Hard Drives

HDD's or Hard Drives usually refers to Hard Disk Drives. Hard disk drives play important role in a computer by storing all the informations of a user such as programs,documents,music etc.   A computer system must have at least one Hard Drive or may  have multiple drives. Hard drives have two positions in a computer system. A hard drive may be positioned  internaly that is inside the computer or may be positioned  externally that is  outside the computer. In a computer system, a hard drive is the slowest part from all the parts of system. The size of a hard drive is measured in Gigabytes (GB).
Types of Hard Drives
Many types of hard disk drives are available today but the main types are few which are differentiate from each other according to their technological structure.

  1)_ SCSI - These hard drives are the fastest hard drives uptill now. They are basically used in servers. SCSI are used in places where only the  best reliability is needed. SCSI drives are highly expensive. Their speeds reach up to 320 MB/s.

  2)_  SATA - SATA is a new era technology. SATA drives are becoming the standard for desktop computers. Their speeds reaches up to 375 MB/s. Because, SATA technology is latest therefore it can not work on older computers. A convertor card is used to use SATA technology in older computers. A  SATA  drive can be used either as internal and external drives depending upon the  requirements of computer system. A computer may use internal SATA drive or may use external SATA drive.

  3)_  IDE or PATA - This technology is in use for many years. Most  systems of the last 15 years suppors this technology. PATA and IDE both refers to the same technology. Infact this technology is the replacement of the SATA. IDE hard drives reaches up to speeds of 133MB/s.

 4)_   USB/ Fire wire - These technologies are used as external hard drives. USB2 is commonly used connection for an external hard drive. External hard drives generally slower than the internal hard drives. The max speed of Fire wire hard  drives reaches up to 60MB/s.

 Spin Speed 
        Besides the type of hard drives, the spin speed of hard drive also matters. The spin speed may vary from as slow as 4800 rpm  to 15000 rpm. RPM is the ‘rotation per minute’. Usually the speed is measure in rpm. Slow spin speed as 4800 rpm is used in laptops and  high spin speed as 15000 rpm is used in SCSI drives. The average spin speed of hard drive  is 7200 rpm..

Cache Size
           Cache size is also an important factor  in hard drives. Usually, the hard drives have a cache of between 8MB to 16MB. The cache is a place where the data is temporarily stored before it is written to the hard disk. The cache is much faster than the drive itself.

      Internal and external hard drives are manufactured by many manufacturers. The popular manufactures for hard drives are Maxtor, Western Digital, Seagate, IBM, FreeCom and LaCie.

CCNA

CCNA  Complete Guide

           This book and its support materials have everything that instructors and students need for an informative,interesting,challenging and entertaining CCNA educational experience. This book includes all the lab setups built using the Dynamips, the Cisco router emulation software. This book contains all the theory and practicle knowledge that an accomplished CCNA must obtain to ace both the CCNA exam and the challenging real life working environments.

Edition : 2nd
Author : Yap Chin Hoong
Download Here : Download

Thinking in C++

Thinking in C++

  

This book in C++  present material in one simple step at a time, so the reader can digest each concept before moving on. Gives simple and short examples that are easy to understand. This book gives the reader a greater sense of accomplishment. This book is also recommended in Virtual University by highly qualified professors.

Edition : 2nd
Author : Bruce Eckel (The Creator of C++)
Download Here :  Download

Physics by Walker

Fundamental of Physics
        This book deals with the basics of physical sciences and gives detailed study of fundamental laws which are applicable on real world. Covers each topic with complete detail and sohpisticated proofs. This book also helps students by giving solved examples which are easy to understand the topics. This book helps a lot to students and professors of physics.
Author : Halliday-Resnick-Walker
Download Here : Download

Discreate Math

Discreate Mathematics & its Applications
               This book helps to cover the major goals of discreate mathematics which include mathematical reasoning,combinatorial analysis,discreate structures,algorithm thinking and applications and modeling. This book helps students in how to think logically and mathematically.
Edition : 7th
Author : Kenneth  H. Rosen
Download Here :  Download

