What is Registers? Types of Registers

Register :-

Register are used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU, there are various types of Registers those are used for various purpose. Among of the some Mostly used Registers named as AC or Accumulator, Data Register or DR, the AR or Address Register, program counter (PC), Memory Data Register (MDR) ,Index register,Memory Buffer Register.

These Registers are used for performing the various Operations. While we are working on the System then these Registers are used by the CPU for Performing the Operations. When We Gives Some Input to the System then the Input will be Stored into the Registers and When the System will gives us the Results after Processing then the Result will also be from the Registers. So that they are used by the CPU for Processing the Data which is given by the User. Registers Perform:-

 

1)    Fetch: The Fetch Operation is used for taking the instructions those are given by the user and the Instructions those are stored into the Main Memory will be fetch by using Registers.

 

2)    Decode: The Decode Operation is used for interpreting the Instructions means the Instructions are decoded means the CPU will find out which Operation is to be performed on the Instructions.

 

3)    Execute: The Execute Operation is performed by the CPU. And Results those are produced by the CPU are then Stored into the Memory and after that they are displayed on the user Screen.

 

                                                Types of Registers are as Followings:                                                                                      

MAR stand for Memory Address Register

 

This register holds the memory addresses of data and instructions. This register is used to access data and instructions from memory during the execution phase of an instruction. Suppose CPU wants to store some data in the memory or to read the data from the memory. It places the address of the-required memory location in the MAR.

 

Program Counter

 

The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register

It is a 16 bit special function register in the 8085 microprocessor. It keeps track of the the next memory address of the instruction that is to be executed once the execution of the current instruction is completed. In other words, it holds the address of the memory location of the next instruction when the current instruction is executed by the microprocessor.

 

Accumulator Register

This Register is used for storing the Results those are produced by the System. When the CPU will generate Some Results after the Processing then all the Results will be Stored into the AC Register.

 

Memory Data Register (MDR)

MDR is the register of a computer's control unit that contains the data to be stored in the computer storage (e.g. RAM), or the data after a fetch from the computer storage. It acts like a buffer and holds anything that is copied from the memory ready for the processor to use it. MDR hold the information before it goes to the decoder.

 

MDR which contains the data to be written into or readout of the addressed location. For example, to retrieve the contents of cell 123, we would load the value 123 (in binary, of course) into the MAR and perform a fetch operation. When the operation is done, a copy of the contents of cell 123 would be in the MDR. To store the value 98 into cell 4, we load a 4 into the MAR and a 98 into the MDR and perform a store. When the operation is completed the contents of cell 4 will have been set to 98, by discarding whatever was there previously.

 

The MDR is a two-way register. When data is fetched from memory and placed into the MDR, it is written to in one direction. When there is a write instruction, the data to be written is placed into the MDR from another CPU register, which then puts the data into memory.

 

The Memory Data Register is half of a minimal interface between a micro program and computer storage, the other half is a memory address register.

 

Index Register

A hardware element which holds a number that can be added to (or, in some cases, subtracted from) the address portion of a computer instruction to form an effective address. Also known as base register. An index register in a computer's CPU is a processor register used for modifying operand addresses during the run of a program.

 

Memory Buffer Register

MBR stand for Memory Buffer Register. This register holds the contents of data or instruction read from, or written in memory. It means that this register is used to store data/instruction coming from the memory or going to the memory.

 

Data Register

A register used in microcomputers to temporarily store data being transmitted to or from a peripheral device.




Chapter : Memory & Input/Output Unit

• Computer Fundamental 

Input and Output Devices

The devices which are used to input the data and the programs in the computer are known as "Input Devices". or  Input device can read data and convert them to a form that a computer can use. Output Device can produce the final product of machine processing into a form usable by humans. It provides man to machine communication. Some of the I/O devices are explained below:

 

(1) Keyboard : Keyboard is used in the input phase of a computer-based information system. Keyboard is most common input device is used today. The data and instructions are input by typing on the keyboard. The message typed on the keyboard reaches the memory unit of a computer. It’s connected to a computer via a cable. Apart from alphabet and numeral keys, it has other function keys for performing different functions.

