Information and Computer Technology Instructor: Sanchita Mal-Sarkar Course: IST 203

Computer An electronic machine that accepts input, processes data, stores data, and produces output. Data can be numbers, text, images, graphics, and sound, etc. Computer program is a set of instructions. Without it computer is useless. Programming languages allow us to write these instructions (e.g. C, C++, Java, etc).

Types of Computers: Microcomputers Computers are classified by their size, speed, and cost. Microcomputers - desktop or tower. - A notebook computer - Personal digital assistant (PDA) Minicomputers Mainframes supercomputers

Microcomputers Microcomputers => Also called personal computers. These computers are typically used by a single user, usually at home or at office. They can be of different shapes and sizes. A desktop or tower microcomputer costs about $2000. It can run on power from an electrical outlet. A notebook computer => small and light. Portable (standard desktop does not have). It can run on power from an electrical outlet or batteries. Expensive. Personal digital assistant (PDA) =>more portable than notebook computer. It has limited capability and not always a lower price.

Minicomputers Minicomputers => Somewhat larger than microcomputers. The computing capability of a microcomputer may be more than a minicomputer. Its cost can be between $20, 000 and $250, 000. Usually a company purchases a minicomputer when it needs to share large amount of data among many users. Each user inputs processing request s and views output through a terminal. The terminal has a keyboard for input and a display screen for output, but it does not process the user’s data. The processing requests will be transmitted from the terminal to the minicomputer.

Mainframes Larger and powerful than minicomputers. The mainframe computers can handle many more users than a minicomputer. These are used to provide centralized storage, processing, and management for large amounts of data. Its cost can be several hundred thousand dollars.

Supercomputers The largest and fastest computers. First developed for high volume computing tasks, such as weather prediction. These are also used in a large corporation because they can process tremendous volume of data in a relatively shorter time compared to other computers (microcomputers, minicomputers, and mainframes). However, its cost can be several million dollars.

Computer system A computer system consists of a computer, peripheral devices, and software. The computer itself can take care of the processing function, but it needs additional components, called peripherals, to accomplish its input, output and storage functions. Example of an internal peripheral device is hard disk drive.

Computer Hardware Hardware is the physical component of a computer. Hardware is the equipment used to perform the necessary computations. Examples: Main memory (RAM, ROM), secondary memory (hard disk drive, floppy disk drive), CPU, input devices (keyboard and mouse), and output devices (monitor and printer).

Hardware Components of a Computer System Central Processing Unit (CPU) Arithmetic-Logic Unit Control Unit Input Devices Secondary Storage Magnetic disk Optical disk Magnetic tape Keyboard Computer mouse Touch screen Source data automation Buses Output Devices Printers Video display terminals Plotters Audio output Communications Devices Primary Storage

Central Processing Unit (CPU) Coordinating all computer operations. Performs arithmetic and logical operations on data. To process a program stored in main memory, - CPU retrieves each instruction in sequence. - Interprets the instruction to determine what should be done. - Retrieves any data needed to carry out that instruction - Then CPU performs the actual manipulation. CPU’s current instruction and data values are stored temporarily inside the CPU in special high-speed memory locations called registers.

Central Processing Unit (CPU) The CPU consists of a control unit and an arithmetic-logic unit. Three kind of buses link the CPU, primary storage, and other devices in the computer systems. The data bus moves data to and from primary storage. The address bus transmits signals for locating a given address in primary storage. The control bus transmits signals specifying whether to read or write data to or from a given primary storage address, input device, or output device.

Data Bus, Address Bus, and Control Bus Central Processing Unit (CPU) Primary Storage 1 T U # 8 Arithmetic-Logic Unit 24 + 12 = 36 12 < 24 Control Unit Data Bus Address Bus Control Bus Output Devices Secondary Storage Input Devices

Computer Software Software consists of the computer programs that allow us to solve problems by providing sets of instructions. Examples: DOS, Windows, Mac. Office family, Lotus, Netscape, Internet Explorer, Virus scans, tax programs, computer games, GUI - Graphical User Interface.

Main Memory Computer memory is a set of storage locations on the main circuit board (motherboard). Four types of memory: RAM, Virtual memory, ROM, and CMOS (complementary metal oxide semiconductor memory)

Random access memory Consists of electronic circuits on the motherboard (main circuit board). Temporarily hold programs and data while the computer is on. Each circuit has address that is used by the microprocessor to transmit and store data. RAM is constantly changing (volatile). E.g. When we write a paper, the word processing program will be temporarily copied into RAM so that microprocessor can quickly access the required instructions.