OOP by Robert

OOP in C++ by Robert Lafore

    Object Oriented Programming is a new concept in programming and this book starts by taking concepts of c++ and teach the methods of Object Orientation. Even if anyone has no previous experience in programming then he can read this book and can build concepts with that book. This book is easy, reliable and effective specially for students and professional programmers.
Author : Robert Lafore
Edition : 4th
Download Here : Download

Malware

   A Malware is a type of a virus that works on a computer having internet usage. If a computer is connected to the internet then there might be a chance of malware working on that computer.A malware is a special  type of virus that is causing great damage to the users of internet’s users.
Malware
  Malware is classify as a malicious type of software. A malicious software is one that is installed on a computer without the permission of the user. A malware get access to the user’s informations and performs unwanted actions to software or hardware of the user’s computer.  A malware may also harm the computer or hijack the operating system of user’s computer. A malware may  hijack the browser, serve up unwanted ads, may track online or offline activity and may also unleak the informations of user’s computer. Basically a malware is prepared by a programmer and sometimes a malware is poorly programmed so that it cause the user’s computer to unstable and slow down. There are many reasons due to which a malware is programmed and there is a special purpose of a programmer behind the software. Malware includes many tools with it such as Spyware, Trojans, Adware, rootkits, dialers, Keyloggers, Crimeware, Badware, worms and any other types of unwanted or potentially unwanted software.
Cause of infection
  Malware enters in the computer by different ways. Mostly it enters by downloading freeware and shareware from websites. Such as free toolbars, screen savers and other applications. Malware may also deliver via spam to the targeted computer . The target  computer get  infected when a spam message or infected file is opened. As the result of opening the infected message or file, the malware launches itself in the computer and starts its work that is assigned by the programmer. Malware is also installed from the advertisements that are convincing for the software download for system protection.

Network

A Network is a communication between two or more devices. A computer network is a communication between two or more computers .This communication is build up through communication medium. A communication medium can  be  radio waves, wires, infrared, optical fibers etc.Computer networks have added a new dimension to the 21st century. Today the cyber world is much faster and wider than the real world. This all has been made possible due to computer networks. Computer networks have revolutionized the technology,business and many other matters.Computer network plays important role in our daily lives because of the very important reality that is of communication.  Computer networking is basically used to share resources like  printers, modems, files,fax machines,cameras etc between different users. Besides this, computer networks  are used for database server, computer server, email, chat, internet etc. The computer to which the resources are attached is called the server and the other computers that can access these  resource are called clients.  The sharing of fax machines, printers, and modems among many computers and users  has reduce the operational cost. So, there is no need of separate devices for each user.  A database on a computer network is a very important application as it stores and runs many important data and informations. Computer networks can supports instantaneous communications that include Email and chat among users. Computer networks also facilitate the users to send  files on a computer network.

Generally the computer networks are classified  according to the size of network or area covered by a network. Such as Local Area Networks (LAN), Wide Area Networks (WAN), Metropolitan Area Networks (MAN) and Personal Area Networks (PAN). These networks work in different topology states. The topology  is the way in which the computer networks and network resources are connected with each other. These topologies of the network can be classified as Bus Network, Ring Network and Star Network.The hardware of computer networks mainly  consists of wiring, network cards  and a hub. Purpose of Computer network cards is to maintain  understanding between computers so that one computer can  understand the talk of other computer. Each computer on the network is identified through unique address of network card. Hubs connect all the computers in the network. Hubs can also be used to connect to other hubs to increase the size of the computer network. Wires are also used to connect all computers in the network.
The number of cables increases as the number of computers in an office or a home increases. This creates complexity in wiring. This problem is solved by  wireless networking .  Wireless networking works on radio waves. In wireless networking trans-receivers or infrared signals are used to communicate between computers and devices. Examples of wireless networking include Bluetooth and Wi-Fi.  Although the wireless technology has greater benefits than wire technology but there are certain security issues involved with wireless networking. However, the demand of wireless networking is increasing among the users rapidly.