 

(2) Mouse : It’s a pointing device. The mouse is rolled over the mouse pad, which in turn controls the movement of the cursor in the screen. We can click, double click or drag the mouse. Most of the mouse’s have a ball beneath them, which rotates when the mouse in moved. The ball has 2 wheels of the sides, which in turn mousse with the movement of the ball. The sensor notifies the speed of its movements to the computer, which in turn moves the cursor/pointer on the screen.

 

(3) Scanner : Scanners are used to enter information directly in to the computers memory. This device works like a Xerox machine. The scanner converts any type of printed or written information including photographs into digital pulses, which can be manipulated by the computer.

 

(4) Track Ball : Track ball is similar to the upside- down design of the mouse. The user moves the ball directly, while the device itself remains stationary. The user spins the ball in various directions to effect the screen movements.

(5) Light Pen : This is an input device which is used to draw lines or figures on a computer screen. It’s touched to the CRT screen where it can detect raster on the screen as it passes.

 

(6) Optical Character Rader : It’s a device which detects alpha numeric characters printed or written on a paper. The text which is to be scanned is illuminated by a low frequency light source. The light is absorbed by the dark areas but reflected from the bright areas. The reflected light is received by the photocells.

 

(7) Bar Code Reader : This device reads bar codes and coverts them into electric pulses to be processed by a computer. A bar code is nothing but data coded in form of light and dark bars.

 

(8) Voice Input Systems : This devices converts spoken words to M/C language form. A micro phone is used to convert human speech into electric signals. The signal pattern is then transmitted to a computer when it’s compared to a dictionary of patterns that have been previously placed in a storage unit of computer. When a close match is found, the word is recognized.

 

(9) Plotter : Plotter is an O/P device that is used to produce graphical O/P on papers. It uses single color or multi color pens to draw pictures as blue print etc.

 

(10) Digital Camera : It converts graphics directly into digital form. It looks like an ordinary camera, but no film is used therein, instead a CCD (changed coupled Divide) Electronic chip in used. When light falls, on the chip though the lens, it converts light waves into electrical waves.

 Chapter : Memory & Input/Output Unit

• Computer Fundamental

What is FPU (math coprocessor)?

FPU stands for floating point unit, a small chip built into some computers. Sometimes referred to as a math coprocessor or a math chip, an FPU can calculate complex mathematical problems and various graphic tasks much faster than the "general purpose" CPU (central processing unit) found in all computers. It's called a floating point unit because its speed really shows when calculating equations involving numbers having decimal portions, such as 67.9345x 0.00345. 



Chapter : Introduction to Computer

• Computer Fundamental 

What is Density?

Density reflects the closeness of data on a disk: the closer the data is, the denser a disk is said to be. Of course, when data is placed closer together (more densely), a disk can store more data. Floppy disks, which are magnetic data storage devices, come in two commonly used sizes: 3.5-inch and 5.25-inch. Both sizes are available in two densities: double- density and high-density. Inside a floppy disk is a thin piece of film with a magnetic coating. The magnetic coating is where data is stored. Density refers to the amount of magnetic particles in the coating.

Regardless of the size of the particle, it can only store one piece of data. A high-density disk has smaller magnetic particles, which allows more particles to fit on a disk, and makes it possible for the disk to store more data. A double-density disk has larger particles that are not so tightly packed; therefore, it holds less data. (A hard disk, by the way, uses a different type of magnetic material that is much denser than the magnetic material used on any floppy disk. This allows a hard disk to hold a lot more data.)

A 3.5-inch double-density disk can hold 720 kilobytes of data. A 3.5-inch high-density disk can hold 1.44 megabytes of data. A 3.5-inch disk can only be used in a 3.5-inch floppy disk drive. A 5.25-inch double-density disk can hold 360 kilobytes of data, and a 5.25-inch high-density disk can hold 1.2 megabytes. A 5.25-inch disk can only be used in a 5.25-inch floppy drive. It is also important to know what type of density the floppy drive is made to handle. Most new disk drives are high-capacity drives, and can handle both high-density and double-density disks. However, older drives were low-capacity and can only handle double-density disks. 

Chapter : Introduction to Computer

• Computer Fundamental

What is Dual Floppy Drive?

