hi class welcome to st 2413 fundamentals of computing topic 1 a basic structure of computers objectives the overall objectives of this modules allow student to understand describe and explain the fundamentals of network communications client and server application and describe basic cloud computing services we also provide hands-on practice on linux operating system the link on the top right corner is a youtube video link on the introduction of google data center this is a sample of the how web application works they are some of the principal components of a web application linux operating system the linux operating system provides the platform for secure and reliable operation of the web server access to the file system is governed by file permissions and enforced by the operating system the operating system also provides interfaces to the networks and enforces process and user security apache web hosting service when a user requests a page or content from the web server apache receives the http request and interprets the contents for example apache will determine whether a file extension has been supplies as part of the request if so it will determine whether the requested resource is a static item's eg a simple web page stored as an html file or whether the requested item relates to an application eg a php file depending on the complexity of the requested item apache may be required to locate and respond with a number of resources eg the basic html file css files javascript images and other media like mp3 audio files of swf video files apache determines where to locate the content based on the path specified in the http request and the file pads identified in the html content php programming language one of the most popular scripting languages is php and there are wide range of applications available including content management systems cms like joomla forums bulletin boards shopping carts etc for a dynamic site the apache web server is configured to recognize when a script needs to be run this may be through a combination of file extensions and default settings for example if a website's home page is requested and the server has php installed apache will seek an index.php file in the root directory if there is no index.html file in the website root directory it is this mechanism which is used to initialize applications like joomla the php scripts will be used to store and retrieve information and to render the html page layouts for transmission back to the user's browser by the apache web server mysql database typically a php website will also use a mysql database to store content and configuration information it is possible to build sites where the contents are stored in flat text files but the use of relational data apps is like mysql gives greater flexibility the interaction between the apache web server and the mysql database is handled by php other components there may be a number of other components and applications hosted on the server these may include compiled applications for delivery of specialist media or graphic content or for rendering images and animations a common application on linux servers is email and this may be provided with a webmail interface via apache and or direct connections using pop ans smtp protocols overview of computer concepts most devices encountered when working with a network involve a computer the most obvious devices are workstations pcs and laptops and network servers running operating systems such as windows linux unix and mac os however devices also includes routers and switches these are specialized computers used to move data from computer to computer and network to network you will learn more about them in later chapters basic functions of a computer a computer's functions can be broken down into three basic tasks one input a user types the letter a on the keyboard which results in sending a code representing the letter a to the computer two processing the computer cpu determines what letter was typed by looking at the keyboard code in a table 3 output the cpu sends instructions to the graphics cards to display the letter a which is then sent to the computer monitor components of a computer these are the components of a computer from left to right we have one input devices an input device is any hardware device that sends data to a computer allowing you to interact with and control it example keyboard and mouse two processing devices are the components responsible for the processing of information within the computer system example the cpu ram and hard drive three output devices take data from the computer system and convert it to a form that can be read by humans example monitor and printer input components input components can be common user controlled devices such as keyboards microphones webcams and scanners external interfaces such as serial firewire and usb ports can also be used to get input from external devices storage devices such as hard disks and cd slash dvds can also be considered as input components the following illustration are the example of the external interfaces processing components cpu knows a central processing unit is the computer's main processing component the cpu is in charge of executing instructions from computer programs such as word processors and from the computer's operating system current cpus are composed of two or more processors called cores a multi-core cpu is like a person with two brains multi-core cpus enable computers to carry out multiple instructions simultaneously in which results in better overall performance output components the most obvious output components are monitors and printers output components also include storage devices network cards and speakers external interfaces can also be considered as output components for example a disk drive connected to a usb port allows reading files