Memory storage cards

•        A memory is a device that is used for storing data or information. It stores the instructions and data received from the input device.

•        A computer system consists of various types of memory devices to store instructions and data.

•        Memory components can be divided into three categories:

* Internal processor memory (built-in)

* Main or primary memory

* Secondary memory

Types of primary memory

•        Two categories:

*  RAM: Random Access Memory or Volatile memory

•        Requires power to hold data

•        Data in RAM has an address

•        CPU reads data using the address

•        CPU can read any address

* ROM: Read Only Memory or Nonvolatile memory

•        Holds data when power is off

•        Basic Input Output System (BIOS)

•        Power On Self Test (POST)

•        Another type is Flash memory

•        Data is stored using physical switches

•        Special form of nonvolatile memory

•        Camera cards, USB key chains

RAM

•        RAM:  Random Access Memory

* RAM is fast 

* Holds what’s currently being used

* Writable

* Virtually no speed penalty for accessing bits, no matter which location they’re in:  “random access”

* Typically 128 or 256 MB (and up to 1 GB) for personal computers

                  * Good idea:  buy as much as you can afford. 1 or 2 GB also available.

ROM

•        ROM (read-only memory)

* Contents pre-written and permanent programs called “firmware”

•        Stores bootstrap program.

•        Stores BIOS (Basic Input/Output System)

* Typically small:  <1 MB

* Some nonvolatile primary memory: 

•        PROM, EPROM, EEPROM,

Storage Concepts

•        Storage of data involves two operations

* Writing data

* Reading data

•        Storage media is the material on which data is stored

•        Storage devices are the hardware components that write data to, and read data from, storage media

Magnetic storage

•        Most common form of storage:  magnetic.

•        Magnetized spots on a surface, which may be

* on a tape,

*  on a disk,

                  * Hard disk, floppy disk, magnetic tape

Preparing Disks for Storage

           Formatting or initializing prepares disks for storage, magnetically mapping the disk’s surface.

Formatting Disks

•        Surface divided into:

* Main sections, called Track

Bits are stored within sectors along concentric circles called tracks

* Track subsections, called Sectors

* Groups of sectors, called Clusters

 

Magnetic storage

1. How a magnetic recording works:

         * A moving electrical charge (current) creates a magnetic field:

can be in one of two different orientations (polarities):

         * North-south (clockwise)

         * South-north (counter-clockwise) depending on the direction of the incoming current.

2. Use to magnetize an iron surface nearby.

Hard Disk Drive

Magnetic storage

1.     Head crash:

*  HDD has very fast spin rates

* R/W head floats above hard disk surface on tiny cushion of air

* R/W head can crash into disk surface if any impurity is there.

2.     To avoid contamination, platters are permanently sealed in the hard drive case.

Optical storage- Record & Read

How Disk Drives Works

1. laser sled (1)
2. sliding rails (2)
3. motor (3)
4. disc hub (4)
5. lens (5)
6. polycarbonate (6)
7. pits (7)
8. reflective material (8)
9. lacquer or other protective coating (9)
10. label surface (10)
11. lands (11)

Exampal 4 bit- 1GB

             4 bit = 1 Nibble

             8 bit = 1 byte

            1024 byte = 1 KB

            1024 KB = 1 MB

            1024 MB = 1 GB

Abbreviation

            KB = Kilo byte

            MB = Mege byte

            GB = Gega byte

Bigger Unites

            1 KB = 1024 Byte

            1 MB = 1024 KB = 1024 × 1024 Byte = 10,48,476 Byte

            1 GB =  1024 MB = 1024 × 1024 KB = 10,48,476 KB

    = 10,48,476 ×1024 Byte = 107,37,41,824 Byte