CHAPTER 1 Overview COMPUTER Programmable devices that can store, retrieve, and process data. COMPUTER DEVELOPMENTS- Smaller size - processors (vacuum tubes -> transistors ->IC chip) Microprocessor - miniaturized circuitry that processes the data, etched onto a sliver (chip) of silicon (found in sand). More powerful - miniaturization allows computer to house more components, processing over shorter "distances". Less expensive - miniaturization allows computers to be used more places and for more purposes mass production decreases price / assembly line used for smaller components. TYPES OF COMPUTERS - Supercomputer - Cray Research: CRAY J916 ($1 million and up) - Requires special staff and environment - Fastest, largest, costliest - Multi-user : 10,000 - Used for research, weather forecasting, aircraft design, simulation, special effects Mainframe Computers - Digital Equip Corp: VAX ($100,000 - $20 million) - Requires special staff and environment - Fast, large capacity - Multi-user : thousands of users - Used by large organizations - banks, univ, insurance co. - Smaller scale : used smaller organizations for card catalogues, accounting. Workstation -Hewlett-Packard Apollo, Sun Workstation ($2,000 - $10,000) - Souped-up PC - Mainframe speed at fraction of cost - Single-user or Multi-user : 1-100 or more - Used by engineers and scientists for CAD, high vol. number crunching Microcomputers - Gateway: Pentium 133; Apple: PowerBook notebook PC ($100 - $10,000) - Small, portable, desktop machine - Single User - typically - Used by individuals 1
HARDWARE Physical components of a computer. Input Hardware - Devices that allow data to be put into the computer. Keyboard Mouse, trackball, joystick Scanning device (fax, scanner) Processing Hardware - The component that is the brains of the computer. CPU - Central Processing Unit - controls and manipulates the data. Memory Hardware - The components that store operational data & information Primary Storage (main memory, RAM - Random Access Memory) -Components that store the programs and data that are actively being used. Characteristics: Electricity represents data & info Volatile - Changes when status of electricity changes Random Access to data & info Memory size determines the size of programs & data ROM - Read Only Memory (not volatile, not erasable) - Component that stores hardwired instructions to control basic operations "Boots up the computer" Related Information: Data - Organized into the following units Bits - Binary digit (electrical states) Byte - Character - group of 8 bits that represents a letter, number, or special symbol. Nibble 4 bits Word group of bits processed simultaneously (16 to 64 bits) Units of measure for data - byte - 1 character kilo - thousand mega - million giga - billion tera - trillion kilobyte (K) - 1024 characters megabyte (MB) - over 1 million characters gigabyte (GB) - over 1 billion characters terabyte (TB) - 1 trillion characters 2
Output Hardware - Devices that translate processed data into a form that humans can understand. Screen (monitor, CRT, flat-panel display) - softcopy Printer, plotter (dot-matrix, laser, ink-jet) - hardcopy Sound (beeps, tones, music, speech) Secondary Storage Hardware - Devices that store data & programs permanently. Drive - Device that reads & write data on medium. Backup - Duplicate copy of data stored on secondary storage. Magnetic Floppy Disk - Removable, round, flexible Magnetic Hard Disk Non-removable, round, metal disk Laser Optical Disk - Removable, round, hard plastic disk Magnetic Tape - Removable, flexible magnetic ribbon Communication Hardware - Devices that allow a computer to communicate with geographically separate devices. Modem - Modulator/Demodulator - Electronic device that allows a computer to communicate over the telephone lines. Cable - Allows computer to communicate directly with another computer or device. Fax Modem - Modem that allows computer to communicate with fax machine. Dumb Terminal - input, output & communication hardware only - Usually keyboard, monitor, cables with no processor. 3
SOFTWARE - (Programs) The executable step by step instructions that tell the computer how to perform a process or task. Application Software - Software that can perform useful work on general-purpose tasks. Examples: word processing, spread sheets System Software - (operating system) Software that enables the user and application software to interact with the computer. Helps manage computer resources. Examples: DOS, Windows NT, Linux, and VMS. PROGRAMMING Creating the step by step instructions to complete a task on the computer. Development of a program: Problem solving phase 1. Analysis and specification understanding the problem. 2. Designing the logic general solution (algorithm). 3. Verify follow algorithm to determine if it is correct. Implementation phase 1. Code program translate the algorithm into a programming language 2. Test program manually check the program to determine if it is correct. Algorithm step by step instruction to solve a problem in a finite amount of time. Often written in pseudocode (pretend code). 4
Programming language A set of rules, symbols, and reserved words used to construct a program. Computer Languages - 1. Machine language (ex: 100101 01 : add 1) binary code - uses opcodes to represent possible instructions machine specific no translation required tedious to program in 2. Assembly Language (ex: ADD 01) Uses mnemonics to represent opcodes. machine specific translation required - assembler 3. High-level language Uses English like syntax & grammar to instruct computer operations Not machine specific - portable code translation required - compiler, interpreter Source Program A program written in a high level language Object Program The machine version of the source program Programming Language structures: 1. Sequence series of statements executed one after another 2. Selection statement execution is based on a condition 3. Repetition repeat execution of a group of statements based on a condition 4. Subprograms execute a group of statements when called Allows programs to be subdivided into subtasks. 5