INTRODUCTION TO COMPUTING

1. INTRODUCTION TO COMPUTING Course Instructor: Asma Sanam Larik

2. PART I • What is Computer ? • What is Hardware ? • What is Software ? • What are the Input/ Output Devices ? • Von Neumann Architecture • CPU • Introduction to Memory

3. What is a Computer? • A Computer is a device that receives, stores, and processes information • Different types of computers have different characteristics • supercomputers: powerful but expensive; used for complex computations (e.g., weather forecasting, engineering design and modeling) • desktop computers: less powerful but affordable; used for a variety of user applications (e.g., email, Web browsing, document processing) • laptop computers: similar functionality to desktops, but mobile • palmtop computers: portable, but limited applications and screen size

4. Desktop Specifications • purchasing a computer can be confusing • sales materials contain highly technical information and computer jargon • the following specs describe two computer systems for sale in January, 2007 • Desktop 1 is a low-end system, inexpensive but with limited features • Desktop 2 is a high-end system, uses the latest technology so expensive

5. Hardware vs. Software • the term hardware refers to the physical components of a computer system • e.g., monitor, keyboard, mouse, hard drive • the term software refers to the programs that execute on the computer • e.g., word processing program, Web browser hardware components software components

6. Common Desktop Hardware

7. von Neumann Architecture • Although specific components may vary, virtually all modern computers have the same underlying structure • known as the von Neumann architecture • named after computer pioneer, John von Neumann, who popularized the design in the early 1950's • The von Neumann architecture identifies 3 essential components • Input/Output Devices (I/O) allow the user to interact with the computer • Memory stores information to be processed as well as programs (instructions specifying the steps necessary to complete specific tasks) • Central Processing Unit (CPU) carries out the instructions to process information

9. Central Processing Unit (CPU) • the CPU is the "brains" of the computer, responsible for controlling its inner workings • made of circuitry – electronic components wired together to control the flow of electrical signals • the circuitry is embedded in a small silicon chip, 1-2 inches square • despite its small size, the CPU is the most complex part of a computer (CPU circuitry can have 100's of millions of individual components) • commercial examples: Intel Core 2 Duo, AMD Athlon, Motorola PowerPC G4

10. CPU (cont.) • the CPU works by repeatedly fetching a program instruction from memory and executing that instruction • individual instructions are very simple (e.g., add two numbers, or copy this data) • complex behavior results from incredible speed • a 2.53 GHz Celeron D processor can execute 2.53 billion instructions per second • a 2.93 GHz Core 2 Duo processor can execute 2.93 billion instructions per second

11. Memory • memory is the part of the computer that stores data and programs • modern computers are digital devices, meaning they store and process information as binary digits(bits) • bits are commonly represented as either 0 or 1 • bits are the building block of digital memory by grouping bits together, large ranges of values can be represented

12. Memory (cont.) • modern computers use a combination of memory types, each with its own performance and cost characteristics • main memory (or primary memory) is fast and expensive • data is stored as electric signals in circuitry, used to store active data • memory is volatile – data is lost when the computer is turned off • examples: Random Access Memory (RAM), cache • secondary memory is slower but cheaper • use different technologies (magnetic signals on hard disk, reflective spots on CD) • memory is permanent – useful for storing long-term data • examples: hard disk, floppy disk, compact disk (CD), flash drive

13. Memory (cont.) • higher-end computers tend to have • more main memory to allow for quick access to more data and programs • more secondary memory to allow for storing more long-term data

14. Input/Output (I/O) • input devices allow the computer to receive data and instructions from external sources • examples: keyboard, mouse, track pad, microphone, scanner • output devices allow the computer to display or broadcast its results • examples: monitor, speaker, printer

15. Software • recall: hardware refers to the physical components of computers • software refers to the programs that execute on the hardware • a software program is a sequence of instructions for the computer (more specifically, for the CPU) to carry out in order to complete some task • e.g., word processing (Microsoft Word, Corel WordPerfect) • e.g., image processing (Adobe Photoshop, Macromedia Flash) • e.g., Web browsing (Internet Explorer, Mozilla Firefox)

16. Questions ???

17. PART II • What are bits and Bytes? • Boolean Operations • Flip Flop Gates • Organization of Main Memory • Hexadecimal Notation • Magnetic Disks and Tapes • Representation of Data, Sound , Text , Images

18. Bits and Bit Patterns • Bit: Binary Digit (0 or 1) • Bit Patterns are used to represent information. • Numbers • Text characters • Images • Sound • And others