A computer with a dual floppy drive has two slots in which to insert a floppy disk. Although several years ago this meant you simply had two of the same kind of floppy drives so you could work from two different disks, it now usually means that one of the drives will take a 3.5-inch high-density floppy disk, and the other will take a 5.25-inch floppy disk.

Chapter : Introduction to Computer

• Computer Fundamental 

What is Docking Station?

A docking station is a unit that attaches to a laptop or notebook computer, either directly or by cable, providing the laptop with more hardware. This arrangement increases the laptop's capabilities almost to that of a standardized desktop computer. A docking station typically includes standard expansion slots, as well as additional ports (sockets) for connecting a printer, modem, keyboard, etc. So if you have a laptop computer and a docking station, you can take your laptop with you wherever you go, accepting its limitations as a laptop. Then when you come home or go back to the office, you can connect your laptop to the docking station (with some units this is like inserting a giant video tape into a VCR). Then your laptop virtually turns into a regular desktop computer, complete with large monitor, large hard disk, more RAM, etc

Chapter : Introduction to Computer

• Computer Fundamental 

What is Bus Snooping?

Bus Snooping: A mechanism for maintaining CACHE COHERENCY in MULTIPROCESSOR computers, under which each cpu's cache-control logic watches the external memory bus, looking for reads or writes made by other processors (that is, it 'snoops' on their transactions). Whenever such a transaction is detected, the cache logic enquires whether a copy of the target address exists in its own cache, and if so either writes that line back to memory or declares it invalid.

Chapter : Introduction to Computer

• Computer Fundamental 

What is backside bus?

A second PROCESSOR BUS built into high-performance microprocessors, such as the PENTIUM II and later, used to connect the processor to its LEVEL 2 CACHE memory so that the latter does not have to share the bandwidth of the ordinary I/O bus with main memory accesses.

Chapter : Introduction to Computer

• Computer Fundamental

What is Dumb Terminal?

A terminal consists of a screen and keyboard which allow you to interact with a multi-user computer; the computer itself is often located in another room or even a different building. A dumb terminal, which is the most common type of terminal, has no computing capabilities of its own. You enter commands on the terminal's keyboard to tell the computer what to do, and the computer sends messages back to you on the terminal's screen. The computer does all the work (of running programs, for example), with no help from the dumb terminal.

Chapter : Introduction to Computer

• Computer Fundamental

What is Bus Master?

Bus Master: Any device within a computer that is capable of taking control of the BUS and initiating data transfers with the memory and PERIPHERALS (which are slave devices and can only respond passively to access attempts). In simple systems the CPU is the only bus master, but in others such as the PC I BUS, there may be multiple masters: for example it is common for a SCSI disk controller to be granted bus master status so that it can transfer data to and from memory without CPU involvement.

Chapter : Introduction to Computer

• Computer Fundamental

What is Parallel Computer?

A computer with multiple processors that can all be run simultaneously on parts of the same problem to reduce the solution time. The term is nowadays mostly reserved for those MASSIVELY PARALLEL computers with hundreds or thousands of processors that are used in science and engineering to tackle enormous computational problems.There are two fundamental divisions in parallel computer architecture. The first is between those architectures in which each processor has it own memory space and communicates with others by MESSAGE PASSING, and those architectures in which all the processors communicate through a shared memory (SHARED-MEMORY MULTIPROCESSORS). The increasing number of high-end PCs and servers that contain more than one processor fall into this latter category.

The other fundamental division is between those computer architectures in which each processor executes the same program on a different data item (SINGLE-INSTRUCTION MULTIPLE-DATA or SIMD)and those in which each processor executes a different program (MIMD or multiple-instruction multiple-data). Within these subdivisions, the processors can be connected together in many different ways (their TOPOLOGY) which profoundly affect the efficiency of communication between them. 

 Chapter : Introduction to Computer

•  Computer Fundamental

  

What is (floppy disk, high density) FDHD?

FDHD stands for floppy disk, high density and refers to the floppy disk drive in current Macintosh models. This drive can read and write single sided disks (400K), double-sided disks (800K), and high-density disks 0.2 megabytes). It can also understand 3.5" Dos-formatted disks from IBM PCs and Apple II machines. An FDHD is also known as a SuperDrive.

 Chapter : Introduction to Computer

•  Computer Fundamental

What is bus width?