Virtual Memory Today’s microcomputer software uses space on computer’s storage devices to simulate RAM if more needed. This extra memory is called virtual memory. How it works? Suppose my computer is running a word processing program that takes up most of the memory in RAM, but I want to run a spreadsheet program at the same time.

Virtual Memory (Cont.) The OS moves the infrequently used segment of the word processing program into virtual memory on disk. The spreadsheet program now can be loaded into RAM. If that segment is later needed, it is copied from virtual memory back to RAM. Disadvantage:It is much slower than RAM.

Read-only memory(ROM) Another set of electronic circuits on the motherboard inside the computer. We cannot increase ROM capacity. Manufacturer permanently installs ROM. When computer is on, the sets of instructions in ROM checks all the computer system’s components to make sure they are working and activates the essential software that controls the processing function.

Complementary metal oxide semiconductor(CMOS) A chip installed on the motherboard. Activated during the boot process. Contains information about where the essential software is stored. A small rechargeable battery powers CMOS. It changes every time we add or remove hardware to the computer system. CMOS is referred as semipermanent memory.

Secondary Storage Devices RAM retains data only when the power is on, so computer must have a more permanent storage option. The most common magnetic storage devices are hard disk drive, floppy disk drives, and tape drives.

Hard disk drive most computers contains one hard disk that cannot be removed from drive. Provides a storage area to be shared by all users of the computer. Generally, the programs that are needed to operate the computer system are stored here. Advantages over floppy disk: speed and capacity.

Hard Disk Drive Internal Components

Floppy disk drive Most common magnetic storage device. Users can have any number of floppy disks that can be inserted into computer’s floppy disk drive. High density disk- capacity to store 1.44 MB. Low-density disk - capacity to store 720 KB.

Tape drive Another magnetic storage device. Provides inexpensive archival storage for large quantities of data. Too slow to be used for day-to-day tasks. Used to make backup copies of data stored on hard disks. If a hard disk fails, data from the backup tape can be reloaded on a new hard disk.

Compact Disk Read Only Memory (CD-ROM) Optical storage device. Uses laser technology to read and write data on compact discs (CDs). High capacity and portability. Can store up to 680 MB, equivalent to more than 450 floppy disks. Disadvantage: The surface of the CD is not rewriteable like magnetic media. Once the laser cuts a pit in its surface, the pit cannot be recut, so the data stored there cannot be changed. Relatively slow access. Mainly used for software distribution and storing large data files such as graphics, animation, and video.

Input Devices Input device - keyboard, mouse. When we press a letter or digit key on a key board, that character is sent to main memory and displayed on the monitor. Keyboard consists of three major parts: main keyboard, keypads, and function keys. A mouse is a hand-held device used to select an operation.

Output Devices Shows the result of processing data. Output devices - monitor and printer. Monitor is the TV-like device that displays the output from a computer. Printer produces a hard copy of the text or graphics processed by the computer.

Processing Hardware The most important computer function is processing data. To understand this you need to learn how the computer represents and stores data. Computer does not understand human language because it is an electronic device that interpret every signal as either “on” or “off” like a light bulb.

Data representation Computer represents “on” with a 1 and “off” with a 0. These numbers are called binary digits or bits. Binary number system: most widely used method for interpreting bit settings as nonnegative integers. 38 (decimal) = 21 +22+25 = 00100110

Ones complement notation One of the widely used methods for representing negative binary numbers. A negative number is represented by changing each bit to the opposite bit setting. Example: 38 (decimal) = 00100110 (binary) -38 (decimal) = 11011001 (binary)

Twos complement notation Another popular method of representing negative binary number In this method, 1 is added to the ones complement representation of a negative number. Example: -38 (decimal) = 11011001 (ones complement) -38 (decimal) = 11011010 (twos complement)

Floating-point notation Usual method to represent real numbers Real number is represented by a number, called a mantissa, times a base raised to an integer power, called an exponent. Example: 387.53 = 38753 x 10 -2 Other possibilities .38753 x 10 3, 387.53 x100 (we choose mantissa is an integer with no tailing 0s)

Floating-point notation(cont.) A real number is represented by a 32-bit string. 24-bit for mantissa and 8-bit for exponent. Base is fixed to 10. Example 100 = 0000000000000000000000100000010 -387.53 = 11111111011010001001111111111110 387.53 = 00000000100101110110000111111110 ( 24-bit binary representation of 38753 is 000000001001011101100001 8-bit twos complement binary representation of -2 is 11111110)

Computer Software Computer hardware is useless without software. Software is the set of instructions and associated data that direct the computer to do a task. Software can be divided into two categories: system software and application software. System software helps the computer to carry out its basic operating tasks. Application software helps the user carry out a variety of tasks.

