Al Manar Language School American Section 1st Quarter IT Revision Notes PDF

Al manar Language School American Section Lesson 1: Hardware and Software What is Hardware? Hardware is the physical parts of the computer system – the parts that you can touch and see. A motherboard, a CPU, a keyboard and a monitor are all items of hardware. What is Software? So...

Al manar Language School American Section Lesson 1: Hardware and Software What is Hardware? Hardware is the physical parts of the computer system – the parts that you can touch and see. A motherboard, a CPU, a keyboard and a monitor are all items of hardware. What is Software? Software is a collection of instructions that can be ‘run’ on a computer. These instructions tell the computer what to do. Software is not a physical thing (but it can of course be stored on a physical medium such as a CD- ROM), it is just a bunch of codes. An operating system such as Windows XP or Mac OS X, applications such as Microsoft Word, and the instructions that control a robot are all examples of software. Mrs. Alia Esmat Grade 9 Information technology The Difference Between Hardware and Software Computer hardware is the physical components that make up the computer system. Hardware is useless without software to run on it. Software is instructions that tell computer hardware what to do. Software is useless unless there is hardware to run it on. For a computer system to be useful it has to consist of both hardware and software. Mrs. Alia Esmat Grade 9 Information technology Lesson 2: Main Computer Components Central Processing Unit (CPU) The CPU is the 'brain' of the computer. It is the device that carries out software instructions. The Pentium processor made by Intel is an example of a CPU. CPUs usually plug into a large socket on the main circuit board (the motherboard) of a computer. They get very hot when they are operating so usually have a large fan attached to their top to keep them cool. The speed of a CPU is measured in Hertz (Hz). The speed generally corresponds to the number of actions the CPU can perform every second. 1 Megahertz (MHz) is 1,000,000 (1 million) Hertz 1 Gigahertz (GHz) is 1,000,000,000 (1 billion) Hertz A typical, modern, fast CPU runs at around 2.8GHz. That means it can perform almost 3 billion actions every second! Main Memory Any data or instructions that are to be processed by the CPU must be placed into main memory (sometimes known as primary storage). Mrs. Alia Esmat Grade 9 Information technology Random Access Memory (RAM) Random Access Memory (RAM) is the part of the computer that temporarily stores the instructions that the computer is running, and the data it is processing. RAM is a volatile storage device. This means that if the computer’s power is turned off the contents of RAM disappear and are lost. RAM, like the CPU, also plugs in to sockets on the motherboard. When a computer is in use, its RAM will contain… 1. The operating system software 2. The application software currently being used 3. Any data that is being processed The storage capacity of memory is measured in Bytes. Usually RAM can hold millions of bytes of data, so you will see capacities measured in: Megabytes (MB) or 1,000,000 (1 million) Bytes Gigabytes (GB) or 1,000,000,000 (1 billion) Bytes So, if a computer has 2GB of RAM, it can hold 2 billion bytes of data and instructions at any time. Mrs. Alia Esmat Grade 9 Information technology Read-Only Memory (ROM) Read-Only Memory (ROM) is used in most computers to hold a small, special piece of software: the 'boot up' program. This software runs when the computer is switched on or 'boots up'. The software checks the computer’s hardware and then loads the operating system. ROM is non-volatile storage. This means that the data it contains is never lost, even if the power is switched off. This 'boot up' software is known as the BIOS (Basic Input Output System) Peripheral Devices Technically, a computer need only be made up of a CPU and some RAM. But a computer like this would not be much use to anybody – other devices need to be connected to allow data to be passed in and out of the computer. The general name for these extra devices is ‘peripheral devices’. They are usually categorised into input devices, output devices and storage devices. Mrs. Alia Esmat Grade 9 Information technology Lesson 3 : Input and output devices What Are Input Devices? Devices that pass data into the computer are known as input devices. A keyboard, a mouse and a webcam are all examples of input devices. They all take information from the outside world (key presses, hand movements, images), convert them into data and then send this data into the computer for processing. What Are Output Devices? Devices that take data from the computer are known as output devices. A monitor, a printer and a loudspeaker are all examples of output devices. Mrs. Alia Esmat Grade 9 Information technology They all take information from the computer and convert it into real world things (images, paper hardcopy, sound). What is Secondary / Backing Storage? Secondary storage (sometimes called backing storage) is the name for all of the devices (apart from ROM and RAM) that can store data in a computer system. A hard drive, a CD-ROM, a floppy disc and a USB memory stick are all examples of secondary storage devices. Secondary storage is non-volatile, so data that is stored on these devices remains there safely. Mrs. Alia Esmat Grade 9 Information technology Lesson 4: What is an Operating System? An operating system is a special piece of software that manages the general operation of a computer system: It provides a user interface so that we can interact with the computer It manages applications that are running on the computer, starting them when the user requests, and stopping them when they are no longer needed It manages files, helping us save our work, organise our files, find files that we have saved and load files It manages the computers memory, deciding what should be loaded into memory and what should be removed Without an operating system, a computer is of little use. But, just having an operating system running alone on a computer is also not very useful - we need to have application software (such as Word, Excel, etc.) so that we can actually do useful tasks with the computer. Useless! On its own, the hardware of a computer is a fairly useless lump of plastic and metal! It Works! Mrs. Alia Esmat Grade 9 Information technology (But it's not very useful) Add in an operating system and you have a computer that actually works. Useful! To do any useful work you will also have to add application software. Operating systems that you may have heard of: Windows XP Windows Vista Mac OS X Linux Mrs. Alia Esmat Grade 9 Information technology Lesson 5: User Interfaces The system that people use to interact with a computer (to give it commands, to see the results of those commands, etc.) is known as the user interface. There are two that you need to be aware of: Graphical User Interface (GUI) Command-Line