· What is a computer?
The term computer is used to describe a device made up of electronic and electro mechanical components. The computer itself cannot perform any task and is referred to as hardware.A computer system consists of three elements.
1. Hardware 2. Software 3. People
1.Hardware : The physical components which you can see, touch and feel in the computer system are called hardware Eg monitor, keyboard, mouse etc.
2.Software : Software is used to describe the instructions that tells the computer how to perform a task. Software is categorized
1) System Software’s ( e.g. . Operating Systems, Compilers, Editors etc)
2) Application Software’s (e.g. MS-Word, Excel, Accounting packages etc)
3.People : People who operate the computer and also create computer software Instructions and related program like front hand and back hand site.
· Computer System types
We can classify systems into the following categories :
- 8-bit, for Ex: 8085 microprocessor
- 16-bit, for Ex : 8086, 286, 386 processor
- 32-bit , for Ex : 486
- 64-bit, for Ex: Pentium – II, Pentium – III, Pentium – VI, Pentium – D and Core to Due,and Dule Core System Are available
- This gives us Two basic System Types or Classes of Hardware.
- 8-bit ( PC/XT) class systems
- 16/32/64 (AT) class systems
PC stands for personal computers, XT stands for eXTended PC, and AT stands for an advance technology PC.The XT basically was a PC system that included a hard disk for storage.And also floppy drive found in the basic PC system. These systems has an8-bit processor and an 8-bit INDUSTRY STANDARD ARCHITECTURE (ISA) bus for system expansion. Bus is the name given to expansion slots in which additional plug in circuit board can be installed.16-bit and greater systems are said to be AT class. 16-bit (and latter 32 and 64 bit) processors and expansion slots are included. The first AT class systems had a 16-bit version of the ISA bus which is an extension of the original 8-bit ISA bus found in the PC/XT class systems. Afterwards several expansion slots were developed for AT class systems.
For Example
- 16/32 bit PS/2 microchannel architecture (MCA) bus.
- 16-bit PC card (PCMCIA) bus
- 16 bit ISA bus
- 16/32 bit Extended ISA(EISA) bus
- 32/64 - bit card Peripheral Component Interconnect (PCI) bus.
Easy way to identify a PC/XT system is by the 8-bit ISA expansion slotsregardless of the processor present in the system. AT systems can be similarlyidentified by having 16-bit of greater slots of any type (ISA, EISA, PCI) slots.
· Computer hardware
Basic components in a computer system are central processing unit (CPU),memory, one is input device and second is output device.
- List of System components
1. Motherboard
2. Processor
3. Memory (RAM)
4. Hard disk
5. CD-ROM
6. Floppy Drive
7. Keyboard
8. Mouse
9. Monitor
10. Power Supply
11. Cabinet
The figure definition of Motherboard
· Describe all components of motherboard.
Processor
The processor is often thought as the engine of the computer. Then the processor reads the commands from the memory and then executes them. the processor is one of the most expensive parts of the computers and is also one of the smallest parts.
Primary Memory
Memory : Is used to hold programs and data during execution.
Primary memory is often called as RAM(Random Access Memory). It holds all the programs and data the processor is using at a given time. RAM is volatile because its contents are erased when power is switched off. The other type of system memory is ROM(Read only Memory)which is permanent because it contents are not erased even when power is switched off. It is usually used to load an operating system.
Hard disk drive
A hard drive consists of spinning platters made up of aluminum or ceramic that is coated with magnetic media. The platters come in various sizes. The hard drive with many different storage capacities can be created depending upon the density, size and number of platters.This is also called as Secondary memory. There can be several programs in the system, which cannot be stored in RAM, so we need a very huge non-volatilememory, which can be used for storing all the programs, and data when the system is not in use are called as Hard disks.
CD-ROM drive
CD-ROM stands for compact disk read only memory. It consists of small diskssimilar to the gramophone records to hold digital information. As the name applies they are read only medium. With the advancement in technology writable CD’s are also available.
Floppy Disk Drive
Floppy disks are the slowest and the smallest form of secondary storage. They provide a simple way to carry information from one place to another, and backup small amount of files. In modern days floppy drive component is not as important as it was years ago. All PC’s made in the last 10 years use a standard 3 ½ inch, 1.44 MB capacity floppy drive.
Keyboard
The keyboard is the main input device for most computers. It is used to input text or enter commands into the PC. Nowadays keyboards with additional features are available like multimedia keyboard, wireless keyboard.
Mouse
With the invention of graphical user interface mouse is used to input information into the computer. Users simply point and click to enter information. The main advantage of mouse over keyboard is simplicity. And there are many operations that are much easier to perform with a mouse then a keyboard.
Monitor
The monitor is the specialized high-resolution screen similar to a television. The video card sends the data of its video memory to the monitor at a rate of 60 or more time per second. The actual display screen is made up or red, green and blue dots that are illuminated by electron beam from behind. The video card DAC chip controls the movement of the electron beam, which then controls what dots are turned on and how bright they are. Which then determines the picture you see on the screen.