from the disk input and writing files to the disk output storage components the more storage a computer has the better the performance most storage components are both input and output devices most people think of storage as disk drives cd ddd drives and usb flash drives there are two main categories of storage one short-term storage two long-term storage memory is a temporary place to hold instructions and data while the cpu processes both the example can be seen in this illustration ram short term storage as known as random access memory ram ram's content will disappear when the power to the computer is turned off ram is commonly known as short-term storage and volatile memory the amount of ram in a computer is crucial to the computer's capability to operate efficiently ram is also referred to as working storage if there's not enough ram to run a program the computer will use the disk drive to supplement virtual memory virtual memory part of disk storage can be set as virtual memory a cpu can only access data slash code in ram let's use data slash code are placed in virtual memory if the data slash code is needed by cpu then it will be moved from virtual memory to ram long term storage long term storage can maintains its data even when there's no power long-term storage is also commonly referred to as non-volatile memory examples of long-term storages are hard disks cds slash dvds and usb flash drives long-term storage are used to store document and multimedia files as well as application and os files amount of storage a computer needs depends on the type and quantity of files to be stored for example large amount of long-term storage is required to storage image and video files personal computer hardware there are four major component in pc personal computer the four major components are motherboard hard drive ram and bios cmos the motherboard and its component the following is the illustration of a physical motherboard the key components of a motherboard cpu socket this is where the cpu is installed pci bus expansion slot pci bus expansion slot is used to add functionality to a pc by adding expansion cards that have a peripheral component interconnect pci connect pci express expansion slots supersedes pci and supports faster data transfer speeds the larger slots are suitable for high performance expansions card such as graphics cards and disk controllers smaller slots are best suited for sound cards and network interface cards ram slots slots for install ram on the motherboard chipset with heat sinks consist of two chips referred to as north and south bridge these chips control data transfers between memory expansion slots io devices and the cpu heatsink placed on top of the chips is used to prevent overheating sata connectors is used for connecting hard drives and cd dvd drives that uses serial at attachment sata specification ide connectors functions the same as sata but it outdated as most of the computer system nowadays is using sata main power connector this connector is where the motherboard receives power from the system power supply computer bus fundamentals bus consists of a collection of wires carrying signals such as data address or control signal from one place to another on the computer all data that goes into or comes out of a computer goes through the motherboard there are buses between cpu and ram cpu and disk drives cpu and expansion slots computer bus fundamentals data bus is used to carry data signals from main memory ram to cpu and vice versa or from main memory ram to input output io devices vice versa address bus is used to carry address signals example a memory location or port slash interface where an input or output device is attached control bus is used to carry control signals example read or write from cpu to memory or port slash interface this is the layout of the different bus and how they carry signals between cpu memory and io devices this is an illustration of how cpu get data from the ram one cpu will firstly request ram to provide data in a specified address to the address bus two ram will then send the data within the address that cpu is requesting though the data bus difference between address bus and data bus the data bus carries the data to be stored while address bus carries the location to where it should be stored address bus is a part of the computer system bus that is dedicated for specifying a physical address when the computer processor needs to read or write from or to the memory it uses the address bus to specify the physical address of the individual memory block it needs to access the actual data is sent along the data bus similarly when the processor wants to read some data residing in the memory it will assert the read signal and set the read address on the address bus after receiving this signal the memory controller will get the data from the specific memory block after checking the address bus to get the read address and then it will place the data of the memory block onto the data bus data bus a data bus simply carries data typically the same data bus is used for both read slash write operations when it is a write operation the processor will put the data to be written onto the data bus when it is the read operation the memory controller will get the data from the specific memory block and put it into the data bus what is the difference between address bus and data bus data bus is bidirectional while address bus is unidirectional that means data travels in both directions but the addresses will travel in only one direction the reason for this is that unlike the data the address is always specified by the processor i o polling and interrupt we have many external devices attached to the cpu like a mouse keyboard scanner printer etc these devices also need cpu attention suppose a cpu is busy in displaying a pdf and you click the