Security Alarm system

Security alarm system is widely used in most appliances and in many places. Although security alarm is a great ease for us but to understand working of whole security alarm is actually very difficult. To understand the processing of security alarm consider the concept of three main categories under which almost all security alarm components fall: controls, sensors, and output devices.
Controls:
Controls contain the components that control the working of security alarm such as control panel and key-pad.
Control Panel is the hub of the security alarm system. All security alarms sensors are connected to the control panel. It receives signals from sensors and interprets the signals and orders the output devices to take appropriate actions. The output devices in turn sounds the alrm.
Key Pad is another control component which allows user to interact with the security alarm. Through keypad the security alarm can turn on and off. The security alarm is notified by keypad about any additional upgrades by the user.
Sensors:
In security alarm system, a sensor is mainly used for detection purposes. Many types of sensors are used according to the requirement in security alarm system.
Contacts  is a type of sensor which detects  the opening and closing of doors or windows. Contacts  alert the  control panel  when the magnetic bond between the door frame and the door is broken.
Glass Break Detectors  is another sensor that detect sound frequency. Its mainly purpose is the detection of breaking of windows or glass doors. A glass break detector  alerts the alarm system if glass is broken within approximately 35 feet of the detector. Some glass break detectors can have more range.
Motion Detectors  detects  the movements within a pre-set range of a given environment. Motion detectors are one of the most important and widely used security alarm sensors. According to their importance they are further classified into five kinds.
Infrared Motion Detectors : They use infrared or passive infrared (PIR) sensors to alert the security alarm system to the changes in the levels of heat or movement in a location.
Corner Mounted Motion Detectors  :  They are most commonly used motion detector and mostly used in the markets or halls. They are included in many types of security alarm systems. They are mostly placed in the corner of a room to offer a wide range of motion detection.
Ceiling Mounted Motion Detectors  : They are more powerful than corner mounted because they  alert  security alarm to virtually all movements  and   give full-360º coverage. They are used in places where corner mounted detectors would be blocked by doors, shelves, or other stationary objects.
Pet Immune Motion Detectors : They are temperature detectors. They uses PIR(passive infrared) technology and  alerts the alarm system when large changes in temperature are detected, not the smaller changes.
Outdoor Motion Detectors : They cause the alarm system to turn on lights if a person or vehicle is within a certain range of the motion detector.
Output Devices:
Out devices serves the output in security alarm and many types of outputs are used according to the requirement in security alarm system.For example: Sirens, Lights.
Siren is the output device  and it produces  a loud sound when it is call by  the control panel of alarm system. Siren is used in silence places where there is a dangour of  anyone or it is used on other places also. Strobe Lights are also the output device and when alarm system detects  an unwanted activity the strobe lights are called by the control panel and strobe lights repeatedly turn on and off.

GPS system and devices

GPS fleet tracking devices are becoming more popular now a days. GPS stands for Global Positioning System. GPS devices are mostly used in cars. GPS uses a special system that can send messages to a computerized tracking system. These systems are build up of three parts. One part is the actual product which is placed in a car to gather informations to send to the next part. The actual product in a car monitors the car’s speed and location of a car on the map. The computerized marker on the map will expose the real location. Part two of this system is the receiver that also stores the data. The third part of the GPS system is the user interface, also referred to as the U.I. The U.I allows a user to interact with GPS device and access the data.GPS fleet tracking systems are becoming more common in business and in personal usage. Many businesses have workers who use company vehicles to perform their jobs. These include postal workers,  truck drivers, operators of delivery vans, school buses, metro transportation, dump trucks, ambulances and many others. And the companies wants to keep track their workers and vehicles for smooth running of their business. Now, the companies use GPS devices to make sure that cars are being driven safely and that their employees are safe on the road. An unsafe motorist could be a huge liability to the company if he or she has risky driving habits. And also by use of it the Insurance companies give cut rates when vehicles are being monitored for safety. And by GPS system the company track on car if it is used for personal purpose that’s the great benefit for the company. By use of GPS devices the family members can keep track of their other family members which promotes safety. By Monitoring the driving habits of children the parents know about their children. If a car is lost then it can be regained by GPS system and thieves can be caught by police. If a worker or a driver tells a lie about his position then his boss can track his position by GPS system. In other words, the GPS devices have many advantages and they give more easiness and reliability to its users.