Power supply
SMPS(Switch Mode Power Supply):
The power supply supplies power to every single part in the PC. The main function of the power supply is to convert the 230 V AC into 3.3 V, 5 V and 12 V DC power that the system requires for the operations. In addition to supplying power to run the system, the power supply also ensures that the system does not run unless the power supplied is sufficient to operate the system properly. The power supply completes internal checks and tests before allowing the system to start. If the tests are successful, the power supply sends a special signal to the motherboard called Power_Good. If this signal is not present continuously, the computer does not run. Therefore, when the AC voltage dips and the power supply becomes stressed or overheated, the Power_Good signal goes down and forces a system reset or complete shutdown.
Cabinet
The box or outer shell that houses most of the computers. The cabinet actually performs several important functions for your PC including protection to the system components, directing cooling airflow, and allowing installation of and access to the system components. The cabinet often includes a matching power supply and must also be designed with shape of the motherboard and other system components in mind.
Peripheral Devices
Any external device, which is not necessary to perform the basic operation of computer, is called as peripherals List Of All Device is:
Printers, Modems, Speakers etc.
Modem
Modem (Modulator and Demodulator) is typically used to send digital data over a phone line. The sending modem converts digital data into analog data,which can be transmitted over telephone lines, and the receiving modem converts the analog data back into digital form. This is used to connect to
Internet.
Modems are available in different capacities.
- 300 bps - 1960s through 1983 or so
- 1200 bps - Gained popularity in 1984 and 1985
- 2400 bps
- 9600 bps - First appeared in late 1990 and early 1991
- 19.2 kilobits per second (Kbps)
- 28.8 Kbps
- 33.6 Kbps
- 56 Kbps - Became the standard in 1998
- 10 Computer Hardware
- ADSL, with theoretical maximum of up to 8 megabits per second (Mbps)
Printers
The capability to produce a printed version often called a hard copy of a document is the primary function of a printer.Different types of printers are (1) Laser (2) Inkjet (3) Dot-Matrix.
· Motherboard Form Factors
Early PCs used the AT form factor and 12in wide motherboards. The size of an AT motherboard caused problems for upgrading PCs and did not allow use of the increasingly popular slimline desktop cases. These problems were largely addressed by the smaller version of the full AT form factor, the Baby AT, introduced in 1989. Whilst this remains a common form factor, there have been several improvements since. There are several common form factors used for PC motherboards. The form factors refer to the physical dimensions and size of the board, and dictates what type case is motherboard will fit into. The PC motherboard form factors generally available include the following.
- Baby – AT NLX
- LPX Backplane systems
- ATX Proprietary designs
BAT(Baby –AT)
The Baby AT (BAT) format reduced the dimensions of the motherboard to a
typical 9in wide by 10in long, and BAT motherboards are generally important by their shape, an AT-style keyboard connector soldered to the board and serial and parallel port connectors which are attached using cables between the physical ports mounted on the system case and corresponding connectors located on the motherboard.
With the BAT design the processor socket is located at the front of the motherboard, and fulllength expansion cards are intended to extend over it. This means that removing the processor requires the removal of some or all expansion cards first. Problems were exacerbated by the increasing speeds of Pentium-class processors.
System cooling relied on the AT power supply blowing air out of the chassis enclosure and, due to the distance between the power supply and the CPU, an additional chassis fan or active heatsink became a necessity to maintain good airflow across the CPU. AT power supplies only provide 12V and 5V outputs to the motherboard, requiring additional regulators on the motherboard if 3.3V
ATX
The Intel Advanced/ML motherboard, launched in 1996, was designed to solve these issues and marked the beginning of a new era in motherboard design. Its size and layout are completely different to the BAT format, following a new scheme known as ATX. The dimensions of a standard ATX board are 12in wide by 9.6in long; the mini ATX variant is typically of the order 11.2in by 8.2in. The ATX design gets round the problem by moving the CPU socket and the voltage regulator to the right-hand side of the expansion bus. Room is made for the CPU by making the card slightly wider, and shrinking or integrating components such as the Flash BIOS, I/O logic and keyboard controller. This means the board need only be half as deep as a full size Baby AT, and figure of ATX Motherboard there’s no obstruction whatsoever to the six expansion slots (two ISA, one ISA/PCI, three PCI).
The ATX uses a new specification of power supply that can be powered on or off by a signal from the motherboard. This allows notebook-style power management and software-controlled shutdown and power-up. A 3.3V output is also provided directly from the power supply.
Mini-ATX is simply a smaller version of a full-sized ATX board. On both designs,parallel, serial, PS/2 keyboard and mouse ports are located on a double-height I/O shield at the rear. Being soldered directly onto the board generally means no need for cable interconnects to the on-board I/O ports.
