Computing Science Information Systems Design & Development (Part 2 Computer Systems) National 5
Hardware & software Learning Intentions After studying this topic you should be able to understand and describe: Hardware requirements of information systems: input and output devices processor type and speed (Hz) memory (RAM, ROM) device types including supercomputer, desktop, portable devices (including laptop, tablet, smartphone) Software requirements of information systems: operating systems web browsers specific applications and/or utilities Input Devices Keyboard A keyboard is used to type data into a computer. This is a slow method of entering data compared to automatic methods. Mouse A mouse is used to move a pointer (or curser) on the screen to select items. 2
Microphone A microphone is used with a sound card to enter sound data into a computer. Touchpad A touchpad is a small pad with sensors to detect the movement and taps of a finger to move a pointer (or curser) around the screen and select items. Touch-Sensitive Screen Touch- Sensitive screens accept input when it detects human touch. Modern touch screens accept multi-finger motions to perform actions like zooming in/out. Digital Camera A digital camera is used to input digital images into a computer. The quality of the camera resolution is measured in megapixels. A midrange digital camera can capture around 16 megapixels. Digital Video Camera A digital video camera is used to capture and input videos into a computer. Like a digital still camera, the resolution of a digital video camera is measured in megapixels. 3
Scanner A scanner is used to input images on paper into a computer. The resolution of a scanner is measured in dots per inch(dpi). The resolution of a scanner is typically 600 4800 dpi. Webcam A webcam can capture video or still photos. They can be used in videoconferencing. The resolution of a webcam is usually low. Joystick A joystick is used for game playing and it allows you to control characters in the game. Graphics Tablet This allows the user to input free hand drawings directly into a computer. A stylus is used to draw the graphics. 4
Output Devices Monitors Liquid Crystal Display (LCD) and Thin Film Transistor (TFT) This is a low-power flat screen display that is usually used on palmtop and laptop computers. More expensive TFT (Thin Film Transistor) flat screen displays are often used with desktop computers. Digital Projector This is a device that displays the output of the computer onto a projector screen for the audience to clearly view. Projectors are widely used in classrooms. Inkjet Printer An inkjet printer created a printout by firing tiny droplets of quick drying ink onto the paper. This type of printer can incur lots of cost in replacing the ink cartridges; however inkjet printers are cheap to buy. Laser Printer A laser printer creates a printout by using a laser to make an electric charge of an image on a drum, which is then transferred onto paper using powder called a toner. A laser printer produces dry printouts at a faster speed than an inkjet. Flatbed Plotter A flatbed plotter creates very precise technical printouts. Architects often use these to print blueprints of building designs. Loudspeakers A loudspeaker is used with a sound card to output sound data from a computer. 5
Processors The processor type and speed is different depending on the type of computer system. Processor Type Processors were originally designed with one core, but modern computers often use dual core and quad core processors. Essentially this means that instead of a computer having one brain working, it has two or four (depending on the processor) working simultaneously. This is especially important for systems being uses for video editing; gaming or CAD drawing as lots of processing power is needed. Processor Speed One method of measuring a computer systems performance is to look at the clock speed of the processor. This is measured in Hertz (Hz) and it tells us how many instructions can be handled in any one second. For example; a computer with a clock speed of 3GHz can execute 3 billion instructions per second. 6
Computer Types There are many different types of computers that are used today and it is important that you can identify each of them along with its capabilities. Super Computer This is a very powerful computer system that has a very high processing speed and a massive amount of backing storage. They are used for tasks that require a large amount of data to be processed very quickly. Tasks include, weather forecasting, medical research and simulations of real life situations (e.g. detonation of nuclear weapons), to name a few. Super Computers are very expensive and are many times the size of a typical desktop computer. The backing storage capacities of these systems can be several petabytes! Desktop Computer This type of computer is small enough to fit on a desk, but is not portable. They require to be connected to an electrical socket, as they do not have their own source of power. Typically they consist of a mouse and QWERTY keyboard for input, and LCD, TFT or touchscreen monitor for output, and an internal hard drive for backing storage. Most also have various optical drives to make use of as well. Laptop Computer Laptops are becoming even more popular as their power increases and cost goes down. The specification of a typical laptop is slightly less than a typical desktop, with the main difference being that a laptop is portable. 7
Tablet Computer A tablet computer is a flat portable computer that uses a touchscreen rather than a physical keyboard for input. They are ideal for browsing the web, using social media and taking photographs. Tablets come with Wi-Fi and sometimes 3G/4G connectivity. Tablets do not use hard drives for backing storage; instead they use solid state or flash backing storage. Smartphone This is a mobile phone that (along with making calls and texting) can take photographs, play music and videos, access the Internet and run small applications (apps). Although these computer systems are not as powerful as the rest, their size and functionality make them very popular. 8