window media player icon on the desktop though the cpu does not have any idea when an event like this would occur but it has to respond to such inputs from the i o devices interrupt and pulling are the two ways to handle the events generated by the devices that can happen at any moment while cpu is busy in executing another process pulling and interrupt let cpu stop what it is currently doing and respond to the more important task polling and interrupt are different from each other in many aspects but the basic point that distinguishes pulling and interrupt is that in polling cpu keeps on checking i o devices at regular interval whether it needs cpu service whereas in interrupt the i o device interrupts the cpu and tell cpu that it needs cpu service hard drive fundamentals hard drive is a primary long-term storage component on your computer hard drive consists of magnetic disks called platters that store data in the form of magnetic pulses hard drive also stores the documents you use the applications that open those documents as well as the os your computer loads when it boots the following is an illustration of what is inside a hard drive actuator arm is a device which moves head arm assembly its task is not only to start and secure continuous movement of hard drive head assembly but also to fully control it securing in control of this movement is of crucial importance for performing elementary function of hard drives magnetic platters are the circular disks inside the hard drive where the ones and zeros that make up your files are stored read write heads is a device that reads senses and writes records data on a magnetic disk or tape for writing the surface of the disk or tape is moved past the read slash right head by discharging electrical impulses at the appropriate times bits are recorded as tiny magnetized spots of positive or negative polarity for reading the surface is moved past the read slash right head and the bits that are present induce an electrical current across the gap solid state drives ssds nowadays replaces hard drives due to high performance in terms of speed and reliability ssds use flash memory which does not have any moving parts and has faster access times however ssd is more expensive than hard drives ssd is commonly found in mobile devices high performance desktops and servers ram fundamentals ram is the main short term storage component on a computer ram has no moving parts so accessing data in ram is much faster than accessing data on a hard drive in general the more ram your system has the faster it will run bios cmos fundamentals bios known as basic input output system is a set of instructions located in a chip on the motherboard bios tells the cpu to perform certain tasks when power is first applied to the computer one of those instructions is to perform a power and self-test post a power and self-test post is a process performed by firmware or software routines immediately after a computer or other digital electronic device is powered on when a computer boots the bios program offers a chance to run the setup utility in order to configure hardware components this configuration is stored in a type of memory called complementary metal oxide semiconductor cmos computer boot procedure the following below is the sequence of the computer boot procedure one power is applied to the motherboard two the cpu starts three the cpu carries out the bios startup routines including the post power and self-test for boot devices as specified in the bios configuration are searched for an os 5. the os is loaded into ram six os services are started the fundamentals of network communication a computer network consists of two or more computers connected by some kind of transmission medium such as a cable or airwaves in order to access the internet a computer has to be able to connect to a network the next few slides will cover what is required to turn a standalone computer into a networked computer nic basics attaching a computer to a network requires nic which is known as network interface card to create and mediate the connection between a computer and the networking medium it contains mac address media access control address which is a unique identifier assigned to nic examples of networking medium might be copper wire fiber optic cable or airwaves a media access control address mac address of a device is a unique identifier assigned to a network interface controller and i see mac addresses are most often assigned by the manufacturer of network interface cards each is stored in hardware such as the cards read-only memory or by a firmware mechanism wireless nic wireless nic must be chosen according to type of wireless ap being used typical are wireless n 802.11 ac or 802.11 a b g n where the letter a b g n and a c refer to the wireless networking standard the device supports wireless nacs connect to network using service set identifier ssid ssid is the name assigned to the wireless network you may also need to enter a security key or a username and password depending on the network's security configuration types of computers there are typically five types of computers these five types of computers are one embedded computers two personal computers three servers and enterprise systems for super computers and grid computers five cloud computing this is a diagram of different computer components processor known as cpu consists of arithmetic and logic and control unit these two component our key component with make up the processor in chapter one b we will explore more on the heart of the computer before i end this theory video please take some time to watch this youtube video on how to identify the components inside a computer this is the end of theory topic one a basic structure of computers thank you very much for watching this video i will see you all in the next theory video