NLX
Intel’s NLX design, introduced in 1997, is an improvement on the LPX design for low-profile systems, with an emphasis on ease of maintenance. The NLX format is smaller, typically 8.8in wide by 13in long, so well suited for low-profile desktop cases. All expansion slots, power cables and peripheral connectors are located on an edge-mounted riser card, allowing simple removal of the main motherboard, which is mounted on rails in the chassis. It uses a fullwidth I/O shield to allow for different combinations of rear-panel I/O. The design allows for use of an
AGP card, but the slot must be on the motherboard, which reduces the ease of maintenance when such a card is implemented. AGP card, but the slot must be on the motherboard, which reduces the ease of maintenance when such a card is implemented.
Proprietary designs motherboards that are not one of the standard form factors such as Fullsized –AT, Baby- AT, ATX or NLX are called as proprietary.
Backplane systems: One type of proprietary design is the backplane system. These systems donot have a motherboard, the components normally found on the motherboard are located on an expansion adapter card plugged into a slot. In these systems, the board with the slots is called a backplane rather than a motherboard. Systems using this type of constructions are called backplane systems.
Motherboard components
· Expansion slots
· CPU(Main Processor)
· Coprocessor
· Memory
· BIOS and
· Support circuits of chipset for interrupt, DMA etc.
Expansion Slots
The expansion slots are long thin connectors on the motherboard, near the backside of the computer. Various expansion cards are connected to the motherboards through data, address and control lines/buses on these slots. One can connect various expansion cards such as display card, hard drive controller, sound card, network card, modem card etc. on these slots. When an adapter card is connected to the expansion slot, it is actually connected to the data, address and control bus on the motherboard.
Bus : A bus is an electronic path on which signals are sent from one part of the computer to another.These buses are categorizes according to the number of BINARY DIGITS (bits) that can transfer at a time
- If the data bus is 8 bit wide then it can transfer 8 bits of information at a time and called an 8 bit bus.
- On a 8 bit data bus transferring 16 bit data requires two data transfers 20 Computer Hardware
Another very common term while talking about bus is , its “ bandwidth”. The bandwidth of a bus is the measure of data that can fit in the bus at a given time.
You can increase the data movement through a bus either by increasing the bus width( from 8 bit to 16 bit) of by increasing the bus bandwidth (8 Mhz to 20 Mhz). This is similar to the way you can increase water output from a pipe, either you can increase the pipe diameter or you can increase the water flow. Data Bus : Is a set of wires or tracks on the motherboard. Data bus is used to transfer data from one part of the computer to another part. Address Bus : is a set of wires or tracks on the motherboard Printed Circuit Board(PCB) which is used to specify address of a memory location Depending on the width and the technology, the expansion slot bus can be divided into the following categories.
- 8 bit ISA
- 16 bit ISA
- MCA
- EISA
- VESA local bus or VL bus
- PCI local Bus
-
CPU (Main Processor)
The main component of any motherboard is the main processor chip which controls all the inner functions of the system. The CENTRAL PROCESSING UNIT(CPU) functions as the brain of every PC.
It is usually inserted into the socket and is not soldered onto the motherboard as many other chips are normally done, this makes its replacement, in case ofany problem, very easy. Some of the common CPU chips are inter 8088,8086,80286,80386,80486, Pentium, Pentium MMX, Pentium –II, Pentium III, Pentium – IV etc
Coprocessor
Coprocessor is a special purpose microprocessor, which is used to spped up main processor job by taking over some of the main processors work. Most common type of coprocessor is a math coprocessor. Coprocessor chips are used to help the main processor in carrying out its various functions.
A math coproessor helps main processor in performing mathematical calculations Older system (XT, AT, AT-386) required a coprocessor chips to be inserted into special socket on the motherboard, but the current feneration of CPU’s have math coprocessor built inside the main processor itself.
Memory
Memory is the place where computer stores the program(set of instructions telling ehe computer what to do), and data that help the program in carrying out its operations. For Ex, a marks sheet printing program will require students rollnumber, name and marks obtained in various subjects etc. as data.There is basically two type of memory used in a computer.
- RAM memory
- ROM memory
RAM:
RAM or random access memory is a read/write type of memory which is used by the processor to keep program, data and intermediate results during program executions. It is VOLATILE type of memory, which lose ists content when the power
supply to it is switched off. The physical installation of RAM memory on the motherboard can take place in various ways.
- DIP(dual In-line Pin) memory chips were used on initial motherboards.
- Later SIMM ( single inline memory modules) became common.
- Currently DIMM(dual inline memory modules) are most common
memory module.
- Bit is a binary digit that is either 0 or 1.
- Nibble is collection of 4 bits.
- Byte is collection of 8 bits.
- Kilobyte is 1024 bytes
- Megabyte is 1024 Kilobytes
- Gigabyte is 1024 Megabytes
Read Only Memory(ROM)
ROM or Read Only Memory, as its name suggest is a read only type of memory it cannot be written. Data is written into it by the manufacturer.