Operating Systems The operating system (OS) is the most important part of system software. Without the operating system software the computer would be useless. All computers need an operating system to tell them how to work. The operating system software is the very first program or set of programs loaded when the computer is switched on. The operating system controls and monitors the operation of the computer system and how the hardware connected to the CPU is used. Software written for one operating system will not run on another operating system without being modified. Also, sometimes older software will not run on newer versions of the same operating system it was written for. Functions of an Operating System Error Reporting this will inform the user if a problem has occurred when trying to carry out an instruction. File Management organises the loading and saving of files to and from backing storage media into main memory. It also maintains an up-to-date index of where files are stored. Memory Management controls where programs and data are stored in memory without interfering with each other. Input / Output Management controls reading the keyboard and other input devices and controls the sending of data to output devices such as the monitor and printer. Device Drivers A device driver is a program that controls a particular piece of hardware that is attached to your computer. The purchase of a new printer or scanner may require the installation of the correct driver software to allow the device to function. A driver converts the instructions of the operating system to messages that the device (e.g. printer or scanner) can understand. 9
Utilities The operating system is just one type of system software. Another type of system software is utility software. Utilities are add-on programs that work with the operating system and add extra commands, functions or options for the user. A utility is a program that performs a very specific task, usually related to managing the resources of the computer system. Virus Checker This software checks the system for viruses against a database of known viruses and prevents the spread of them. Disk Fragmentation Most modern filing systems save files wherever they can on a disc. They will attempt to save a file in consecutive sectors but, as time goes on and files are saved and/or deleted, this isn't always possible. So the file will be saved with part of it in one sector, another part in a sector in a different part of the disc etc. This will obviously slow down the loading of the file as the drive head will keep having to move to different parts of the disc to load the file. A 'defragger' is a utility program, which moves files (and parts of files) around the disc until each file is stored in consecutive sectors with no fragmentation. 10
STORAGE Learning Intentions After studying this topic you should be able to understand and describe the benefits and applications of the following: Storage: Local, portable and cloud-based storage Storage capacity (in appropriate units) Magnetic and solid state storage devices Optical storage media - rewritable, read-only Interfaces: Interface type including USB Data transfer speed Backing Storage Devices Magnetic Storage Devices Hard Disk Data is stored by magnetising the surface of flat, circular plates that constantly rotate at high speed (typically 60 to 120 revolutions per second). A read/write head floats on a cushion of air a fraction of a millimeter above the surface of the disk. The drive is inside a sealed unit because even a speck of dust could cause the heads to crash. This is a high-capacity (500Gb 3Tb) magnetic storage device. A hard drive has a fast data transfer rate. Magnetic Tape Drive Magnetic tape is another magnetic storage device. This has a slow data transfer rate, fairly high-capacity magnetic backing storage device and is often used for backing up systems. 11
Optical Storage Devices Data is written into the disk by burning a permanent pattern on the surface using a laser beam. Data is read using a laser of low intensity. CD-ROM (Read Only) The data is put on the disc at manufacture, after which it can be read but not written to. The capacity of a CD-ROM is 750 MB. CD-R (Recordable) This optical disc allows data to be written to it but only once. Again the capacity is 750MB. CD-RW (Rewritable) This optical disc can be read and written to over and over again. DVD-ROM This is a high capacity optical disc (4.7GB) with a faster data transfer rate than a CD-ROM. Recordable and Rewritable discs are also available (DVD-R and DVD-RW). Blu-Ray Blu-Ray is used to store high quality feature length films as they have a very high capacity of approximately 25GB. 12
Solid State Devices Solid-state memory devices have no moving parts and are made up entirely of electronic components hence they provide extremely fast access to data. Memory Cards These are often used in digital cameras, digital video cameras and mobile phones to store and transfer data. The typical capacity of memory cards range from 2GB 32GB: depending on the capabilities of the device. USB Flash Drive USB Flash Drives are high-capacity storage devices that can be used to backup data and transfer data easily between computers. The typical capacity is 4GB 32GB although higher capacity drive can be purchased for a substantial amount of money. Cloud Storage Cloud Storage uses online services to store large amounts of data on the Internet or a remote computer network. This storage can be used to store personal emails, photo files or to back up data. This centrally stored data can also be used to synchronise data between personal devices such photos and address books. 13
