Essentials of informatics

Transcription

1 Essentials of informatics Computer hardware and software Mgr. Markéta Trnečková, Ph.D. Palacký University, Olomouc

2 Introduction Computer science computer design, computer programming, information processing, algorithmic solutions of problems, and the algorithmic process Algorithm steps that define how a task is performed Program a representation of an algorithm Programming process of developing a program, encoding it in machine-compatible form, and inserting it into a machine Software programs, and the algorithms they represent Hardware the machinery itself Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 1 / 53

3 Euclidean algorithm for finding the greatest common divisor of two positive integers Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 2 / 53

4 Algorithm more algorithms providing same task time complexity average number of steps Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 3 / 53

5 Algorithm algorithm for performing a task has been found the performance of that task no longer requires an understanding of the principles on which the algorithm is based the performance of the task is reduced to the process of merely following directions the intelligence is encoded in the algorithm the level of intelligence displayed by machines is limited by the intelligence that can be conveyed through algorithms we can construct a machine to perform a task only if an algorithm exists for performing that task no algorithm exists for solving a problem the solution of that problem lies beyond the capabilities of machines incompleteness theorem (1930s Kurt Gödel) there are problems that can not be solved by algorithm Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 4 / 53

6 Halting problem The halting problem is the problem of determining, from a description of an arbitrary computer program and an input, whether the program will finish running (i.e., halt) or continue to run forever. Alan Turing (in 1936) general algorithm to solve the halting problem for all possible program-input pairs cannot exist Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 5 / 53

7 Bits information is encoded as patterns of 0s and 1s (bit short for binary digits) nibble = 4 bits byte = 8 bits size of memory cell kilobyte = 1024 bytes (210 ) megabyte = 1000 kilobytes gigabyte = 1000 megabytes terabyte = 1000 gigabytes Mgr. Marke ta Trnec kova, Ph.D. (UPOL) Essentials of informatics 6 / 53

8 Binary notation information is encoded as patterns of 0s and 1s Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 7 / 53

9 Data Storage bits are only symbols whose meaning depends on the application patterns of bits numeric values, characters in an alphabet and punctuation marks, images, sounds,... manipulation with bits via Boolean operation 1 = true; 0 = false operations AND, OR, XOR and NOT Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 8 / 53

10 AND x AND y e.g. Today is Thursday AND it is afternoon Inputs represent the truth or falseness of the compound statement s components Output represents the truth or falseness of the compound statement true only when both of its components are true Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 9 / 53

11 OR x OR y e.g. Today is Thursday OR Friday true only when at least one of its components is true Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 10 / 53

12 XOR exclusive or x XOR y either x or y but not both true when one of its inputs is true and the other is false Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 11 / 53

13 NOT NOT x true when input is false Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 12 / 53

14 Gate Gate a device that produces the output of a Boolean operation Constructed as gears, relays, optic devices,... Inside today s computers small electronic circuits in which the digits 0 and 1 are represented as voltage levels Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 13 / 53

15 Flip-flop circuit Gates the building blocks circuit Example Flip-flop circuit Fundamental unit of computer memory Produced output (0 or 1) remains constant until a pulse causes it to shift to the other value placing 1 on the upper input output 1 placing 1 on the lower input output 0 Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 14 / 53

16 Hexadecimal notation information string of bits quite long long strings stream simplification hexadecimal notation why? bit patterns multiples of four single symbol = four bits e.g B5 Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 15 / 53

17 Text as bit pattern symbol in the text a unique bit pattern In the 1940s and 1950s American National Standards Institute (ANSI) the American Standard Code for Information Interchange (ASCII) bit patterns of length seven the upper- and lowercase letters of the English alphabet, punctuation symbols, the digits 0 through 9, and certain control information such as line feeds, carriage returns, and tabs ASCII is extended to an eight-bit-per-symbol format by adding a 0 at the most significant end of each of the seven-bit patterns Code each pattern fits conveniently into a typical byte-size memory cell and provides 128 additional bit patterns that can be used to represent symbols beyond the English alphabet Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 16 / 53