- On major advantage with the ROM is, ROM is Non-Volatile type of memory i.e it does not lose its content when the power supply to it is switched off.
- A motherboard normally contains one or more of these ROM chips.
- The memory capacity of a ROM varies from one type of system to another.64 KiloByte (KB) was normally sufficient for a XT system, whereas as AT system requires 256KB of ROM.
BIOS
BIOS is an abbreviation if Basic Input Output System. It is one of the most important program stored in the ROM. BIOS program lets your application program and the hardware such as floppy disk, hard disk, video adapter etc. communicate with each other.
It is pronounced “bye-os”.
- The BIOS also contains a program called Power-On-Self-Test or POST. This post program checks the motherboard and other devices connected to the computer during the system power-on time. IBM made the original BIOS for their copyright product, but many compatible BIOS program BIOS program are available from Award, Phoenix, American Megatrends Inc. (AMI) etc. various manufacturers.
Cache Memory:
A small amount (normally less than 1MB) of high-speed memory residing on or close to the CPU. Cache memory supplies the processor with the most frequently requested data and instructions. Level 1 cache (primary cache) is the cache closest to the processor. Level 2 cache is the cache second closest to the processor and is usually on the motherboard.
Support Chips/Chipsets
Apart from the processor chip and the memory, Motherboard also contains many controller chips and other devices which everything together.
- A typical system required interrupt controller, DMS controller, Timer chip, Clock chip, Bus controller chip, I/O peripheral interface chip etc, to make the computer work as a complete unit.
- The IBM PC, XT, AT, Pentium etc. use standard Inter chips intended for any computer built around an Intel CPU.
- Modern developments in electronics have made it possible to produce VERY LARGE SCALE INTEGRATED CIRCUITS(VLSIC), and now just two or three of these VLSIC chips can do the work which were previously performed by dozens of different chips.
- These set of VLSIC chips are called ‘CHIPSETS’.
- A typical chipset contains in one or two VLSIC chips all the support logic required by the processor to function as a complete system.
- Many of these chipset maker include serial and parallel ports, floppy and hard disk controllers, USB support, LAN and audio support, and display adapter on the chipset itself. Large-scale integration along with high –capacity memory chips has let to even fewer components on a PC’s motherboard.
Motherboard Configuration
A typical motherboard has several options and proper configuration is required to select the required hardware setup.
- Most of the PC and XT class motherboards are set/configured using jumpers or switches on the motherboard.
- In the AT and later machines, the configuration options are stored in CMOS RAM and are set using the SETUP utility in the BIOS ROM. The motherboard configuration should always be perfect, as an incorrectly setup motherboard can cause the system to malfunction or even crash.
Ports
Introduction
The most basic communication ports in any PC system are the serial and parallel ports. The serial ports were originally used for devices that must communicate bi-directional with the system. Such devices include modems, mice, scanners and any other devices that “ talk to” and receive information from the PC Newer parallel port standards now allow the parallel port to perform highspeed bi-directional communications.
Serial ports
Considered to be one of the most basic external connections to a computer, the serial port has been an integral part of most computers for more than 20 years.Although many of the newer systems have done away with the serial port completely in favor of USBconnections, most modems still use the serial port, as do some printers, PDAs and digital cameras. Few computers have more than two serial ports.
Two serial ports on the back of a PC Essentially, serial ports provide a standard connector and protocol to let you attach devices, such as modems, to your computer.
UART Needed
All computer operating systems in use today support serial ports, because serial ports have been around for decades. Parallel ports are a more recent invention and are much faster than serial ports. USB ports are only a few years old, and will likely replace both serial and parallel ports completely over the next several years. The name “serial” comes from the fact that a serial port “serializes” data.
it takes a byte of data and transmits the 8 bits in the byte one at a time. The advantage is that a serial port needs only one wire to transmit the 8 bits (while a parallel port needs 8). The disadvantage is that it takes 8 times longer to transmit the data than it would if there were 8 wires. Serial ports lower cable costs and make cables smaller. Before each byte of data, a serial port sends a start bit, which is a single bit with a value of 0. After each byte of data, it sends a stop bit to signal that the byte is complete. It may also send a parity bit.
Serial ports, also called communication (COM) ports, are bi-directional. Bidirectional communication allows each device to receive data as well as transmit it. Serial devices use different pins to receive and transmit data — using the same pins would limit communication to half-duplex, meaning that information could only travel in one direction at a time. Using different pins allows for full-duplex communication, in which information can travel in both directions at once.
FigOF This 40-pin Dual Inline Package (DIP) chip is a variation of the National
Semiconductor NS16550D UART chip.