Access Methods Just like input and output devices, backing storage can be compared in terms of capacity and the speed of data transfer. As well as these forms of comparison, they can also be compared by their types of access: Sequential or Direct/Random. Sequential Access Sequential Access is where other data has to be gone through to get to the required data. Magnetic Tape uses sequential access since you have to wind through other parts of the tape to get to the required data. For this reason sequential access is very slow. Direct / Random Access Direct / Random Access is where the read / write head can go straight to the required data. The hard disc has direct / random access since the read / write head can go straight to any part of the surface of the disc to read and write data. In fact, all forms of backing storage except magnetic tape are considered direct / random access. Direct / Random access is very fast. 14
Interface Types In order for peripheral devices to communicate with the CPU they need to be interfaced. An interface is a unit that sits between the CPU and a peripheral device and compensates for differences in speed, codes and other characteristics, to ensure compatibility. In terms of backing storage, different interface types have different rates at which they can transfer data from the device to the CPU. Interface Data Transfer Rate Time to transfer 1 GB of data USB 2.0 480 Mbps 15 seconds USB 3.0 5 Gbps 1.4 seconds Bluetooth 24 Mbps 5 minutes Firewire 800 Mbps 9.5 seconds Thunderbolt 10 Gbps 0.7 seconds 15
NETWORKS & CONNECTIVITY Learning Intentions After studying this topic you should be able to understand and describe the features and differences between: Stand-alone and networked computers Local Area Networks, Wide Area Networks and The Internet Peer-to-peer and client/server networks Wired, optical and wireless methods of transmitting data Network Types Stand Alone Computer This is a computer system that is completely independent and not connected to a network, Client / Server Networks Lots of networks are set up as client/server networks. A client is a workstation on the network. A server is central to this set up. It is a computer that has a fast processor and lots of memory and is used to control the resources that the client workstations can use. A server can be used for a while range of tasks. Tasks include: Managing the printing on a network Storing all the data files and application software Managing the clients access to the internet 16
Peer-to-Peer Networks In Peer-to-Peer networks there is no central server, each PC is equal on the network, each machine runs its own software and saves its own data. However, PCs are connected and can share data and peripherals to a small number of other users on the network. Each user decided which files on their machine can be shares and whether they are read only or read/write. Each user also decides which peripherals can be shared with other network users. If a computer is switched off then their shared resources are no longer available to others on the network. There is no central manager and each user is responsible for his or her own backups. Security is very low level. Summary Peer-to-Peer Every node equal Share peripherals / send messages Users choose which resources/files will be shared to others on network Each user responsible for backups Low security Client / Server Central server controlling access Share peripherals / send messages Files available on server Backup organised centrally High level of security User activities logged Requires a Network Manager 17
LANs, WANs and The Internet LAN (Local Area Network) Cover a small are such as one room or building Advantages: Share data Share peripherals Email Passwords keep data secure Different levels of access Flexible access Many users can use the same document at the same time Transmission Media: LAN stations can be connected by cables or by wireless technology. Cables Unsheilded Twisted Pair (UTP) Optical Fibre Wireless Infrared Communication Bluetooth WIFI WAN (Wide Area Network) Connect computers across large distances This is spread across countries and cities worldwide using telecommunication links. They are similar to LANs but on a bigger scale. Transmission Media: Telecommunication links communicate information over distance using: Microwave Transmission Satellite Links Telephone network - Optical Fibre / Copper Wires a Network Security: Usernames and passwords Encryption Firewalls Physical Methods 18
Internet This is a Wide Area Network across the world, a worldwide networks or networks. It is the actual hardware, the servers, the cabling, the modems, the routers and so on. There are 5 main applications that run on the Internet: The Web (http) what most people call the Internet File downloading Chat Email Newsgroups An ISP (Internet Service Provider) is required to access the Internet. Hardware In order for a computer to connect to a network a Network Interface Card is needed. A NIC carries out tasks that are vital to connect your computer to a network. For example, it takes data coming in from the network to your computer and passes it on to the processor Every device that is connected to the network will need a NIC, from computer to printer and scanner. 19
Transmission Media This is the type of connection used to link computers together in a network. Bandwidth Bandwidth is used to describe the speed of data transfer over the connection. Wired A wired network uses cables to transmit data across the network. Unshielded Twisted Pair (UTP) is typically used on LANS. Optical Fibre Fibre Optic cables send data in the form of light waves. They have a much higher bandwidth and are used on networks that carry a high volume of data. They are less prone to interference than electrical cables, but more expensive. Fibre-optic cables are often used over larger distances. Wireless This uses radio and microwaves to transfer data between computers. It is the common method used in the home and in small businesses. It allows the freedom of movement and there is less cable clutter. This type of connection is slower than wired and is considered less secure. Media Bandwidth Media UTP (Unshielded Twisted Pair) Optical Fibre Wireless Bandwidth 100Mbps 1Gbps 50Mbps 20