18 Text as bit pattern International Organization for Standardization (also known as ISO) number of extensions to ASCII, each of which was designed to accommodate a major language group Problems: the number of extra bit patterns available in extended ASCII is simply insufficient to accommodate the alphabet of many Asian and some Eastern European languages documents containing text of languages from disparate language groups could not be supported Unicode was developed Code unique pattern of up to 21 bits to represent each symbol Combination Unicode character set and the Unicode Transformation Format 8-bit (UTF-8) encoding standard the original ASCII characters can still be represented with 8 bits, while the thousands of additional characters can be represented by 16 bits Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 17 / 53

19 Numbers as bit pattern storing numbers as text inefficient e.g. value 25: 16 bits using ASCII (the largest number we could store using 16 bits is 99) using binary notation we can store any integer in the range from 0 to in 16 bits two s complement notation storing whole numbers (negative numbers as well as positive) floating-point notation numbers with fractional parts such as 1/2 or 3/4 Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 18 / 53

20 Two s complement notation Fixed number of bits The leftmost bit of a bit pattern indicates the sign of the value sign bit Negative values sign bits are 1 Non-negative values sign bits are 0 Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 19 / 53

21 Floating-point notation High-order bit the sign bit Divide the remaining 7 bits of the byte into two groups exponent field mantissa field e.g. 3 bits exponent field, 4 bits mantissa field Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 20 / 53

22 Floating-point notation bit pattern; sign bit = 0, exponent = 110, mantissa = 1011 first extract the mantissa and place a radix point on its left side.1011 extract the exponent 110 and interpret as signed integer move the radix in our solution to the right by 2 bits = Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 21 / 53

23 Images as bit pattern image = a collection of dots (pixel picture element) each pixel is encoded entire image a collection of these encoded pixels (bit map) method of encoding depends on applications black-and-white images 1 bit gray-scale images 8 bits color images RGB encoding (3 x 8 bits) image = a collection of geometric structures (lines, curves,... ) encoded using techniques of analytic geometry Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 22 / 53

24 Sound as bit pattern sample the amplitude of the sound wave at regular intervals each sample 16 bits Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 23 / 53

25 Data and programming programming language simplified language which computers understand int euclid_gcd ( int a, int b) { if (a >= b) { int dividend = a; int divisor = b; } else { int dividend = b; int divisor = a; } while ( divisor!= 0) { int remainder = dividend % divisor ; dividend = divisor ; divisor = remainder ; } return dividend ; } Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 24 / 53

26 History Abacus consisting of beads strung on rods that are in turn mounted in a rectangular frame Abacus a data storage system Complete computational machine combined with a human Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 25 / 53

27 History Technology of gears Blaise Pascal ( ), Gottfried Wilhelm Leibniz ( ), Charles Babbage ( ) data = gear positioning Output (Pascal s and Leibniz s machines) = final gear positions Output (Babbage s machine) = print results on paper Pascal s machine addition Leibniz s machine variety of arithmetic operations Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 26 / 53

28 History Babbage s Difference Engine could be modified to perform a variety of calculations Babbage s Analytical Engine (never constructed) read instructions in the form of holes in paper cards Augusta Ada Byron (Ada Lovelace) world s first programmer Holes in paper (Joseph Jacquard, ) a weaving loom Herman Hollerith ( ) applied the concept of representing information as holes in paper cards Punched cards until 1970s Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 27 / 53

29 History In the early 1900s advances in electronics (electronically controlled mechanical relays) Electromechanical machine of George Stibitz (1940 Bell Laboratories) Mark I (1944 Harvard University) Technology of vacuum tubes totally electronic computers Atanasoff-Berry machine ( ) Colossus decode German messages World War II ENIAC (electronic numerical integrator and calculator) Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 28 / 53

30 History Transistors and integrated circuits (complete circuits constructed as single units) smaller computers The processing power of computing machines began to double every two years Chips integrated circuits encased in blocks of plastic desktop computers (homemade computers from combinations of chips) 1976 commercial computer (Apple Computer, Inc.) 1981 first desktop computer (IBM) (personal computer or PC) Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 29 / 53

31 History 20th century connect computers (Internet) World Wide Web system by which documents stored on computers are linked together Search engines Miniaturization of computing machines small computers running GPS, monitoring the function of the engine,... Smartphones Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 30 / 53

32 Computers Microcomputer microprocessor chip as its central processing unit (CPU) personal computers designed to be used by a single person at any given time desktop PC, laptop PC, smartphones, tablets,... Minicomputer midrange computers multi-user machines bigger processing power Mainframes large, powerful computers capable of handling processing requests for large numbers of users simultaneously used in large organisations governments and banks users would connect to a mainframe using a terminal Supercomputers like mainframe computers processing big data Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 31 / 53