Serial ports rely on a special controller chip, the Universal Asynchronous Receiver/Transmitter (UART), to function properly. The UART chip takes the parallel output of the computer’s system bus and transforms it into serial form for transmission through the serial port. In order to function faster, most UART chips have a built-in buffer of anywhere from 16 to 64 kilobytes. This buffer allows the chip to cache data coming in from the system bus while it is processing data going out to the serial port. While most standard serial ports have a maximum transfer rate of 115 Kbps (kilobits per second), high speed serial ports, such as Enhanced Serial Port (ESP) and Super Enhanced Serial Port (Super ESP), can reach data transfer rates of 460 Kbps.
The Serial Connection
The external connector for a serial port can be either 9 pins or 25 pins. Originally, the primary use of a serial port was to connect a modem to your computer. The pin assignments reflect that. Let’s take a closer look at what happens at each pin when a modem is connected.
Fig OF Close-up of 9-pin and 25-pin serial connectors 9-pin connector:
1. Carrier Detect - Determines if the modem is connected to a working phone line.
2. Receive Data - Computer receives information sent from the modem.
3.Transmit Data - Computer sends information to the modem.
4.Data Terminal Ready - Computer tells the modem that it is ready to talk.
5.Signal Ground - Pin is grounded.
6.Data Set Ready - Modem tells the computer that it is ready to talk.
7. Request To Send - Computer asks the modem if it can send information.
8. Clear To Send - Modem tells the computer that it can send information.
9. Ring Indicator - Once a call has been placed, computer acknowledges signal (sent from modem) that a ring is detected.
25-pin connector:
1. Not Used
2. Transmit Data - Computer sends information to the modem.
3. Receive Data - Computer receives information sent from the modem.
4. Request To Send - Computer asks the modem if it can send information.
5. Clear To Send - Modem tells the computer that it can send information.
6. Data Set Ready - Modem tells the computer that it is ready to talk.
7. Signal Ground - Pin is grounded.
8. Received Line Signal Detector -Determines if the modem is connected to a working phone line.
9. Not Used: Transmit Current Loop Return (+)
10. Not Used
11. Not Used: Transmit Current Loop Data (-)
12. Not Used
13. Not Used
14. Not Used
15. Not Used
16. Not Used
17. Not Used
18. Not Used: Receive Current Loop Data (+)
19. Not Used
20. Data Terminal Ready – Computer tells the modem that it is ready to talk.
21. Not Used
22. Ring Indicator - Once a call has been placed, computer acknowledges signal (sent from modem) that a ring is detected.
23. Not Used
24. Not Used
25. Not Used: Receive Current Loop Return (-)
Voltage sent over the pins can be in one of two states, On or Off. On (binary value “1”) means that the pin is transmitting a signal between -3 and -25 volts, while Off (binary value “0”) means that it is transmitting a signal between +3 and +25 volts...
Parallel Ports
If you have a printer connected to your computer, there is a good chance that it uses the parallel port. While USB is becoming increasingly popular, the parallel port is still a commonly used interface for printers.
Fig of A typical parallel port on the back of your computer
Parallel ports can be used to connect a host of popular computer peripherals:
- Printers
- Scanners
- 30 Computer Hardware
- CD burners
- External hard drives
- Iomega Zip removable drives
- Network adapters
- Tape backup drives
Parallel Port Basics
Parallel ports were originally developed by IBM as a way to connect a printer to your PC. When IBM was in the process of designing the PC, the company wanted the computer to work with printers offered by Centronics, a top printer manufacturer at the time. IBM decided not to use the same port interface on the computer that Centronics used on the printer.
Instead, IBM engineers coupled a 25-pin connector, DB-25, with a 36-pin Centronics connector to create a special cable to connect the printer to the computer. Other printer manufacturers ended up adopting the Centronics interface, making this strange hybrid cable an unlikely de facto standard. When a PC sends data to a printer or other device using a parallel port, it sends 8 bits of data (1 byte) at a time. These 8 bits are transmitted parallel to each other, as opposed to the same eight bits being transmitted serially (all in a single row) througha serial port. The standard parallel port is capable of sending 50 to 100 kilobytes of data per second. Table 2.2.1 Comparison of DB-25 and Centronics 36 Parallel ports
SPP/EPP/ECP
The original specification for parallel ports was unidirectional, meaning that data only traveled in one direction for each pin. With the introduction of the PS/2 in 1987, IBM offered a new bidirectional parallel port design. This mode is commonly known as Standard Parallel Port (SPP) and has completely replaced the original design. Bidirectional communication allows each device to receive data as well as transmit it. Many devices use the eight pins
(2 through 9) originally designated for data. Using the same eight pins limits communication to half-duplex, meaning that information can only travel in one direction at a time. But pins 18 through 25, originally just used as grounds, can be used as data pins also. This allows for full-duplex (both directions at the same time) communication. Table of EPP Pins
Enhanced Parallel Port (EPP) was created by Intel, Xircom and Zenith in 1991. EPP allows for much more data, 500 kilobytes to 2 megabytes, to be transferred each second. It was targeted specifically for non-printer devices that would attach to the parallel port, particularly storage devices that needed the highest possible transfer rate.