If you think of the computer's bus as being a freeway that carries data, then it is easy to visualize the bus width as the number of lanes on this freeway. Naturally, the more lanes available, the more data that can be carried at any given moment. Bus widths are generally designated in multiples of eight; a 32-bit bus width has the capability to carry four times the information of an 8-bit bus in the same amount of time.

  Chapter : Introduction to Computer

• Computer Fundamental

What is Bus Locking?

Bus Locking: A type of BUS architecture in which some particularly bandwidth-hungry device, for example a GRAPHICS PROCESSOR, is permitted to keep control of a computer's bus for many successive cycles to the exclusion of other devices. It was employed in some early Apple MACINTOSH systems to improve graphics throughput, but would be frowned on in today's highly multitasking, multiprocessor environments.

Chapter : Introduction to Computer

• Computer Fundamental

What is PDA (personal digital assistant)?

PDA stands for personal digital assistant, a term for a new breed of handheld computers. PDAs are supposed to combine the power and flexibility of a real computer with the convenience of those little electronic organizers- the kind made by Sharp and Casio-that let you keep track of your names and addresses and to-do items.A PDA can run much more complex software than an electronic organizer, and you're not stuck with the built in software-you can buy separate programs to customize the PDA to your specific tasks. With many PDAs you can use a stylus to write on the little screen. The PDA most people are talking about is the Newton, made by Apple, but many other companies are planning their own versions.

Chapter : Introduction to Computer

• Computer Fundamental

What is Analytical Engine?

 The Analytical Engine, designed by Charles Babbage between 1833 and 1846, anticipated many features of electronic computing devices invented in the 1940s and 1950s. Although mechanical in all its operations, the Analytical Engine could carry out calculations of arbitrary complexity under the control of punched cards. Conditional branching was possible, and Babbage had prepared test programs that included elaborate calculations based on nested loop structures. In a beautiful anticipation of twentieth-century thinking, Babbage showed that, given sufficient time, any finite calculation could be carried out by the Analytical Engine.

 Chapter : Introduction to Computer

•  Computer Fundamental

What is expansion bus or Microcomputer Buses?

On a microcomputer, the bus is usually called anexpansion busbecause its design determines the degree to which the minimum configuration of the system can be expanded with regard to memory, processing speed, graphics capability, and peripheral support. The expansion bus is the collection of wires, paths, connectors, and controllers responsible for distributing the data and instructions from the microprocessor to the peripheral expansion cards.Slotsconnected to the bus provide places to plug those cards in, and the bus then provides a mechanism for communicating with them.In modern designs the expansion bus is not normally the same bus that the CPU uses to access MAIN MEMORY, as the contention this would cause could slow the whole system down. Expansion cards may also be allowed to use DIRECT MEMORY ACCESS to avoid involving the CPU in most of their memory operations.

Examples of expansion buses include the ISA BUS and PCI BUS in the PC world, the VMEBUS for UNIX systems and the NUBUS for the Apple MACINTOSH.

Chapter : Introduction to Computer

• Computer Fundamental 

Bad Sector

                       What is bad sector?

A disk has two sides (a top and a bottom). Each side of the disk has tracks or concentric rings on the surface. Each ring is divided like a pie into equal wedges, or sectors, which are the smallest units of storage space on the disk. If one of these units is damaged or flawed, it is considered a bad sector and cannot be used.

If there was already data in that sector when it got damaged, chances are slim that you can recover that data unless you have the specialized hardware and software necessary for that sort of operation. Almost all hard disks are born with bad sectors, so don't freak out if your software utility reports them. Other bad sectors should not start appearing, though, after you start using the disk.

 Chapter : Introduction to Computer

•  Computer Fundamental

Bus Speed

                      What is Bus Speed? 

Bus Speed: The rate at which a computer's PROCESSOR BUS can transmit data, which is a crucial determinant of its overall performance. The bus speed of most personal computers remained at 33 MHz for a decade, only recently being increased to 100 MHz, and technologies such as the two-level processor CACHE, DIRECT MEMORY ACCESS or the Accelerated GRAPHICS PORT can be seen as ways to surmount this restriction by bypassing the processor bus.

Chapter : Introduction to Computer

• Computer Fundamental 

16-bit Slot

                       What is 16-bit Slot? 

