The primary memory of every computer is essentially magnetic memory?

No, Primary memory of modern computers are essentially semiconductor memories.

L1 cache is a split memory to speed up execution?

Yes, L1 cache works based on principle of locality of reference and is used for increasing speed of execution.

Modem as well as Ethernet Card are essential to provide Data One Broadband Connection?

Yes, modem and ethernet are required to translate signals from computer to a form that is acceptable by broadband connection and vice-versa.

C++ compiler cannot handle scanf and printf commands as available in C?

No, by including stadio.h header file we can handle scanf and printf commands available in C.

Microsoft windows 2000 is a single user operating system.

Yes, only one user can login and work with windows 2000 OS. Multiple windows can be opened and multiple programs can be executed on time sharing basis.

Pentium is a 64 bit machine since it has got 64 bit Data Bus?

Yes, It has 64 bit data bus and internal processing capability.

What are the different forms of secondary storage media employed in modern day computer systems?

Various secondary storage devices are classified into two categories
1. Detachable storage devices
2. Fixed storage devices

Detachable storage devices can be easily removed and can be inserted latter when needed. Some examples of detachable storage devices are Floppy disk, CD, DVD etc. Floppy disk is magnetic storage device where data is stored in concentric tracks of magnetic material in a plastic disk. They are used to store small amount of data (upto 1.44 MB). They can be easily inserted and can be easily removed.
Another storage device in CD (Compact Disk) and DVD (Digital Video Disk). They can be used to store large volume of data. A typical CD can store 700 Megabyte data and a DVD can store 8 Giga bytes to 16 Giga Byte data. They are used to store audio and video data as well as general data. Tapes are also detachable storage devices. They are basically sequential storage devices. They can be used for storing backup data and for on-line recording of transactions for future reference or for transaction processing system. They have magnetic based read/write mechanism.
One of the most popular secondary storage device is hard disk. Hard disk contains a stack of platters in which data is stored in concentric circular tracks. They are used in almost every computer. They are used to store the operating systems and files that are frequently used. Hard disks are not generally removed from computer. Currently small hard disks of 160 Giga bytes that can be externally connected through USB ports are available.
Another secondary memory device that is gaining popularity is pen drives. They are basically EPROM (Erasable and Programmable Read Only Memory) based memory. They are also called flash memory. They can be connected through the USB port of computer and can store upto 8 GB of data. They can be easily detached and carried in pocket. They can be used to store any type of data.

What is Physical Layer?

The physical layer is responsible for encoding and transmission of data over network communications media. It operates with data in the form of bits that are sent from the physical layer of the sending (source) device and received at the physical layer of the destination device. Ethernet, Token Ring, SCSI, hubs, repeaters, cables and connectors are standard network devices that function at the physical layer. The physical layer is also considered the domain of many hardware related network design issues such as LAN, WAN topologies and wireless technology.
Normally the application programmers and users use layer 5 protocols (application layer. Layer 3 and 4 protocols are services provided by the TCP/IP stack in operating system. Microcontroller firmware in the network adapter handles layer 2 issues. It is supported by driver software in the operating system. Non-programmable analog and digital electronics are normally in charge of the physical layer typically using an application specific integrated circuit (ASIC) chipset for each radio interface or other physical standards.

What is Data Link Layer?

Data Link Layer is used to move packets from the network layer on two different hosts. The process of transmitting packets on a given link layer and receiving packets from a given layer can be controlled both in the software device driver for the network card as well as on firmware or specialist chip sets. These will perform data link functions such as adding a packet header to prepare it for transmission, and then actually transmit the frame over a physical medium. For Internet access over a dial up model, IP packets are usually transmitted using PPP (Point to Point Protocol). For broadband Internet access such ADSL or cable modem PPPoE is used. On a local wired network, Ethernet is usually used and on wireless network IEEE 802.11 is usually used. For wide area network either PPP over T-Carrier or E-Carrier lines, Frames relay, ATM or packet over SONET/SDH (POS) is often used. The link layer can also be the layer where packets are intercepted to be sent over a virtual private network. When this is done, the link layer data is considered the application data and proceeds back down the IP stack for actual transmission. On the receiving end, the data goes up the IP stack twice, once for routing and the second time for the VPN (Virtual Private Network).

What is Network Layer?