Close on the heels of the introduction of EPP, Microsoft and Hewlett Packard jointly announced a specification called Extended Capabilities Port (ECP) in 1992. While EPP was geared toward other devices, ECP was designed to provide improved speed and functionality for printers
Table of ECP Pins
In 1994, the IEEE 1284 standard was released. It included the twospecifications for parallel port devices, EPP and ECP. In order for them towork, both the operating system andthe device must support the requiredspecification. This is seldom a problem today sincemost computers supportSPP, ECP and EPP and will detect which mode needs to be used, dependingon the attached device. If you need to manually select a mode, you can do so
through the BIOS on most computers.
What is USB?
Anyone who has been around computers for more than two or three years knows the problem that the Universal Serial Bus is trying to solve — in the past, connecting devices to computers has been a real headache
Fig of USB Connector
- Printers connected to parallel printer ports, and most computers only came with one. Things like Zip drives, which need a high-speed connection into the computer, would use the parallel port as well, often with limited success and not much speed.
- Modems used the serial port, but so did some printers and a variety of odd things like Palm Pilots and digital cameras. Most computers have at most two serial ports, and they are very slow in most cases.
- Devices that needed faster connections came with their own cards, which had to fit in a card slot inside the computer’s case. Unfortunately, the number of card slots is limited and you needed a Ph.D. to install the software for some of the cards.
- The goal of USB is to end all of these headaches. The Universal Serial Bus gives you a single, standardized, easy-to-use way to connect up to 127 devices to a computer.
- Just about every peripheral made now comes in a USB version. A sample list of USB devices that you can buy today includes:
1. Printers
2. Scanners
3. Mice
4. Joysticks
5. Flight yokes
6. Digital cameras
7. Webcams
8. Scientific data acquisition devices
9. Modems
10. Speakers
11. Telephones
12. Video phones
13. Storage devices such as Zip drives
14. Network connections
How USB Ports Work ?
Just about any computer that you buy today comes with one or more Universal Serial Bus connectors on the back. These USB connectors let you attach everything from mice to printers to your computer quickly and easily. The operating system supports USB as well, so the installation of the device drivers is quick and easy, too. Compared to other ways of connecting devices to your computer (including parallel ports, serial ports and special cards that you install inside the computer’s case), USB devices are incredibly simple! Just about any computer that you buy today comes with one or more Universal Serial Bus connectors on the back. These USB connectors let you attach everything from mice to printers to your computer quickly and easily. The operating system supports USB as well, so the installation of the device drivers is quick and easy, too. Compared to other ways of connecting devices to your computer (including parallel ports, serial ports and special cards that you install inside the computer’s case), USB devices are incredibly simple!
· USB Connections
Connecting a USB device to a computer is simple — you find the USB connector on the back of your machine and plug the USB connector into it. Fig of USB Connections If it is a new device, the operating system auto-detects it and asks for the driver disk. If the device has already been installed, the computer activates it and starts talking to it. USB devices can be connected and disconnected at any time. Many USB devices come with their own built-in cable, and the cable has an “A” connection on it. If not, then the device has a socket on it that accepts a USB “B” connector.
The USB standard uses “A” and “B” connectors to avoid confusion:
Fig OF A typical “A” connection Fig OF Typical “B” connection
- “A” connectors head “upstream” toward the computer.
- “B” connectors head “downstream” and connect to individual devices.
By using different connectors on the upstream and downstream end, it is impossible to ever get confused — if you connect any USB cable’s “B” connector into a device, you know that it will work. Similarly, you can plug any “A” connector into any “A” socket and know that it will work.
BIOS & CMOS
Introduction: All motherboards must have a special chip containing software called the ROM BIOS or BIOS. BIOS stand for Basic Input Output System. BIOS in most PCs has four main functions
POST (Power-On Self Test): The POST tests your computers processor, memory, chipset, video adaptor, Hard disks, Floppies, keyboard and other important components.
Bootstrap Loader: A routine that finds the operating system and loads it in RAM.
BIOS- Basic Input Output System: This refers to the collection of drivers for the various hardware components attached to the computers.
CMOS setup : This is normally a menu driven program that allows you to configure the motherboard and chipset settings, along with date and time, passwords, disk drives, and other basic system settings. Some older PC’s cannot co-operate with all the modern hardware because their BIOS doesn’t support that hardware. The operating system cannot call a BIOS routine to use it; this problem can be solved by replacing your BIOS with a newer one, that does support your new hardware, or by installing a device driver for the hardware.