System Software Manages the fundamental operations of the computer, such as loading programs and data into memory, executing programs, saving data to disks, displaying information on the monitor, and transmitting data through a port to a peripheral device. Four types of system software: operating systems, utilities, device drivers, and programming languages.

Operating System Collection of computer programs that control the interaction of the user and the computer hardware. Responsible for directing all computer operations and managing all computer resources. Controls basic input and output, allocates system resources, manages storage space, maintains security, and detects equipment failure. A part of the operating system code is stored in a ROM and the rest of it resides on a disk. Loading the operating system into memory is called booting the computer.

Responsibilities of an Operating System Communicate with user, receive and execute commands, show error messages. Manage allocation of memory, processor time and other resources. Collect input from keyboard, mouse, and provide data to running programs. Convey program output to screen, printer, or other output device. Access data from secondary storage. Write data to secondary storage. Maintains security (checks user-name , password, virus infection)

Virus Virus => unscrupulous programmers deliberately construct harmful programs (called viruses) that instruct your program to perform destructive activities, such as erasing a disk drive. Virus protection software => Computer users can protect their computers by using virus protection software. How it protects? Virus protection software searches executable files for the sequences of characters that may cause harm and disinfects the files by erasing or disabling those commands.

Utilities Another category of system software. Augments the OS by taking over some of its responsibility for allocating hardware resources. Many utilities come with OS. Some independent software developers offer utilities for sale separately. E.g. Norton Utilities by Symantec.

Device driver A computer program that can establish communication because it contains information about the characteristics of your computer and of the device. Each peripheral device requires a device driver. Helps the computer communicate with that particular device. When we add a device to an existing computer, part of its installation includes adding its device driver to the configuration.

Computer programming languages Another type of system software. Programmer uses to write computer instructions. The instructions are converted into electrical signals that computer can manipulate and process. E.g. Basic, Visual Basic, C, C++, Cobol, etc.

Computer Languages: Machine Language Machine language: directly understood by a computer since it is a collection of binary numbers (0 and 1). Disadvantages: It is not standardized, different CPU needs different machine languages.

Assembly language One step above of machine language. More readable. Computer operations are represented by mnemonic codes rather than binary numbers. Variables can be given names rather than binary memory addresses. Disadvantage: CPU- dependent.

High -level languages CPU-independent. Combines algebraic expressions and English symbols. Disadvantage: computers do not understand. It must be translated into the target computer’s machine language before execution- compiler does the job.

Different High Level Languages Some of the high-level languages available include: FORTRAN for scientific programming, COBOL for business data processing, LISP for list processing, C for systems programming, Prolog for artificial intelligence, ADA for real-time distributed systems, Smalltalk for graphical user interfaces and object-oriented programming, and C++ for object-oriented programming.

Compiler Software that translates a high-level language program into machine language. Input to the compiler is a source file (created by word processor or editor) containing the text of a high-level language program. If it is syntactically correct, compiler will save in an object file which is a machine language instructions for the same job.

Linker All machine instructions are not complete. High-level language programs use at least one of the function that reside in other object files available to the system. Linker combines several object files, resolving cross references between the files, into one executable file (machine language program).

Loader To run an executable file, the loader must copy all the instructions into memory and direct the CPU to begin execution with the first instruction. As the program executes, it takes input data from source(s) and sends results to output devices.

Integrated development environment (IDE) Most high-level languages now include an Integrated Development Environment (IDE) consisting of a simple word processor, compiler, linker and loader tools for finding errors. This software package provides menus from which user can select the next step. It leaves all versions of the program in memory. For safety, we need to explicitly save the source file to disk.

Program Execution Executing a program requires the CPU to examine each program instruction in memory and send out the command signals required to perform each instruction. Although instructions are normally performed consecutively (sequencing), they can be skipped (branching) or repeated (looping) under program control. During execution, data can be entered by the operator, or from a saved file. After processing, the program output can be displayed or printed as a result.