It gets the packets across networks. It transfers data from a source network to destination network. This generally involves routing the packet across a network of networks. In Internet protocol suite, IP (Internet Protocol) performs the basic task of getting packets from source to destination. IP can carry data for a number of different upper layer protocols. These protocols are each identified by a unique protocol number. ICMP and IGMP are protocols 1 and 2 respectively. ICMP (Internet Control Message Protocol) is used to transmit diagnostic information about IP. IGMP (Internet Group Message Protocol) is used to manage IP multicast data. These protocols perform internetwork layer functions. All routing protocols like OSPF and RIP are also part of network layer.

What is Transport Layer?

Transport Layers responsibilities include end to end message transfer capabilities independent of the underlying network along with error control, fragmentation and flow control. End to end message transmission or connecting applications at the transport layer can be categorized as either.
1. Connection oriented (Ex: TCP)
2. Connection less (Ex: UDP)
The transport layer can be thought of literally as a transport mechanism whose responsibility is to make sure that its contents reach its destination safely and soundly unless a higher or lower layer is responsible for safe delivery. The transport layer provides this service of connecting applications together through use of ports.
TCP is connection oriented protocol that addresses numerous reliability issues to provide a reliable byte stream. TCP features are:
1. Data arrives in order
2. Data has minimal error
3. Duplicate data is discarded
4. Lost packets are resent
5. Includes traffic congestion control.
The new transport layer protocol SCTP is a reliable connection oriented, message-stream oriented transport mechanism. It provides multiple streams multiplexed over a single connection. It also provides multi-homing support, in which a connection end can be represented by multiple IP addresses. Such that if one fails, the connection is not interrupted.
UDP is a connection-less data-gram protocol. It is a best effort protocol. Reliability is addressed through error detection using a weak checksum algorithm. It is used for applications such as streaming media (audio, video, VOIP etc.) In these applications timely arrival of data is more important than reliability.
The appropriate transport protocol (TCP, UDP, and SCTP) is chosen based on the higher layer protocol application. For example FTP (file transfer protocol) expects a reliable transfer whereas Network File System assumes non reliable data transfer. Applications like VOIP can tolerate some loss of packets but not reordering or delay that could be caused by re-transmission.

What is Application Layer?

The Application Layer is used by most programs for network communication. Data is passed from the program in an application specific format, then encapsulated into a transport layer protocol. Internet Protocol stack has no layers between application and transport layers. The application layer must include any protocols that act like OSI reference models presentation and session layer protocols. This is done through libraries. Data sent over the network is passed into the application layer where it is encapsulated using the application layer protocol. From there the data is passed down to the lower layer protocol of the transport layer. Two most common end-to-end protocols are TCP and UDP. Common servers have specific ports assigned to them (HTTP has port 80 and Telnet has port 23 etc.) While clients use ephemeral ports. Some protocols such as file transfer protocol (FTP) and Telnet may set up a session using a well known port but then redirect the actual user session to ephemeral ports. Routers and switches do not utilize generally this layer, but some protocols like resource reservation protocol do use application layer.

What is the structure of a typical UNIX file system?

UNIX file system structure is shaped like an upside down tree. Directories enables us to keep related files in one place, where we see them only when we want. Directories can be subdivided into sub-directories and so on. All these comes under a root directory called root. Under the root there are standard directories called administrative directories. Some of the standard administrative directories are bin, dev etc, lib etc.

How does a Floppy Disk work?

A Floppy Disk is a plastic disk coated with magnetic material. Data is stored in the disc in concentric circles called tracks. Each track consists of tiny magnetic spots whose orientation desides whether a ‘1’ or a ‘0’ is stored in that spot. This disc is enclosed in a hard rectangular jacket. There is flat circular metallic connector at center of the disc and a window on the hard jacket-through which the floppy disk can be viewed. This window is usually covered by a metallic covering that is sliding type and fixed on the hard jacket. When floppy is inserted in the floppy disk drive, a spindle goes into the circular connector and make the floppy rotate. The metallic covering over the window is slided and head is positioned over the disc through this window and read/write operations are performed. Commonly available floppy disks are of high density type and they can store upto 1.44 MB data.

What is a file? What are the features of file management?

File is an organised collection of related records. File management is one of the tasks of the operating system. File management is concerned with the logical organisation of information, its security and manipulation. Information is grouped as files and files are grouped under various directories. Files are the leaf nodes of a hierarchial tree structure. Directories are subdivided into sub-directories. File management also includes security features like access rights (read, write, execute and a combination of them). File management also include the physical organisation of files and managing the file structures. File structure can be sequential, indexed, index-sequential etc.
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