What are the different type of networking

What are the different type of networking / internetworking devices?

Answer:

Repeater:
Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.

Bridges:

These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and
thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.

Routers:

They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of
the several possible paths is the best for a particular transmission.

Gateways:

They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol
before forwarding it. They operate in all seven layers of the OSI model.

Describe the CMOS

Describe the CMOS?

Answer:

CMOS (Complimentary Metal Oxide Semiconductor) is a small amount of memory in a special RAM chip. Its memory is maintained with electric power from a small battery. Certain system data are stored in this chip. They must be read to make the PC operable. There may be 100 to 200 bytes of data regarding date, time, floppy and hard disk drives, and much more.
CMOS data can be divided in two groups:
* Data, which POST can not find during the system test.
* Data, which contain user options.
For example, POST cannot by itself find sufficient information about the floppy drive(s). Floppy drives are so "dumb," that POST cannot read whether they are floppy drives or not, nor what type. About the same goes for IDE hard disks, while EIDE hard disks are a little more "intelligent," However, POST still needs assistance to identify them 100% correctly.
The same goes for RAM: POST can count how much RAM is in the PC. However, POST cannot detect whether it is FPM, EDO or SD RAM. Since the CPU and BIOS reads data from RAM chips differently, depending on the RAM type, that type must be identified.

Configuration

The PC must be configured, be supplied with this information. That is done in the factory or store, where it is assembled. This information is stored in CMOS, where they stay. CMOS data only need to be updated, when different or additional hardware components are installed. This could be a different type hard disk or floppy disks or an new RAM type, Often he user can do this.
Other data in CMOS contain various user options. Those are data, which you can write to CMOS. For example, you can adjust date and time, which the PC then adjusts every second. You can also choose between different system parameters.
Maybe you want a short system check instead of a long one. Or if you want the PC to try to boot from hard disk C before trying floppy disk A, or vice versa. These options can be written to CMOS.
Many of the options are of no interest to the ordinary user. These are options, which regard controller chips on the system board, which can be configured in different ways. Ordinarily, there is no need to make such changes. The system board manufacturer has already selected the optimal configurations. They recommend in their manuals, that you do not change these default settings.
We can conclude, that CMOS data are essential system data, which are vital for operation of the PC. Their special feature is,

Describe the ASCII

Describe the ASCII?

Answer:

ASCII means American Standard Code for Information Interchange. It is an industry standard, which assigns letters, numbers, and other characters within the 256 slots available in the 8 bit code.
The ASCII table is divided in 3 sections:
*Non printable system codes between 0 and 31.
*"Lower ASCII" between 32 and 127. This part of the table originates from older, American ADP systems, which work d on 7 bit character tables. Foreign letters, like Ø and Ü were not available then.

*"Higher ASCII" between 128 and 255. This part is programmable, in that you can exchange characters, based on which language you want to write in. Foreign letters are placed in this part.

An example
Let us imagine a stream of bits sent from the keyboard to the computer. When you type, streams of 8 bits are sent to the computer. Let us look at a series of bits:
001100010011001000110011
Bits are combined into bytes (each 8 bits). These 24 bits are interpreted as three bytes. Let us read them as bytes:
00110001,
00110010, and 00110011.
When we convert these byte binary numbers to decimal numbers, you will see that they read as 49, 50, and 51 in decimal numbers. To interpret these numbers, we have to look at the ASCII table. You will find that you have typed the numbers 1, 2, and 3.

Describe the LCD screens

Describe the LCD screens?

Answer:

The big, heavy traditional monitors will eventually be phased out. They will be replaced by the thin and "soft"
LCD (Liquid Crystal Display) screens! It may be a few years before this technology will be dominating, but it
is bound to happen. The LCD screens are excellent, and actually they are already available.
The LCD screen is flat, since it contains no cathode ray tube (CRT). In stead the screen image is generated
on a flat plastic disk. Here you see a Siemens Nixdorf 3501T. It produces a sharp high resolution image -
better than any others I have seen.

LCD screens are also called "soft" screens, since their images have a softer quality than those from
traditional CRT monitors. The image does not flicker thus causing less eye strain. People who have become
accustomed to these soft images will not return to the traditional monitors. At the same time the LCD screen
is by far the most environmentally safe product. These flat screens emit zero radiation, and they consume
significantly less power than the traditional monitors. Another reason to expect LCD screens to become the
monitors of the future.