19. Boolean Operations • Boolean Operation: An operation that manipulates one or more true/false values • Specific operations • AND • OR • XOR (exclusive or) • NOT

20. Figure 1.1 The Boolean operations AND, OR, and XOR (exclusive or)

21. Gates • Gate: A device that computes a Boolean operation • Often implemented as (small) electronic circuits • Provide the building blocks from which computers are constructed • VLSI (Very Large Scale Integration)

22. Figure 1.2 A pictorial representation of AND, OR, XOR, and NOT gates as well as their input and output values

23. Flip-flops • Flip-flop: A circuit built from gates that can store one bit. • One input line is used to set its stored value to 1 • One input line is used to set its stored value to 0 • While both input lines are 0, the most recently stored value is preserved

24. Figure 1.3 A simple flip-flop circuit

25. Figure 1.4 Setting the output of a flip-flop to 1

26. Figure 1.4 Setting the output of a flip-flop to 1 (continued)

27. Figure 1.4 Setting the output of a flip-flop to 1 (continued)

28. Figure 1.5 Another way of constructing a flip-flop

29. Hexadecimal Notation • Hexadecimal notation: A shorthand notation for long bit patterns • Divides a pattern into groups of four bits each • Represents each group by a single symbol • Example: 10100011 becomes A3

30. Figure 1.6 The hexadecimal coding system

31. Main Memory Cells • Cell: A unit of main memory (typically 8 bits which is one byte) • Most significant bit: the bit at the left (high-order) end of the conceptual row of bits in a memory cell • Least significant bit: the bit at the right (low-order) end of the conceptual row of bits in a memory cell

32. Figure 1.7 The organization of a byte-size memory cell

33. Main Memory Addresses • Address: A “name” that uniquely identifies one cell in the computer’s main memory • The names are actually numbers. • These numbers are assigned consecutively starting at zero. • Numbering the cells in this manner associates an order with the memory cells.

34. Figure 1.8 Memory cells arranged by address

35. Memory Terminology • Random Access Memory (RAM): Memory in which individual cells can be easily accessed in any order • Dynamic Memory (DRAM): RAM composed of volatile memory

36. Measuring Memory Capacity • Kilobyte: 210 bytes = 1024 bytes • Example: 3 KB = 3 times1024 bytes • Sometimes “kibi” rather than “kilo” • Megabyte: 220 bytes = 1,048,576 bytes • Example: 3 MB = 3 times 1,048,576 bytes • Sometimes “megi” rather than “mega” • Gigabyte: 230 bytes = 1,073,741,824 bytes • Example: 3 GB = 3 times 1,073,741,824 bytes • Sometimes “gigi” rather than “giga”

37. Mass Storage • On-line versus off-line • Typically larger than main memory • Typically less volatile than main memory • Typically slower than main memory

38. Mass Storage Systems • Magnetic Systems • Disk • Tape • Optical Systems • CD • DVD • Flash Drives

39. Figure 1.9 A magnetic disk storage system

40. Figure 1.10 Magnetic tape storage

41. Figure 1.11 CD storage

42. Files • File: A unit of data stored in mass storage system • Fields and keyfields • Physical record versus Logical record • Buffer: A memory area used for the temporary storage of data (usually as a step in transferring the data)

43. Figure 1.12 Logical records versus physical records on a disk

44. Representing Text • Each character (letter, punctuation, etc.) is assigned a unique bit pattern. • ASCII: Uses patterns of 7-bits to represent most symbols used in written English text • Unicode: Uses patterns of 16-bits to represent the major symbols used in languages world side • ISO standard: Uses patterns of 32-bits to represent most symbols used in languages world wide

45. Figure 1.13 The message “Hello.” in ASCII

46. Representing Numeric Values • Binary notation: Uses bits to represent a number in base two • Limitations of computer representations of numeric values • Overflow – occurs when a value is too big to be represented • Truncation – occurs when a value cannot be represented accurately

47. Representing Images • Bit map techniques • Pixel: short for “picture element” • RGB • Luminance and chrominance • Vector techniques • Scalable • TrueType and PostScript

48. Representing Sound • Sampling techniques • Used for high quality recordings • Records actual audio • MIDI • Used in music synthesizers • Records “musical score”

49. Figure 1.14 The sound wave represented by the sequence 0, 1.5, 2.0, 1.5, 2.0, 3.0, 4.0, 3.0, 0

50. Questions ???