Cs160 chapter 1
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  • 1. DATA STORAGEChapter 1
  • 2. 1.1 BITS AND THEIR STORAGEData Storage1-2
  • 3. BITS AND BIT PATTERNS Bit: Binary Digit (0 or 1) Bit Patterns are used to representinformation. Numbers Text characters Images Sound And others1-3
  • 4. BOOLEAN OPERATIONS Boolean Operation: An operation that manipulatesone or more true/false values Specific operations AND OR XOR (exclusive or) NOT1-4
  • 5. THE BOOLEAN OPERATIONS AND, OR, AND XOR(EXCLUSIVE OR)1-5
  • 6. GATES Gate: A device that computes a Boolean operation Often implemented as (small) electronic circuits Provide the building blocks from which computers areconstructed VLSI (Very Large Scale Integration)1-6
  • 7. A PICTORIAL REPRESENTATION OF AND, OR, XOR, AND NOTGATES AS WELL AS THEIR INPUT AND OUTPUT VALUES1-7
  • 8. 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 ispreserved1-8
  • 9. A SIMPLE FLIP-FLOP CIRCUIT1-9
  • 10. 1.2 MAIN MEMORYData Storage1-10
  • 11. MAIN MEMORY CELLS Cell: A unit of main memory (typically 8 bitswhich is one byte) Most significant bit: the bit at the left (high-order) endof the conceptual row of bits in a memory cell Least significant bit: the bit at the right (low-order) endof the conceptual row of bits in a memory cell1-11
  • 12. THE ORGANIZATION OF A BYTE-SIZE MEMORY CELL1-12
  • 13. MAIN MEMORY ADDRESSES Address: A “name” that uniquely identifiesone cell in the computer’s main memory The names are actually numbers. These numbers are assigned consecutively starting atzero. Numbering the cells in this manner associates an orderwith the memory cells.1-13
  • 14. MEMORY CELLS ARRANGED BY ADDRESS1-14
  • 15. 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”1-15
  • 16. 1.3 MASS STORAGEData Storage1-16
  • 17. MASS STORAGE On-line versus off-line Typically larger than main memory Typically less volatile than main memory Typically slower than main memory1-17
  • 18. MASS STORAGE SYSTEMS Magnetic Systems Disk Tape (all but obsolete) Optical Systems CD DVD Blu-Ray Flash Drives Solid State Drives (SSDs)1-18
  • 19. MAGNETIC DISKS1-19
  • 20. GAP BETWEEN HEAD AND PLATTER1-20HeadSmokeParticleHumanHairDustParticle
  • 21. DISK PERFORMANCE1-21DiskPerformanceSeek timeRotationallatencyTransferrate
  • 22. OPTICAL DISKS1-22
  • 23. CD AND DVD TRACK COMPARISON1-23CD DVD
  • 24. FILES A file is a named collection of bits Files are often stored in pieces 1 byte chunks in memory Sector-sized chunks on disk1-24
  • 25. 1.4 REPRESENTING INFORMATION AS BITPATTERNSData Storage1-26
  • 26. REPRESENTING TEXT Each character (letter, punctuation, etc.) isassigned a unique bit pattern ASCII American Standard Code for Information Interchange Uses patterns of 7-bits to represent most symbols used inwritten English text 128 (27) unique characters Unicode Uses patterns of 16-bits to represent the major symbols usedin languages world side 65,536 (216) possible characters ISO International Organization for Standardization 4,294,967,296 (232) possible characters1-27
  • 27. “HELLO.” IN ASCII1-28
  • 28. REPRESENTING NUMERIC VALUES Binary: a number system using only the digits 0(zero) and 1 (one) Maps well to the internal characteristics of thecomputer Limitations of computer representations of numericvalues Overflow: happens when a value is too big to berepresented Truncation: happens when a value is between tworepresentable values1-32
  • 29. REPRESENTING IMAGES1-33 Bit map techniques Pixel: short for “pictureelement” RGB Luminance andchrominance Vector techniques Scalable TrueType andPostScript
  • 30. SCALABLE VS. BITMAPPED FONTS1-34
  • 31. A SOUND WAVE REPRESENTED BY THE SEQUENCE 0,1.5, 2.0, 1.5, 2.0, 3.0, 4.0, 3.0, 01-35
  • 32. 1.5 THE BINARY SYSTEMData Storage1-36
  • 33. THE BASE TEN AND BINARY SYSTEMS1-37
  • 34. DECODING THE BINARY REPRESENTATION 1001011-38
  • 35. FINDING THE BINARY REPRESENTATION OF 131-39
  • 36. BINARY ADDITION1-40
  • 37. DECODING THE BINARY REPRESENTATION 101.1011-41
  • 38. 1-42There are 10 kinds of people inthe world: those who understandbinary and those who don’t.
  • 39. HEXADECIMAL NOTATION Hexadecimal notation: A shorthand notation for longbit patterns Divides a pattern into groups of four bits each Represents each group by a single symbol Example: 1010 0011 becomes A31-43
  • 40. THE HEXADECIMAL CODING SYSTEM1-44
  • 41. 1-45How many people can read hexif only you and DEAD peoplecan read hex? 57,006
  • 42. 1.6 STORING INTEGERSData Storage1-46
  • 43. STORING INTEGERS Two’s complement notation: The most popularmeans of representing integer values Excess notation: Another means of representinginteger values Both can suffer from overflow errors.1-47
  • 44. TWO’S COMPLEMENT1-48 Fixed number of bits MSB is sign bit 1 = negative 0 = positive
  • 45. ENCODING IN TWO’S COMPLEMENT NOTATION1-49
  • 46. ADDITION AND SUBTRACTION USING TWO’SCOMPLEMENT1-50
  • 47. TAKING ISSUE WITH THE BOOK“The point is that computerscan make mistakes.”-J. Glenn Brookshear, Computer Science, an Overview, p. 541-51
  • 48. WRONG
  • 49. TAKING ISSUE WITH THE BOOKComputers don’t makemistakes. They do exactlywhat you tell them to.1-61
  • 50. EXCESS NOTATION Another system of representing signed integers1. List all bit patterns of a given length2. Find the first bit pattern with a 1 in the MSB; this willrepresent zero3. Patterns below our zero represent negative number,patterns preceding it represent positive numbers1-62
  • 51. EXCESS EIGHT CONVERSION TABLE1-63
  • 52. 1.7 STORING FRACTIONSData Storage1-64
  • 53. STORING FRACTIONS Floating-point Notation: Consists of a sign bit, amantissa field, and an exponent field. Related topics include Normalized form Truncation errors1-65
  • 54. FLOATING-POINT NOTATION COMPONENTS1-66
  • 55. ENCODING THE VALUE 25⁄81-67