data rates up to one Gigabit per second. Higher speed versions are also available for use in servers. High-speed network interfaces for PCs and workstations are typically designed for use in the PCI bus.

• The Small Computer System Interface (SCSI) is also a widely used I/O interface. Many versions of SCSI exist, covering a wide range of data rates. SCSI is primarilyused for storage devices.

• The Personal Computer Memory Card International Association (PCMCIA) is an international standards body that was founded to define standards for integrated circuit cards in mobile environments—that is, environments where size, power, and ruggedness are critical. While the original focus was on memory cards, most people are probably more familiar with the PCMCIA I/O interface standards. Most PCMCIA devices are slow speed (for example, modems or 10 Mbps Ethernets), but more recent standards support higher data rates (for example, 100 Mbps Ethernet).

• CPI –cycles per instruction, cycles, bandwidth,

• Performance = Instructions/Program * Cycles/Instructions * Time/Cycle

• Hard Disk Design

• Hard disk drives are made of a magnetic material that is in the shape of a thin

circular disk known as a platter. Hard disks typically have more than one platter.

Each platter usually holds equal amounts of data. For example, a sixty-gigabyte

hard drive may be built using three twenty gigabyte platters. A platter is singlesidedif data can be stored on one side of the platter and double-sided if data can

be stored on both sides of the platter. Data is stored on each platter in narrow

concentric circles known as tracks. For hard disk drives that have more than one

platter, the tracks with the same diameter on each platter form a cylinder. Tracks

may store anywhere from tens to hundreds of kilobytes of data. Because it is

inefficient to use an entire track to store a data item, tracks are physically divided

into equal sized sectors. The operating system divides a track into equal sized disk

blocks (also known as pages), which may be stored on one or more sectors.

IP Address Overview

Introduction to IP Addresses

Every machine on a network has a unique identifier.The unique identifier for a computer is called its IP address. Unique addressing allows communication

between end stations Introduction to IP Addresses UNIX Host

UNIX Host Company A Company B

3 Networking and Telecommunications Training Center

1) There are two standards for IP addresses: IP Version 4 (IPv4) and IP Version 6 (IPv6)

2) IPv6 uses 128 binary bits to create a single unique address on the network.

3) IPv4 uses 32 binary bits to create a single unique address on the network.

4) An IPv4 address is expressed by four numbers separated by dots.

1) 10101100 =2^7+2^5+2^3+2^2 =128+32+8+4= 172

2) 00010000= 2^4=16

3) 00000001= 2^0=1

4) 00000001= 2^0=1

AS result IP= 172.16.1.1

IP Address Classes

Class A:

Class B:

Class C:

Class D: for multicast

LECTURES

LECTURE #1

Introducton to Internet – technologies

The place of http in ISO/OSI model.

The mechanism of http trafic transport.

•

• As Hethmon notes in "An Illustrated Guide to HTTP, "the web is the largest client/server system implemented to date." It is also the most complex and heterogeneous one that must deal with multitudes of operating systems, human languages, programming languages, software, hardware, and middleware.

• What is a client/server system?

• A client/server system is a very keen way of distributing information across information systems like a local area network (LAN), a wide area network (WAN), or the Internet.

• A client/server system works something like this: A big hunk of computer (called a server) sits in some office somewhere with a bunch of files that people might want access to. This computer runs a software package (uh...also called a server unfortunately) that listens all day long to requests over the wires.

The "wires" is possibly a twisted pair network hooked into a local telephone company POP or a cable or fiber optics network hooked up to a corporate WAN or LAN that is also linked up to the national telecommunications/information infrastructure through a local telephone company. Whatever the case, the specifics of the information infrastructure is beyond the scope of this tutorial, but should be mentioned.

The "wires" is possibly a twisted pair network hooked into a local telephone company POP or a cable or fiber optics network hooked up to a corporate WAN or LAN that is also linked up to the national telecommunications/information infrastructure through a local telephone company. Whatever the case, the specifics of the information infrastructure is beyond the scope of this tutorial, but should be mentioned.

• Typically, these requests will be in some language and some format tha the computer understands, but in English sound something like, "hello software package running on a big hunk of computer, please give me the file called "mydocument.txt" that is located in the directory "/usr/people/myname".

• The "server software" will then access the server hardware, find the requested file, send it back over the wires to the "client" who requested it, and then wait for another request from the same or another client.

• Usually, the "client" is actually a software program, like Netscape Navigator, that is being operated by a person who is the one who really wants to see the file. The client software however, deals with all the underlying client/server protocol stuff and then displays the document (that usually means interpreting HTML, but we'll get there in just a bit) to the human user.

• The whole process looks something like the figure below:

• So if the web is a huge client/server system, what is the underlying client/server protocol that is used by the client software and the server software for communication?