What is an operating system

What is an operating system?

Answer:

The operating system can be evaluated from different angles:
An operating system is a number of files, which are read from the hard disk at the end of of the PC
start-up routine.

An operating system is a program layer. It connects to the the PC hardware, to facilitate optimal
execution of the user programs.

The first definition does not say much. Let us start with the second: The operating systems links software
and hardware together. It has to enable user programs, like Works, Office, etc., to function with all
possible hardware configurations. You can imagine the relationship between hardware and user
programs thus:
Hardware is clumsy and dissimilar. There are untold variations of PC's. They can have one or
another type hard disk, CPU, video card, etc. All of these various PC configurations behave each in
their own way.

The use programs are 100% similar. They are off the shelf products, which expect the PC to
respond in a certain manner.

How do we make these two layers work together? Can we eliminate out the differences in the PC
hardware, so a standard product like Works just functions? Yes we can. We read in an operating system
- a system layer, which smoothes out and standardizes the hardware:

You should understand the operating system as a necessary layer, which smoothes out bumps and pot
holes in your PC's hardware. This will give the user programs a stable, even work platform.

What are file systems

What are file systems?

Answer:

As I wrote in module 4a, drives are storage media, which can hold a file system. When a disk is formatted in a
drive, it becomes organized and prepared to receive data. When we format a disk, it receives a file system.
Formatting can be compared to starting a library. You must install the book shelves and the catalogue system before any books are put in place. Once the library is ready, bring on the books! Similarly with a disk. When we format it, we "burn in" a file system to make it ready to receive data (files).
We can format with any one of several different file systems:
*FAT (File Allocation Table), the original, old 16 bit DOS system is probably used in 90% of all PC’s. It is
also called FAT16 contrary to:

*FAT32 a new addition to FAT, which Microsoft introduced with Windows 95 B – The December -96 version
(OSR2).

*HPFS (High Performance File System) from OS/2. It is an advanced 32 bit file system, which in all
respects is far superior to FAT, except for possible usage. It can only be used with OS/2.

*NTFS from Windows NT. A 32 bit file system like HPFS, but not compatible with it. NTFS can,
unfortunately, only be used in Windows NT. If it was available for use in Windows 95, it would be far to
preferable to FAT and FAT32.

*NetWare is a server operating system from Novell. It has its own 32 bit file system. For that reason, the
Novell server, contrary to NT or OS/2 servers, cannot be used as a work station. The file system is much
faster than FAT, but it works only with Novell servers (typically file servers).

* UNIX servers have their own filing system. Here the use of upper/lower case in file naming is significant.
Read in the following pages about the concepts of these file systems.

What do you gain with SCSI

What do you gain with SCSI?

Answer:

Expensive but good: SCSI makes the PC a little more expensive, but much better. That's all. The
advantages are, that on the same PC you have free access to use many units and good hard disks:
*It is easy to add many high end accessories, such as DAT-streamers, CD-ROM recorders,
MO drives, scanners, etc.

*You can use SCSI hard disks.
*You can use CD-ROM drives on SCSI , where they perform a lot better than on IDE.

Advantages of SCSI hard disks

SCSI hard disk are generally of higher quality than other disks. EIDE disks come in various qualities from
different manufacturers. However, even the best EIDE disks cannot compete with the best SCSI disks.
Typically, good SCSI disks come with a 5 year warranty. They come in larger capacities than the EIDE
disks and they are faster. At 5400, 7200 or 10.000 RPM they have shorter seek times. They also have a
bigger cache.
Another advantage is the large number of accessories, which can be attached. If you buy a 4 GB SCSI
disk today, you will guaranteed need additional disk storage in a few years. Then you just add disk
number two to the SCSI chain, and later number three. The system is more flexible than EIDE, where
you can have a maximum of four units incl. CD-ROM.
The SCSI hard disks can also adjust the sequence in the PC's disk read commands. This allows to read
the tracks in an optimal sequence, enabling minimal movements of the read/write head. Quantum calls
this technology ORCA (Optimized Reordering Command Algorithm). It should improve performance by
20%.
Finally, the SCSI controller can multitask, so the CPU is not locked up during hard disk operations, which
you can experience with IDE.
SCSI hard disks can achieve substantially larger transfer capacity than the IDE drives, but they have the
same bottle necks: the serial handling of bits in the read/write head, where the capacity is highly
dependent on the rotation speed.