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DATA STORAGE

DATA STORAGE. OBJECTIVE. At the end of this session the students should be able to: Define the terms Primary and Secondary storage Differentiate between Primary and Secondary Storage Illustrate how data flows between primary and secondary storage. KEY WORDS. Primary storage

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DATA STORAGE

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  1. DATA STORAGE

  2. OBJECTIVE At the end of this session the students should be able to: • Define the terms Primary and Secondary storage • Differentiate between Primary and Secondary Storage • Illustrate how data flows between primary and secondary storage

  3. KEY WORDS • Primary storage • Secondary storage • Immediate Access Store/Internal Memory • Auxilliary/Backing Storage/External Memory

  4. Can you identify the main classifications of Storage?

  5. HERE’S The Answer! • Storage has been divided into: • Primary storage: Data that is currently being used is held in Main Memory. • Primary storage is also referred to as Immediate Access Store (IMAS)/Internal memory. - Secondary storage: also known as Auxillary or Backing storage/ External Memory, holds data permanently for later use.

  6. Home-Work • The company Sarah works for is interested in purchasing storage for her computer. She has to save data on a daily basis and the cost of storage must be affordable. (A) What type of storage will you recommend? (B) Give ONE advantage of primary storage over secondary storage (C) List Two other terms that are used to refer to primary storage and two terms that are used to refer to secondary storage. 2. What are the TWO main components of primary storage? 3. What is the function of the TWO components? IT PORTFOLIO Produce a table in MS Word 2007 to show the differences between Primary Storage and Secondary Storage w.r.t. Capacity, Cost, Function, Portability and Speed

  7. OBJECTIVES The student should be able to: • State the main components of primary storage. • Explain the function of RAM and ROM • Explain the difference between RAM and ROM

  8. Primary Storage comprises of: • RAM (Random Access Memory) • ROM (Read Only Memory) To see a photo of a RAM chip: http://community.webshots.com/photo/fullsize/2175072340017373952vtTXtM

  9. RAM & ROM CHIPS ROM CHIP RAM memory module

  10. CAN YOU IDENTIFY AT LEAST TWO DIFFERENCES BETWEEN RAM & ROM???

  11. RANDOM ACCESS MEMORY (RAM) • RAM is immediately available to the processor and • holds data and instructions temporarily, while • processing takes place. • RAM is volatile meaning the data can be changed and all information is lost when the computer is switched off. HOW IS RAM DIFFERENT FROM ROM??

  12. READ ONLY MEMORY (ROM) • ROM chips hold programs (data and instructions) necessary for starting the computer when it is switched on. • The information is fixed at the time of manufacture. • ROM is non-volatile- information stored on ROM is permanent and cannot be deleted but can only be accessed or read. Its main use lies in the distribution of software (that doesn’t need frequent updating).

  13. STUDENT ACTIVITY Use the terms to draw a diagram that show how data flows in the computer. Explain how the data flows. INPUT DEVICE RAM OUTPUT DEVICE CPU ROM SECONDARY STORAGE

  14. Flow of data in a Computer System CPU INPUTDEVICE data info OUTPUT DEVICE RAM ROM Primary Storage BACKING STORAGE/SECONDARY STORAGE

  15. How data Flows in the Computer • Data is sent to RAM via an input device • The data is sent from RAM to the CPU to be processed • The processed data (information) is sent back to RAM from the CPU • The processed data is sent from RAM to an output device to be displayed • The data is sent to backing storage for later use.

  16. OBJECTIVES At the end of this session the students should be able to: • State the types of ROM chips • State how each ROM chip is different from each other or similar to each other

  17. There different types of ROM chips: • PROM (Programmable Read Only Memory) - has no data locked into it upon manufacture but data can be locked in place, so that the memory can no longer be changed. Thus, data can be written once after manufacture. • EPROM (Erasable Programmable Read Only Memory) - gets its original data in the same way as the PROM chip does. However, the data can be erased several times using ultra-violet light. • EEPROM (Electrically Erasable Programmable Read Only Memory)- a special type of ROM chip that can be erased several times by the user by exposing the chip to an electrical charge.

  18. A similarity amongst all three ROM chips is they are used in: Read-Only Mode! Picture of a PROM chip

  19. OBJECTIVES At the end of this session the students should be able to: • Explain why a computer represents data in the form of binary • Explain the terms related to data storage: bit, byte, character, word • Calculate the number of bits and bytes in a word/s • State the different units of storage

  20. Why the computer stores data • For processing • Temporarily • using Random Access Memory (RAM) • For later use • permanently • using secondary storage Computers do not store data the way we see it, but in the form of binary digits

  21. Why binary digits? • The computer is an electronic device • The computer is a digital device • Electronic • the computer uses electricity to work • Digital • the use of binary digits to store data

  22. HOW IS DATA STORED? • A computer’s memory is made up of bi-stable devices (two-state) meaning these components can be set in one of two states, represented by a 0 or 1 (called a binary digit). A bit is the smallest unit of storage in a computer. • A byte is made up of 8 bits which is one character (letter, digit, symbol and even a space)

  23. WHAT’S GOING ON?? Hi! Huh??

  24. 01000001 A So if a byte is the amount of storage needed to store one character then a computer with 32,000 bytes of memory will be able to store up to 32,000 characters!