• Well the client/server protocol used by the web is HTTP (HyperText Transport Protocol).

• HTTP is a protocol that is defined in several RFC´s (Request for Comments) located at the Internic and has had several generations worth of revisions (HTTP/09, HTTP/1.0 and HTTP/1.1).

• HTTP is a "request-response" type protocol that specifies that a client will open a connection to a server then send a request using a very specific format. The server will then respond and close the connection.

• The details of HTTP are less important for an HTML designer as they are to a web programmer, so we will not go into the specifics here (although they are available from the Illustrated Guide to HTTP referenced in the Resources section below). The main thing you need to know is that HTTP is a language spoken between your web browser (client software) and a web server (server software) so that they can communicate with each other and exchange files.

• As a web designer, you will deal much more with the other web protocol, HTML that is discussed next.

What is HTML?

HTML is the "mother tongue" of your browser.

To make a long story short, HTML was invented in 1990 by a scientist called Tim Berners-Lee. The purpose was to make it easier for scientists at different universities to gain access to each other's research documents. The project became a bigger success than Tim Berners-Lee had ever imagined. By inventing HTML he laid the foundation for the web as we know it today.

HTML is a language, which makes it possible to present information (e.g. scientific research) on the Internet. What you see when you view a page on the Internet is your browser's interpretation of HTML. To see the HTML code of a page on the Internet, simply click "View" in the top menu of your browser and choose "Source".

What can I use HTML for?

If you want to make websites, there is no way around HTML. Even if you're using a program to create websites, such as Dreamweaver, a basic knowledge of HTML can make life a lot simpler and your website a lot better. The good news is that HTML is easy to learn and use. In just two lessons from now you will have learned how to make your first website.

HTML is used to make websites. It is as simple as that!

Okay, but what does H-T-M-L stand for?

HTML is an abbreviation of "HyperText Mark-up Language" - which is already more than you need to know at this stage. However, for the sake of good order, let us explain in greater detail.

• Hyper is the opposite of linear. In the good old days - when a mouse was something the cat chased - computer programs ran linearly: when the program had executed one action it went to the next line and after that, the next line and so on. But HTML is different - you can go wherever you want and whenever you want. For example, it is not necessary to visit MSN.com before you visit HTML.net.

• Text is self-explanatory.

• Mark-up is what you do with the text. You are marking up the text the same way you do in a text editing program with headings, bullets and bold text and so on.

• Language is what HTML is. It uses many English words.

In this tutorial you will learn so-called XHTML (Extensible HyperText Mark-up Language) which, in short, is a new and more well-structured way of writing HTML.

Now you know what HTML (and XHTML) stands for let's get started with what it is all about: making websites.

Elements and tags

You are now ready to learn the essence of HTML: elements.

Elements give structure to a HTML document and tells the browser how you want your website to be presented. Generally elements consists of a start tag, some content, and an end tag.

"Tags"?

Tags are labels you use to mark up the begining and end of an element.

All tags have the same format: they begin with a less-than sign "<" and end with a greater-than sign ">".

Generally speaking, there are two kinds of tags - opening tags: <html> and closing tags: </html>. The only difference between an opening tag and a closing tag is the forward slash "/". You label content by putting it between an opening tag and a closing tag.

HTML is all about elements. To learn HTML is to learn and use different tags.

Can you show me some examples?

Okay, the element em emphasis text. All text between the opening tag <em> and the closing tag </em> is emphasised in the browser. ("em" is short for "emphasis".)

Example 1:

<em>Emphasised text.</em>

Will look like this in the browser:

Emphasised text.

The elements h1, h2, h3, h4, h5 and h6 is used to make headings (h stands for "heading"), where h1 is the first level and normally the largest text, h2 is the second level and normally slightly smaller text, and h6 is the sixth and last in the hierarchy of headings and normally the smallest text.

Example 2:

<h1>This is a heading</h1>

<h2>This is a subheading</h2>

Will look like this in the browser:

This is a heading

This is a subheading

So, I always need an opening tag and a closing tag?

As they say, there's an exception to every rule and in HTML the exception is that there are a few elements which both open and close in the same tag. These so-called empty elements are not connected to a specific passage in the text but rather are isolated labels, for example, a line break which looks like this: <br />.

Should tags be typed in uppercase or lowercase?

Most browsers might not care if you type your tags in upper, lower or mixed cases. <HTML>, <html> or <HtMl> will normally give the same result. However, the correct way is to type tags in lowercase. So get into the habit of writing your tags in lowercase.

Where do I put all these tags?

You type your tags in an HTML document. A website contains one or more HTML documents. When you surf the Web, you merely open different HTML documents.

If you continue to the next lesson in 10 minutes you will have made your first website.

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