Bootstrap loader
Definition: A routine that finds the operating system and loads or boots it. If an operating system is found it is loaded and given control of your computer This program doesn’t have the full functionality of an operating system, but is tailor-made specifically so that it is capable of loading enough other software for the operating system to start. Often, multiple-stage boot loaders are used, in which several small programs summon each other, until the last of them loads the operating system. The name bootstrap loader comes from the image of one pulling oneself up by one’s bootstraps This program doesn’t have the full functionality of an operating system, but is tailor-made specifically so that it is capable of loading enough other software for the operating system to start. Often, multiple-stage boot loaders are used, in which several small programs call upon each other, until the last of them loads the operating system. Boot loaders may face peculiar constraints, especially in size; for instance, on the IBM PC and compatibles, the first stage of boot loaders is always 512 bytes in length and ends with the AA55h value (which the BIOS looks at to ensure that it is a proper boot loader).
Second-stage boot loader
The small program is most often not itself an operating system, but only a second- stage boot loader, such as NTLDR, LILO or GRUB. It will then be able to load the operating system proper, and finally transfer execution to it. The system will initialize itself, and may load device drivers and other programs that are needed for the normal operation of the OS.
Booting
In computing, booting is a bootstrapping process that starts operating systems when the user turns on a computer system. A boot sequence is the set of operations the computer performs when it is switched on which load an operating system. In modern PC machines the way a computer boots is roughly:
1. A BIOS,stored in ROM, contains the program that checks the disk drives for a MBR.
2. The program found at the MBR is the boot loader which is specific to the OS being booted.
3. The boot loader finds the OS and prepares the hardware for starting the OS.
4. The OS finishes initializing itself then starts optional services and
device drivers before the machine begins to respond to normal input. In the case of a network boot, where a machine may be diskless, the sequence is essentially the same, but the BIOS is in the ROM of a network card which fetches the boot loader program from the network. The boot process is considered complete when the computer is ready to interact with the user or the operating system is capable of running ordinary applications. Typical modern PCs boot in about a minute (of which about 15 seconds are taken by the preliminary boot loaders, and the rest by the one loading the operating system), while large servers may take several minutes to boot and to start all services - to ensure high availability, they bring up some services before others. Most embedded systems must boot almost instantly — for instance, waiting a minute for the television to come up is not acceptable. Therefore they have their whole operating system in ROM or flash memory, so it can be executed directly.
Configuration of system through BIOS
Installing Different Operating systems like DOS and Windows
Introduction :
Operating system: It is a software which allows the users to use computers. Without OS a computer is a mere machine, which is incapable of performing any
work.
Ex : DOS, Windows 9x, Linux, OS/2 , Solaris etc
DOS is one of the oldest operating system. It forms the basis for next generation
of operating systems, like Windows 9x.
Hard Disk Partitions
This procedure explains how to setup a new hard disk. Warning - if you are
setting up a hard disk which contains data, the following procedure wouldcompletely erase your hard disk and the data would be unrecoverable. Before a new hard disk can be used it needs to be setup. This involves partitioning and formatting the hard disk. Windows 98 or ME boot disk contains the required software to perform this procedure. FDISK.EXE and FORMAT.COM are the files required in your bootable floppy disk. Start the partition and format procedure by booting your PC using a Windows boot disk. Make sure you set the BIOS so that the boot sequence is set to detect the floppy disk first. If your system has no problems booting you will be presented with a Windows boot disk menu. This gives you the option to start the system with or without CD-ROM support. At this stage you do not need the CD-ROM support, so choose the option to boot without CD-ROM support. You should end up in the MS DOS prompt A: (A drive).
From A: command prompt type fdisk. You will be presented with following message:
Choose “Y” to enable large disk support.
You will now be presented with the FDISK main menu as shown below. From the menu, choose option 1 - Create DOS partition or Logical DOS drive. Another menu will present the following options.
Choose option 1 - Create primary DOS Partition. FDISK verifies the integrity of your drive and will ask you if want to use the maximum available size of your hard disk to create the primary partition and set it active. To keep things simple we will create one large partition. Choose “Y” to use maximum available space. When the partition has been created successfully you will be notified by the system. Your drive is now known as C: (C drive). Press “Esc” to return to the menu. Press “Esc” again to exit FDISK. You need to restart your system for the changes to take affect. Leave boot disk in the drive. When the system reboots, choose start without CD-ROM from the boot disk menu. While booting from floppy disk you might get error message like “Invalid media type reading drive C” this is OK for this stage as the hard disk is not formatted. If you want to create extended DOS partitions, specify the size of the partitions in the bytes for primary partition. And remaining space can be utilized to create
logical drives in the extended partition. Like D, E , F etc. From A: command prompt type format c: You will get a message saying “WARNING, ALL DATA ON NONREMOVABLE
DISK DRIVE C: WILL BE LOST. Proceed with Format (Y/ N)?”. Don’t worry about the message as you do not have any data in the new hard disk. Choose “Y”. The format will proceed and would show you a progress
Name : Installing different operating systems like DOS and Windows
indicator. The time it takes to format a hard disk depends on the size and speed
of the drive. This could be around 5-30 minutes. Once the format is complete
you need to reset your system. You are now ready to install an operating system
DOS Installation
1. Run Z:\INSTALL
2. Read Copyright agreement
3. Click on OK
4. Choose the hard drive on which you want to install the program and click on NEXT
5. Choose the directory (Default \BIBLE) and click on NEXT
6. Click on INSTALL DATA FILES TO HARD DRIVE and click on NEXT
7. Click on MS-DOS and click on NEXT
8. Click on each versions you wish to install, ensuring that it is highlighted. Click on the right-hand arrow and repeat procedure for each version you wish to install. Use the scroll bar on the right to viewall available versions. Please note that you are restricted to a maximum of nine versions under DOS. When you have completed your choices, click on NEXT
9. Repeat the above procedure with the Notes. You are restricted to eight Notes under DOS. When you have completed your choices, click on NEXT
10. Repeat the procedure for the Topics. When you have completed your choices, click on NEXT Click on FINISH to complete the installation
· Viruses
They’re the common cold for computers; we’ll show you how they
operate and how to protect your PC.