 

Slot One type of socket fitted to a computer's MOTHERBOARD into which expansion cards can be plugged.

pcs have several different types of slots. The slots can also act as input/output ports for attaching external devices (such as digital cameras) via a cable. The slots in the original IBM PC could transfer only 8 bits of information at a time between the motherboard and the card in the slot; these are 8-bit slots. The PC/AT was the first PC to have 16-bit slots, and set the standard still followed by most pcs today (see lSA and bus). The 16-bit slots actually have two separate slots arranged in a line; the slot toward the back of the computer is exactly the same as an 8-bit slot.

In other words, you can plug an 8-bit add-in board into a 16-bit slot (but not the other way around, of course). EISA slots are 32-bit slots which accept standard 8-bit and 16-bit boards, as well as special 32-bit boards. Then there are the 32-bit Micro Channel slots, which take only Micro Channel boards. See also full-length slot.

Chapter : Introduction to Computer

• Computer Fundamental 

CISC architecture or CISC chips

    What is CISC architecture or CISC chips? 

ClSC (pronounced "sisk") stands for complex instruction set computing. A CISC chip is a microprocessor that has a large set of instructions that are built into its microcode so it can carry out most computations directly. Compare CISC chips with RISC chips, which recognize fewer instructions. CISC term applied to all the older computer ARCHITECTURES to distinguish them from the new RISC designs introduced in the 1990s. RISC (reduced instruction set computing) technology is touted as faster than CISC and is increasingly common, although there is a great deal of debate over the pros and cons of each type of architecture.

A CISC INSTRUCTION SET contains instructions that perform several steps in one, and therefore take many CYCLES to execute - such as the Intel 8086's ADC instruction, which takes more than 20 cycles to add the contents of a REGISTER to a memory location. The concept grew through the early days of computing from a desire to make life easier for MACHINE CODE programmers, but now that most programming is done in HIGH-LEVEL languages it is less necessary and hinders hardware efficiency. RISC designs employ a larger number of simple, one cycle operations that are automatically generated by a COMPILER.

Chapter : Introduction to Computer

• Computer Fundamental 

Bus Cycle

                        What is Bus Cycle?

Bus Cycle: The sequence of primitive operations for transferring each item of data over a computer's BUS, which are performed in time with the system CLOCK SIGNAL. Each bus cycle may take several clock cycles, and may be either a READ or WRITE cycle depending on the direction of data transfer. The steps for a read cycle might be:

1.Request control of the bus.

2. When granted, place target address on bus.

3.Receivedata from bus.

4. Release bus.

Different bus PROTOCOLS employ variants and enhancements to this simple schema, for example possibly transferring more than one data item per cycle.

Chapter : Introduction to Computer

• Computer Fundamental 

 

Address bus

                                     What is address bus? 

 The BUS upon which a computer's CENTRAL PROCESSING UNIT issues addresses to the memory system in order to read or write a word of data. In some system architectures, the data word itself may be transported via a separate DATA BUS.




Chapter : Introduction to Computer 

•     Computer Fundamental 

Address generation

                      What is address generation? 

 An operation that calculates the address of the next instruction or piece of data required, performed within the CENTRAL PROCESSING UNIT of a computer.

Chapter : Introduction to Computer

• Computer Fundamental 

File format

                            file format

A file format refers to the particular structure that a document (also called a "data file") is stored in, whether it contains graphics, text, a spreadsheet, etc. For instance, in a word processing document, the file format would include the codes that represent each character; the codes for creating the text styles, such as italic or bold; and information such as the type of application the document was created in.

Each program has its own way of storing this information-its own file format. The MacWrite format is different from the Word format which is different from the WordPerfect format. To use a document created by another application, the program has to convert the foreign format into its own "native" format.

In addition to native file formats for every word processor, there are generic text file formats, such as ASCII (text-only) or RTF (rich text format). There are many different file formats for graphics, as well, such as TIFF, PICT, PCX, MacPaint, WMF, DRW, EPS. Different programs can use different formats, and many programs can open and use more than one.


Chapter : Introduction to Computer 

• Computer Fundamental 

Minicomputer

                              What is Minicomputer?  

