Partitioning the Hard Disk

                                              Partitioning the Hard Disk

                 As described in the previous section, a disk must be physically formatted (low-level format), partitioned, and logically formatted (high-level format) before it can store data. The partitioning phase creates physical divisions of the disk that can be used to segment the disk and allow for two or more operating systems or the creation of multiple file systems.

Partitioning the hard disk allows you to:

• Divide the disk into logical "sub-drives" that can be addressed separately with a drive letter assigned to each, such as C:,D:, and E:
• Create separate areas on the disk for multiple operating systems, such as storing Windows and Linux on the same hard disk, each in its own partition.
• Separate program files from data files on separate disk partitions to facilitate faster and easier data backups. 

           Partitioning a hard disk can improve the disk's efficiency. For example, windows assigns                      disk clusters (logical collections of sectors) that are sized in proportion to partition size. Bigger            clusters may sound like a good thing, but just the opposite is true. Large disk drives or bigger              partitions result in bigger clusters, which unfortunately result in small unused spaces on the                 disk. By reducing the size of the disk or more smaller partitions, the result is reduced clusters                sizes.                          

                   If you wish to have only one partition on your disk, that's perfectly all right. However,                  you should know that on some systems, if you wish to use the entire  disk, you will have                      to create smaller partitions. For example, on DOS, Windows 3x, or an early release of                         Windows 95, partition sizes must be smaller than 2GB, which means that a disk larger than 2               GB  must be divided into two or more partitions if you wish to us the entire disk. Windows 98             and Windows 2000 allow you to create partitions of up to 4TB (terabytes).

                A hard disk can be divided into two types of partitions:

• Primary partitions: the primary partition contains the operating system and is usually the one from which the  PC is booted. A hard disk can be divided into a maximum of four primary partitions, but on most operating systems, only one primary partition may be active at a time.

• Extended Partitions: this type of partition can be divided into as may as 23 logical partitions, each of which can be assigned its own drive identity. Extended petitions can be used for any purpose.

Hard Disk Construction

                                              Hard Disk Construction

                 There are many different types and styles of hard disks on the market, all of which have roughly the same physical components. The differences among th different drive styles and types are usually in the components-the materials used and the way they are put togeter. But essentially one disk drive operates like all others. the major components in typical hard disk drive are as follows:

• Disk platters
• spindle and spindle motor
• Read/write heads
• Head actuators
• Air filter
• Logic board 
• Connectors and jumpers
• Bezel

         On this list, only the connectors and jumpers are accessible outside of the enclosure that houses all of the other components of the disk drive. The metal case and the components it encloses form what is called the Hard Disk assembly (HDA). The HDA is a sealed unit that is never opened. The following sections provide and overview of each of the hard disk's components.

Hard Disk Drives

                                                          Hard Disk Drives

              The hard disk is hardly a personal computer invention. The first hard disks, which first showed up in the 1950s on mainframe computers, were 20 inches in diameter and held only a few megabytes of data. Hard disks were originally called "fixed disks" and "Winchester drives" and became known as hard disks later to differentiate them from floppy disks. However, the basic technology used in the earliest hard disks has not changed all that much over the years, although the size and capacity of the drives has.

               It is the main storage device. It consists of all of the computer's item as well as documents created by using all software. It lies inside the system Board (CPU Box). Technically microcomputer hard disks are called or fixed disks, as they are a pack of disks permanently sealed inside a disk drive.

              The sealed case contains platters fixed in place, read/write heads and other part of mechanisms. It over-comes much of the danger of dust, magnetism and fingerprints interfering with the data. the read/write heads do not actually touch the surface of the disk (as floppy disk drives) but fly over it on a cushion of air.

Network Structures

                                                        Network Structures

                As indicated above, creating a network can be as simple as connecting two PCs together or connecting together thousands, even millions, or other networks. Depending on the needs of the users, a network can be quite simple or it can be very complex. There are two basic network structures:

Peer-to-peer (peer-based) networks

                 Two or more computers directly connected to one another for the sole purpose of directly sharing data and hardware resources. In the below figure, Ram and Shyam are directly connected by a cable and are able to grant permission to each other to open and use files and programs stored on their PCs and to share CD-ROM drives, printers, and other hardware. On a peer-based network, each user is responsible for the security and access of his or her PC because there is no central administrator. A peer-to-peer network is practically limited to not more than ten PCs arranged as a LAN.

Server-based (client/server) networks 

                   A network of connected computers and peripherals with a centralized server that facilitates the sharing of network data, software, and hardware resources. A client/server network typically has a central administrator that manages the permissions and access to the resources of the network. This structure is used for the majority of LANs and virtually all WANs and other network types that connect over a WAN. Any computer that requests services, such as a file, a program, or printing from the network is a client, and any computer that services the requests made to the network is a server. Depending on the request, any computer on the network can be a client for one type of request and a server for another. On a larger network, centralized computers process a variety of services for the computers connected to the network. Typically, on larger networks clients are clients and servers are servers.