  25. QUESTIONS?? How many bytes are in the following? • Hi! • Have fun! • A • 9 How many bits are in the following? • Hi! • Have fun! • A • 9

  26. HOW IS DATA STORED? Location: a unit of storage space in a computer's main memory Address: A number that is assigned to each location in a computer’s memory Word: a fixed-sized group of bits that are handled together by the machine. Word size: The number of bits (in a word)

  27. UNITS OF STORAGE:MEANING OF ACRONYMS • BIT- BINARY DIGIT ( 1 or a 0) • KB- KILOBYTE • MB-MEGABYTE • GB- GIGABYTE • TB- TERABYTE

  28. UNITS OF STORAGE • 1 CHARACTER = 1 BYTE = 8 BITS • 1KB= 1024 BYTES • 1MB= 1024KB • 1GB= 1024MB • 1TB= 1024GB

  29. HOW IS DATA MEASURED? Can you complete the table below? UNITS OF STORAGE • 1 GB= • 1 byte = • 1 MB = • 1 TB = • 1 character = • 1 KB = ANSWER 1 byte (1 character) = 8bits 1 KB = 1024 bytes 1 MB = 1024 KB 1 GB = 1024 MB 1 TB = 1024 GB

  30. AFL

  31. …Secondary Storage…

  32. What is the difference between a storage medium & storage device? The Storage Medium is the actual material object used for storing the data. Some examples are… • FLOPPY DISK • HARD DISK • MAGNETIC TAPE • CD • DVD • CASSETTE

  33. Storage DEVICE The Storage Device is the equipment that handles the use of the medium. For example… • FLOPPY DISK DRIVE • HARD DISK DRIVE • MAGNETIC TAPE DRIVE • CD-ROM DRIVE • DVD DRIVE • CASSETTE RECORDER/PLAYER

  34. CLASSIFICATION OF STORAGE MEDIA Storage media can be classified based on: • How the data is stored OR • How the data is accessed

  35. HOW DATA IS STORED Data can be stored using one of the following methods: • Magnetic • Optical • Electrical

  36. TYPES OF ACCESS TO DATA Storage Media can offer either: • Serial Access or • Direct Access to data

  37. DIRECT ACCESS • A method for retrieving or storing data in which the data (record) is identified by the position of the record in the file. The record is accessed directly (non-sequentially). Direct Access is also called Random Access.

  38. SERIAL ACCESS • Serial Access is where the records are accessed in the order it was stored. Hence, records are stored in sequential order and the search for a record is conducted from the beginning of the file until the desired record is reached.

  39. SECONDARY STORAGE:MAGNETIC MEDIA Types of Magnetic Media: • Hard disk • Floppy disk • Magnetic Tape • Cassette MAGNETIC DISK

  40. TYPE OF ACCESS

  41. MAGNETIC DISK • The data is laid out on concentric tracks on the surface of a flat disk. Data is stored as magnetized spots on the surface of the disk.

  42. WHAT ARE THE PARTS OF A MAGNETIC DISK??? SECTORS Magnetic disks are formatted into 3 areas: TRACKS • What is a: • Sector • Track • Cylinder CYLINDERS

  43. A Hard Disk Layout

  44. A schematic picture of a hard disk.

  45. MAGNETIC TAPE • A recording medium consisting of a thin tape with a coating of a fine magnetic material, used for recording analogue or digital data. Data is stored in frames across the width of the tape. The frames are grouped into blocks or records which are separated from other blocks by gaps.

  46. MAGNETIC TAPE • Magnetic tape is a serial access medium, similar to an audio cassette, and so data (like the songs on a music tape) cannot be quickly located. • However large amounts of information can be stored within magnetic tape. Due to this fact, magnetic tapes are used for the regular backing up of hard disks

  47. QUESTION?? • Draw a diagram of a floppy disk and a hard disk showing how data is stored • What do we mean when we say we are formatting a disk? • State TWO differences and Two similarities between floppy diskettes and hard disk. • State ONE similarity and ONE difference between magnetic tape and magnetic disks.

  48. OPTICAL MEDIA • CD-ROM • CD-R • CD-RW • DVD • Blu-Ray

  49. OPTICAL MEDIA • A spiral track is molded onto one side of this disc with tiny indentations, which are called pits. • In a DVD/CD drive the information is read by focusing a laser beam on this spiral track, and scanning along the track at a constant speed. Because the pits scatter some of the reflected light from the laser, the returning laser beam will have a reduced intensity whenever it encounters a pit. When the laser light is converted into an electrical signal, the drive can interpret the pattern of pits as binary information; ones and zeros.

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