33 Computer hardware Physical devices that make up a computer Processing Devices hardware which are involved in processing data central processing unit (CPU) and graphics processing unit (GPU) part of the motherboard the central circuit board that holds these devices along with other devices Memory Devices store data very fast and expensive memories are used by CPU and programs, not by user I/O or Input/Output Devices input take input from user keyboard, mouse, microphone,... output output result to user monitor, printer, speaker,... Storage Devices keep data when the computer is turned off store data both by a program and an user optical disks, flash drives Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 32 / 53

34 Motherboard Mainboard Provides electrical connection between all computer components Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 33 / 53

35 Main memory Large collection of circuits (such as flip-flops) Each stores a single bit Cell manageable unit, size byte (8 bits) High-order end (left), low-order end (right) The most significant bit (high-order bit), the least significant bit (low-order bit) Address unique name each cell Cells can be accessed independently as required (access cells in any order) Random access memory (RAM) Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 34 / 53

36 Mass storage Main memory volatile, limited size Mass storage (or secondary storage) less volatility, large storage capacities,low cost, ability to remove the storage medium from the machine some of them require mechanical motion slower, more prone to mechanical failures Magnetic system Optical system Flash drives Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 35 / 53

37 Magnetic system Magnetic disk or hard disk drive (HDD) Thin spinning disk with magnetic coating Read/write heads placed above and/or below the disk As the disk spins head traverses a circle track Disk storage system consists of several disks mounted on a common spindle (one on top of the other) cylinders Track is divided into small arcs sectors Sectors contain the same number of bits (track contains the same number of sectors) High-capacity disk capable of containing different number of sectors Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 36 / 53

38 Optical systems Compact disk (CD) 12 centimeters in diameter, consist of reflective material covered with a clear protective coating Information recorded on them by creating variations in their reflective surfaces Retrieving information by means of a laser that detects irregularities on the reflective surface of the CD as it spins DVDs (Digital Versatile Disks) multiple, semitransparent layers that serve as distinct surfaces when viewed by a precisely focused laser BDs (Blu-ray Disks) laser in the blue-violet spectrum (is able to focus its laser beam with very fine precision) Provides over five times the capacity of a DVD Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 37 / 53

39 Flash drives magnetic and optical system physical motion, slow compared to the speed of electronic circuitry Flash memory technology bits are stored by sending electronic signals directly to the storage medium where they cause electrons to be trapped in tiny chambers of silicon dioxide, thus altering the characteristics of small electronic circuits Hold their captive electrons for many years without external power Repeated erasing slowly damages the silicon dioxide chambers Flash drives they are not as reliable as optical disks for truly long-term applications SSDs (solid-state disks) large flash memory devices, designed to take the place of magnetic hard disks SSDs better resilience to vibrations and physical shock, quiet operation and lower access times more expensive than hard disks, more limited lifetime SD (Secure Digital) memory cards plastic rigged wafer about the size a postage stamp, also mini and micro sizes SDHC (High Capacity) up to 32 GBs SDXC (Extended Capacity) memory cards more than 1TB Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 38 / 53

40 CPU Central processing unit (CPU) or processor circuitry in a computer that controls the manipulation of data small flat squares (approximately two inches by two inches) whose connecting pins plug into a socket mounted on computer s motherboard Microprocessors smaller, used in smartphones, mini-notebooks,... CPU consists of three parts: arithmetic/logic unit circuitry that performs operations on data control unit circuitry for coordinating the machine s activities register unit data storage cells registers temporary store information within the CPU CPU and main memory are connected by a collection of wires called a bus Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 39 / 53

41 Controllers Controller communication between a computer and other devices Circuit permanently mounted on the computer s motherboard Circuit board that plugs into a slot on the motherboard Connection via cables or connector, called a port Translates messages and data between the computer and peripheral device Originally, each controller was designed for a particular type of device Recently, universal serial bus (USB) and FireWire Each controller communicates with the computer itself by means of connections to the same bus that connects the computer s CPU and main memory Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 40 / 53

42 USB USB Intel Lower cost Mice, keyboards, printers, scanners, digital cameras, smartphones, and mass storage systems Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 41 / 53