Application software Developed for a specific task , such as word processing( MS Word/ WordPerfect), accounting (Lotus 1-2-3/ Excel), or database management (Access/ dBASE). We also use graphics and presentation software. Most applications are purchased on diskette or CD-ROM. They are installed by copying the programs from the diskettes/CD-ROM to the hard disk.

Spreadsheet Software Spreadsheet software is a numerical analysis tool. You can use spreadsheet software to main your checkbook register. Spreadsheet software creates a worksheet, composed of a grid of columns and rows. You can write any character in each column. You can write any number in each row. The intersection of a column and row is called a cell. Each cell has a unique address (cell reference). Using spreadsheet you can create graph (summary of data) Spreadsheet software provides you with excellent printouts of the raw data or graphs created from the data.

Database Management Software Most popular types of application software. A database is a collection of information stored in one or more computers. A structured database is organized in a uniform format of records and fields. A structured database contains data that describes a collection of similar entities. For examples, - student academic records, medical records. Name: Student# # of courses taken Spring 1999 GPA Student

Graphics and Presentation Software Graphics and presentation software allow us to create illustrations, diagrams, graphs, and charts that you also can print and transmit to remote computers. Most application software allows you to include graphics created by graphics software (Microsoft Paint or Adobe PhotoShop). You can also use clip art (a collection of drawings) comes with software packages. MS PowerPoint is a popular presentation software. You can create colorful presentations and transparencies.

Command-line & Graphical User Interfaces Command-line interface systems display a command prompt, then expect the user to type the desired commands. These systems include UNIX, MS-DOS and VMS. Graphical user interfaces (GUI) display pictures (icons), menus, and text, which the user may point to with a mouse or other pointing device, then click to select the desired function. These systems (GUI) include Macintosh OS, Windows 95/98, Windows NT, OS/2 Warp, and Unix with X Windows interface.

Data Communications The transmission of text, numeric, voice, or video data from one machine to another is called data communications. For example, Send an electronic mail to your friends around the globe. The four essential components of data communications are a sender, a receiver, a channel, and a protocol. Sender => The computer that originates the message is called the sender. Receiver => The computer at the message’s destination is called the receiver.

Data Communications Channel => The message needs some kind of medium to be transmitted. This medium is called channel. For example, telephone or coaxial cable, microwave signal, or optical fibers Protocol => The rules that establish an orderly transfer of data between the sender and the receiver are called protocols. Computer software and hardware establish these protocols at the beginning of the transmission, and both computers have to follow the protocols to ensure accurate transfer of data.

Data Bus Data bus => The communication between the microprocessor, RAM, and the peripherals is called the data bus.

Networks One of the most important types of data communications in the business world is a network connection. A network connects one computer to another computers and peripheral devices to share data and resources. There is a number of network configurations. local area network (LAN) => computers and peripheral devices are located relatively close to each other, generally in the same building. Client/server networks =>Some networks have file servers (one or more computers) that act as the central storage location for programs and that provide mass storage for most of the data used on the network. A network with a file server is called a client/server networks.

Networks Peer-to-peer networks => When a network does not have a file server, all the computers essentially are equal, and programs and data are distributed among them. This is called a peer-to-peer network. Each computer that is part of the network must have a network interface card installed. This device creates a communication channel between the computer and the network. Network software is also essential to establish the communications protocols. Standalone computer => A microcomputer that is not connected to a network is called a standalone computer.

Telecommunications Allows us to send and receive data over telephone lines. A modem connects a computer to a telephone jack. At the sending site, modem converts the digital signal from a computer into analog (continuous wave) signals (sound waves) that can traverse ordinary phone lines (modulation). At the receiving site, a second modem converts the analog signals back into digital signals (demodulation).

Telecommunications

Internet The internet was originally developed for the government to connect the researchers around the world to share data. Today, the internet is the largest network in the world that connects millions of people in almost 200 countries. The use of internet: electronic mail => This is the capability to send a message from one user’s computer to another user’s computer where it is stored until the receiver opens it. Message passes through electronic links called gateways. World Wide Web (Web) => Web is a huge database of information that is stored on the network servers in places that allow public access. The information is stored as text files called web pages.

Internet Hyperlinks => a place on a computer screen that is programmed to connect to a particular file on the same network server, or on a network v=server on the other side of the globe. Web browsing => communication software that help us navigate the WWW is called web browsing software or web browser.