Interface (CLI) Graphical User Interface (GUI) A GUI is an interface built around visual (graphical) things: Windows are regions of the screen used to display information Icons are small pictures that are used to represent folders, software, etc. Menus are lists of options the user can select from A pointer is an arrow that can be moved around the screen and is used to select things Windows XP is an example of an operating system with a GUI. GUIs are quite easy to use due to the visual nature of the interface – the user has lots of visual clues as to what things do. However, to display all of the nice graphics required by a GUI Mrs. Alia Esmat Grade 9 Information technology takes a lot of computing power so quite a powerful computer is needed. A GUI is sometimes called a WIMP interface: Windows, Icons, Menus, Pointer Command Line Interface (CLI) Many years ago when computers were not very powerful they could not display the colourful graphics required for a GUI. The only interface available to most computer uses was the ‘command line’. The user would see nothing but a black screen. They would have to type a command to make anything happen. ************************************************ Mrs. Alia Esmat Grade 9 Information technology Lesson 6: Input and Output Devices Scanner A device that ‘scans’ images, book pages, etc. Scanning is basically taking a close-up photograph (just very slowly and with great detail). The scanned image data is passed to the computer. Scanned images can be further processed once inside the computer, e.g. OCR of printed text. Digital Camera A device that captures digital photographs. Most digital cameras do not directly input data into a computer - they store photographs on memory cards. The photographs can later be transferred to a computer. A digital camera in fact contains a small computer that controls camera focus, stores images, etc. Video Camera A device that captures moving images, or video. Like a digital camera, most video cameras do not directly input data into a computer – the captured movies Mrs. Alia Esmat Grade 9 Information technology are stored on video-tape or memory cards and later transferred to a computer. Web Cam This is a very basic video camera used to feed live video into a computer. The video data from a web cam is low quality compared to a full video camera. However it is good enough for web chats (e.g. using a messenger application such as MSN Messenger or Skype)., Microphone An input device that converts sound into a signal that can be fed into a computer. The signal from a microphone is usually analogue so, before it can be processed by a computer, it must be converted into digital data. An Analogue-to-Digital Convertor (ADC) is used for this (usually built into the computer’s sound card) Many headphones now come with microphones to allow them to be used with chat and phone applications ******************************************* Mrs. Alia Esmat Grade 9 Information technology Lesson 7: Output devices CRT Monitor A monitor displays text and image data passed to it by the computer. A cathode-ray tube (CRT) monitor is the type that has been around for years and is large and boxy. CRT monitors are heavy and they take up a lot of desk space. They have largely been replaced by flat-screen monitors. However some are still used in the design industry since the colour accuracy and brightness of CRT monitors is excellent, and designers need to see true-to-life colours. Also, CRT monitors are generally cheaper than flat-screen monitors. Flat-Screen Monitor (TFT or LCD) Over the past few years, as they have come down in price, flat-screen displays have replaced CRT monitors. Flat-screen monitors are light in weight and they take up very little desk space. Modern flat-screen monitors have a picture quality that is as good as CRT monitors. Mrs. Alia Esmat Grade 9 Information technology Digital / Multimedia Projector Digital projectors are used in situations when a very large viewing area is required, for example during presentations, for advertising, or in your home for watching movies. A projector connects to a computer, a DVD player or a satellite receiver just like a ordinary monitor. The image is produced inside the device and then projected out through a large lens, using a powerful light source. Loudspeaker If you want to hear music or sounds from your computer, you will have to attach loudspeakers. They convert electrical signals into sound waves. Loudspeakers are essential for applications such as music editing, video conferencing, watching movies, etc. Mrs. Alia Esmat Grade 9 Information technology Lesson 8: What is Data Storage? Main Memory Main memory (sometimes known as internal memory or primary storage) is another name for RAM (and ROM). Main memory is usually used to store data temporarily. In the case of RAM, it is volatile (this means that when power is switched off all of the data in the memory disappears). Main memory is used to store data whilst it is being processed by the CPU. Data can be put into memory, and read back from it, very quickly. Memory is fast to access, but only holds data temporarily... Backing Storage Backing storage (sometimes known as secondary storage) is the name for all other data storage devices in a computer: hard-drive, etc. Mrs. Alia Esmat Grade 9 Information technology Backing storage is usually non-volatile, so it is generally used to store data for a long time. Backing storage devices are slower to access, but can hold data permanently... The device that actually holds the data is known as the storage medium (‘media’ is the plural). The device that saves data onto the storage medium, or reads data from it, is known as the storage device. Sometimes the storage medium is a fixed (permanent) part of the storage device, e.g. the magnetic coated discs built into a hard drive Sometimes the storage medium is removable from the device, e.g. a CD-ROM can be taken out of a CD drive. Mrs. Alia Esmat Grade 9 Information technology  What is a Backup? A backup simply means making one or more copies of your data. For example, if you have a folder of photos stored on the hard- drive of your laptop, you might back them up by copying them to a CD-R. Note: If you move the photos from the hard-drive to a CD- R, you do not have a back-up – you still only have one copy of the photos, but now they are on a CD instead of the hard-drive. You only have a backup if you have a second copy of your data. How Are Backups Created? Personal backups of the data on your hard-drive can be made by… Burning files to a CD-R Copying files to an external hard-drive Copying the files to another computer on a network Businesses backup essential data by… Mrs. Alia Esmat Grade 9 Information technology  Making copies of data very regularly Using large-capacity media such as magnetic tape Automating the system so that nobody forgets to do it! Keeping backup media off-site (in case of fire or theft) ************************************ Mrs. Alia Esmat Grade 9 Information technology