43 FireWire FireWire Apple 4-conductor and 6-conductor Faster transfer rate Video recorders and online mass storage systems Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 42 / 53

44 Peripheral devices Computer monitor displays images generated by a computer TFT-LCD (Thin Film Transistor Liquid Crystal Display) CRT (Cathode Ray Tube) Keyboards Computer mouses Printers Toner-based printers (laser), inkjet printers, dye-sublimation printers, thermal printers Scanners External storage devices (e.g. USB flash drives) Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 43 / 53

45 Software Software a program (e.g. operating system, application) running on a computer Computer hardware provides a physical devices required to run (and also store) computer software Types: system software manages and controls computer hardware operating systems software that controls the operation of a computer programming software tools that software developers use to create, debug, and maintain other software application software perform productive tasks for users Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 44 / 53

46 Operating systems Software that controls the overall operation of a computer Provides the interface by which a user can request the execution of programs Best known example of an operating system Windows UNIX core Mac OS and Linux Casual computer users the differences between operating systems are largely cosmetic Computing professionals major changes in the tools they work with or the philosophy they follow in disseminating and maintaining their work Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 45 / 53

47 Mac OS X, Windows, and Linux Windows User friendly, an extensive collection of software and broad hardware support Closed source, some of the biggest computer headaches malware, viruses,... Mac OS Lot safer Mac OS doesn t get the Windows viruses Usage restrictions in its license can only be run on systems constructed by Apple Linux Major downside of this OS is its price Vast collection of Linux distributions Little resource requirements OS is open-source any user around the world can examine Linux source code Disadvantage lack of user-friendliness Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 46 / 53

48 Components of an operating system User interface communication with users through textual messages shells graphical user interface (GUI) files and programs, are represented as icons Window manager component within today s GUI Kernel internal part of an operating system Contains software components that perform the very basic functions required by the computer installation File manager coordinates the use of the machine s mass storage Device drivers software units that communicate with the controllers Memory manager coordinate the machine s use of main memory Scheduler and dispatcher in a multiprogramming system the scheduler determines which activities are to be considered for execution, and the dispatcher controls the allocation of time to these activities Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 47 / 53

49 Another dividing of software Freeware software for free Payware opposite to freeware Shareware provided to users without payment and is often limited by any combination of functionality, availability or convenience Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 48 / 53

50 Computer network Computer network - set of computer connected together main goal share resources computers = nodes connection wired or wireless Internet global system, internet protocol (IP) network IP address numerical label (IP v. 4, IP v. 6) Domain name system (DNS) hierarchical decentralized naming system Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 49 / 53

51 Wired connection Coaxial cable local area networks transmission speed: from 200 million bits per second to more than 500 million bits per second Twisted pair cabling used for wired Ethernet and other standards transmission speed: from 2 Mbit/s to 10 Gbit/s Optical fiber low transmission loss and immunity from electrical interference can be used for long runs of cable carrying very high data rates Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 50 / 53

52 Wireless technology Terrestrial microwave Communications satellites Cellular and PCS systems Radio and spread spectrum technologies Wi-Fi Bluetooth exchanging data over short distances Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 51 / 53

53 Exercises 1 Describe the algorithm for cooking eggs. 2 Convert the following binary representation to its equivalent base 10 form: Convert the following base 10 representation to its equivalent binary form: Determine the output of the following circuit, assuming that the upper input is 1 and the lower input is 0. What would be the output when upper input is 0 and the lower input is 1? 5 Use hexadecimal notation to represent the following bit pattern: What bit pattern is represented by the following hexadecimal pattern? ABCD 7 What is the largest numeric value that could be represented with three bytes if each digit were encoded using one ASCII pattern per byte? What if binary notation were used? 8 Suppose the robot knows the turn left and step instructions. How does the turn right program look like? Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 52 / 53

54 Exercises 9 Suppose you want to interchange the values stored in memory cells 2 and 3. What is wrong with the following sequence of steps: Step 1. Move the contents of cell number 2 to cell number 3. Step 2. Move the contents of cell number 3 to cell number 2. Design a sequence of steps that correctly interchanges the contents of these cells. 10 What advantage do flash drives have over the other mass storage systems introduced? 11 List four activities of a typical operating system. Mgr. Markéta Trnečková, Ph.D. (UPOL) Essentials of informatics 53 / 53