Virus: A virus is just a computer program.
any other program, it contains instructions that tell your computer what to do. But unlike an application, a virus usually tells your computer to do something you don’t want it to do, and it can usually spread itself to other files on your computer—and other people’s computers.
What is a virus?
A virus is a malicious piece of software with the following characteristics. It is: Hidden : You cannot see it with the normal DIR command. Self-Replicating : It automatically copies itself, thus infecting other files and disks. Delayed action : Thus you won’t know you’ve got it until you have been infected for a considerable time, possible with your backups also infected. They can spread very fast across open networks such as the Internet, causing billions of dollars worth of damage in a short amount of time. These software “pranks” are very serious; they are spreading faster than they are being stopped, and even the least harmful of viruses could be life threatening. For example, in the context of a hospital life- Support system, a virus that “simply” stops a computer and displays a message until a key is pressed, could be fatal. Further, those who create viruses cannot halt their spread, even if they wanted to. It requires a determined effort from computer users to be “virus-aware”, rather than continuing the unawareness that has allowed computer viruses to become such a problem. Five years ago, very rarely computers used to get infected by virus i.e once in a year, where as the chance you receive a virus today is increased.
Most common entry points :
The first question that you should ask yourself is: How do viruses get into a computer, or attack it? If you know the answer to this question you can prevent infection by protecting these possible virus entry-points.
The most common entry-points used by viruses are the following:
· Removable disk drives
· Computer networks
· Internet
- E-mail
- Web pages
- File Transfers (FTP)
- Downloads
- Newsgroups
Types of Viruses:
1. Worms:
Worms are different to other viruses since they do not infect other files. Their sole objective is to propagate or spread to other systems as quickly as possible. They do however make use of replication (propagation) techniques. In fact, their objective is to copy themselves and then infect other systems. Their infection or replications usually take place through e mails, computer networks and Internet IRC Channels. They could also replicate inside the memory of a PC.
Trojan Horses (or Trojans):
Trojans cannot be considered viruses as such. They take their name from Greek mythology (the famous wooden horse in which Greek soldiers hid so that they could enter the city of Troy undetected and then attack it). Trojans work in similar way. They seem to be harmless programs which get into a computer through any channel. When that program is executed (they have names or characteristics which trick the user into doing so), they install other programs on the computer which could be harmful.
Logic Bombs:
These activate and damage an infected system only when one or more condition/ s are met. They are not considered viruses as such, since they do not replicate, but rather depend on the actions taken by the user (the user usually copies and / or executes them unintentionally).
Encrypted:
Rather than a virus category, this is a technique that viruses could use. A virus could belong to another category and be also encrypted (if it uses this technique).The virus encodes or encrypts itself so that antivirus programs cannot easily detect it. In order to perform these activities, the virus de-encrypts itself and, when it is finished, encrypts itself again.
Polymorphic:
These are virus that use a new technique to avoid detection by antivirus programs (they are usually the hardest viruses to find). They change with every infection they carry out. In this way, they create a large number of copies of themselves.
Symptoms of Virus
It may appear that you have a virus in your computer, but you cannot be sure that this is the case until it is detected using an antivirus tool (programs that detect and eliminate viruses).Some actions that can be carried out by a virus are obvious enough to be recognized and could include: messages displayed onscreen,operations slowing down, the properties of some files change, files and/or folders disappear, the computer will not start, the content of the infected disk is lost, etc.
What do virus infect.
The main targets of viruses are files located in storage devices such as hard andfloppy disks. They target program files, although other types of files and documentscan alsobeinfected. A program is simply a file with an EXE or COMextension, which can be run to perform specific operations.As we have already mentioned, there are viruses designed to infect files that are not programs. However, these documents contain elements known as macros. Macros are small programs that the user can include in certain types of files. Other elements prone to virus attack are the storage devices themselves, especially boot sector. By attacking the places in which files are stored, the damage produced by the virus will affect all of the information they contain.
