Chapter 2: software The instructions and associated data that direct the computer to perform a task. For example, a word processor and its associated dictionary or thesaurus are software. A report you create using a word processor is not software (it does not contain instructions for the computer.) A specific item of software is a software package. You purchase software and by the nature of the purchase become licensed to install and use it on a single computer. Most often, you are not supposed to install the same software package on more than one computer (single-user license). Some software comes with a multiple-user license for a specified number of users, priced per user. Other software comes with a site license which enables anyone at a particular location (university campus, hospital) to use it. Public domain software is owned by the public, not the author and can be duplicated and distributed freely. Shareware is owned by a software author, but the author distributes it for free. The author hopes that users will like it enough to purchase enhanced versions. The user may become a registered user for a small fee, or for a larger fee be entitled to upgrades and newer versions as they become available. 2 Major categories of software: System software helps the computer carry out its basic operating tasks (written for the computer to enable it to perform useful operations) - operating system, language compiler, software to control a CD ROM drive (or other peripheral unit). Applications software helps computer users perform specific tasks: word processing, payroll, inventory control, playing games, education. Most important piece of system software: operating system. It acts as a liason between the hardware and the application software, performing essential tasks for the application software such as retrieving data stored in files (accessing the hard disk, determining where file data is stored and transferring file data to main memory), printing reports (controlling the flow of information from memory to the printer). The operating system is also the interface between the user and the computer hardware and other software. Some operating system functions: Controls basic input and output - controls flow of data to and from computer and peripheral devices like keyboard, screen, printer, disk drives that may be used for program input or output. Allocate system resources - Allocates processor time so that more than one task can run at the same time and more than one person can use a multi-user computer at the same time. The goal is for each task or user to think he/she/it is using the computer by him/her/itself. Manages storage space - retrieves disk files for us when we request them, stores data in disk files, cleans up by deleting old files for us. Maintains security - May check our id and password before allowing us to log in to the computer. Allows us to specify access-rights for individual files and ensures that they are enforced. For each file, it is capable of denying access for reading to anyone who does not have read privileges and for denying the capability to update (rewrite) to anyone who does not have write privileges. Detects equipment failures - capable of monitoring the status of individual computer components and preventing operation if a component is not working properly. When you log on, checks status of main memory and all computer components. Displays a message if a comoponent does not appear to be working properly. Different operating systems: Microsoft windows: graphical user interface (GUI)- provides icons that you can directly manipulate on the screen using a pointing device and pull-down menus that you can use to easily issue a command. Uniform look to applicatons- scroll bars, buttons, dialog boxes. You can run more than one program at a time in separate windows and you can easily transfer data between them. Copy some data from one application to the clipboard and paste it to another. Windows 95 is current version. Apple computers pioneered the idea of an operating system based on a GUI. Apple Lisa computer in 1984 - bombed as a business computer. Basis for Macintosh which is especially popular in eductational environments. System 8 is current version. UNIX - developed by Bell laboratories in 1969. Popular in research environments and universities. Started on mainframes and minicomputers but also available for personal computers. Supports mutitasking and multiple users. Not inherently a GUI. Because the programming language C is part of UNIX, enables programmers to create programs that can easily be transported from one type of computer to the other (portable software). Also, you can use the same operating system on many different computers. Don't have to learn a different OS for each. Additional system software- utilities software designed to augment the operating system by providing a way for the user to control allocation of resources. Some are included with the operating system - software to format disks, copy disks, backup disks, detect viruses. Others you purchase separately - Norton utilities - used to repair injured disks, reshuffle storage space on a disk, making better utiliztion of storage, ram doubler, disk doubler. Device driver - software used to control a peripheral (outside the computer) device such as a CD-rom, mouse. Comes with the device, but you must install it on your disk so the computer can communicate with the device. Programming Language compilers - usually purchased separately. C comes with the UNIX operating system. APPLICATIONS SOFTWARE 4 categories productivity software - helps you to work more effectively includes word processing, scheduling, spreadsheets, data base software, electronic publishing and presentations (powerpoint). education and reference software encyclopedia on CD rom, Shakespeare's works, language learning program, SAT prep, web browsers entertainment software games business software Word processing software provides features like spell-checking (automatic or look under tools menu - pick spelling) and helps you pick the right word (look under tools menu - select thesaurus). Basically you type in text and it enters the letters you type in your document at the position of the cursor. When you get to the end of a line, it automatically wraps down to the next line. You don't need to press Enter or return - press Enter ONLY at the end of a paragraph. You can change type font (stype) and type size. You can highlight text by moving the mouse cursor over it. You can find words in your document by using the Find dialogue box (under Edit menu). Important word processing function: moving text from one place in the document to another - let's you rearrange paragraphs. Called cutting and pasting - you do this in the following way: 1. Use your mouse to highlight the text to be moved. 2. Select Cut option from the Edit menu. 3. Move the mouse cursor to the spot where you wish to place the cut text. 4. Select paste from the Edit menu. In step 2, if you select copy instead of cut, you can make a copy of the highlighted text elsewhere in your document by following steps 3 and 4. Word also helps you create tables. You can insert pictures from special files and equations as well. You can set Word up so your document is saved to disk periodically (a dialogue box opens every 10 or 15 minutes). If you don't have this feature turned on, remember to save the document you are working on; otherwise, you will lose it (its in memory) if the computer loses power. The dialogue box looks like: save now O yes Yes O postpone |______| minutes Cancel Spreadsheet software - you see a grid of rows and columns on the screen - the software helps you fill it in and specify computations across row and column boundaries (more on this later). database management software - helps you store information in an organized way. All the information about a person place or thing is called a record. Like an electronic rolodex or card catalogue. You can retrieve what you want by making a query. You can insert new items (new records). You can update or change records easily (change an employee's marital status from single to married or from married to divorced). You can selectively retrieve certain records - for example, all friends who have birthdays in June. You can create a report of selected items - all workers who worked more than 10 hours overtime during the past week. You can sort or arrange the items in order according to more than one field or information category. Business software - helps an organization perform its tasks like payroll, accounting, inventory control. Different from productivity software which is oriented to the individual rather than the organization. Multimedia - an integrated collection of computer-based media such as text, graphics, sound, pictures, animation, video. A multimedia presentation usually comes on a CD rom because you need huge quantities of storage. You use a menu to select what you want to see or hear usually by moving you mouse cursor. Hypertext and Hypermedia The idea of hypertext is an information resource which consists of a collection of frames of information. Each frame of information may be linked to other frames in the collection. There are certain hot spots designated on each frame which are links to other frames. If you click on one of the hot spots, you will advance to the frame connected by that link. This allows the user to determine his/her own path through the information resource. World wide web is like this. Each home page is a frame of information about a person, place, or thing. You can get more detailed information about a certain aspect of that object by clicking on one of several highlighted phrases in the text describing the object. This takes you to another, related frame of information.