A minicomputer isn't very mini. At least, not in the way most of us think of mini. You know how big your personal computer is and its related family. A workstation is the next step up in size, performance, and price, and is similar to a personal computer in that it is used by one individual.

Then comes the minicomputer. A minicomputer costs from $20,000 to $200,000 or so. It is built to perform different tasks for different people at the same time. Each person using a minicomputer has their own terminal attached by wires or via a modem to the computer proper. (A terminal isn't a computer-it's basically just a keyboard and a monitor; see the full definition.) The minicomputer spends a little bit of time on one person's task, then moves on to the next, and so on, juggling the work based on which jobs it thinks are most important. If you're the only one using a minicomputer, this can be one fast machine.

But once many users (people) are "on" the system, the thing begins to slow down-you may type something and then wait for a minute or more before you see a response on the screen. Minicomputers used to be the only option for companies. Now, many firms are turning to networks of personal computers to accomplish the same thing faster and cheaper.


Chapter : Introduction to Computer

• Computer Fundamental 

 

Access time

                               What is access time? 

  Access time refers to how fast the disk or memory can locate and begin retrieving (accessing) a specific piece of information or transfer data to the CPU. A low access time indicates a fast hard drive. Access time is measured in milliseconds, or ms. when making comparisons, look for 'memory access time' (measured in nanoseconds), Memory access time refers to the time it takes to transfer a character from memory to or from the processor, and/or 'disk access time' (measured in milliseconds) refers to the time it takes to place the read / write heads over the requested data. Sometimes the speed of a disk drive is measured by the rate at which it transfers data - in this case, a higher' data transfer rate' indicates a faster drive. For a disk drive the access time includes both the head SEEK TIME and the LATENCY.

For a disk, total access time is the sum of seek and rotational times to reach a particular record. RAM may have an access time of 80 nanoseconds or less, while hard disk access time could be 18 milliseconds or less.

For a floppy drive, the average access time is 25 ms; the access times for CD-ROMs approximately twice as long as for floppy disks.

For a drum or fixed-head disk, average access time is a half-revolution and maximum access time is a full revolution, since both have heads that are fixed over the data areas. Average access times for drums are 5 to 10 ms.


Chapter : Introduction to Computer

• Computer Fundamental 

Coprocessor

                                      What is coprocessor?  

A coprocessor is a chip that works side-by-side with the computer's main processor (the chip called the central processing unit, or CPU). The coprocessor handles some of the more specialized tasks, such as doing math calculations or displaying graphics on the screen, thereby taking some of the work load off the main processor so it can go on with the business of directing and keeping order over the whole show. A coprocessor is installed to reduce the burden on a computer's CPU and thus free it for more general duties such as transferring data and handling multiple tasks. 

Math coprocessors, for example, are specialized for performing calculations on numbers, and they are much faster at it than the main processor in your computer. So if you have a program that does many math calculations, such as a spreadsheet or a CAD program, then adding a math coprocessor to your system can sometimes remarkably improve your computing speed.

There are video coprocessors that are used to speed up the display of graphics on your screen. Again, if you use any graphics-based application, including Windows, then adding a video coprocessor to your system on an add-in board can speed up your system even more than buying a faster computer.

One catch, however, with any kind of coprocessor, is that the software you use must be written so that it knows the coprocessor is there, otherwise your system will not recognize its existence and won't be able to use it.

A coprocessor may be designed to work just with a particular type of CPU, in which case its instructions can be included in the main program and are passed on to the coprocessor by the CPU as it encounters them. In other cases, the coprocessor may require its own separate program and program memory, and communicates with the CPU by interrupts or message passing via a shared memory region.




Chapter : Introduction to Computer

• Computer Fundamental 

32-bit addressing

                         What is 32-bit addressing?  

If a computer uses 32-bit addressing, that means the address can have 32 numbers. With the possibility of each number being either a one or a zero, there are 4 billion different addresses available (232). Four billion bytes (each memory location holds one byte) is 4,096 megabytes, which is 4 gigabytes. So with 32-bit addressing you can theoretically address 4 gigabytes of memory.

Alas, at this point in technology there are still some limitations in the hardware, so you can't really install and use (address) all 4 gigabytes. A PC with an 80386 or 80486 microprocessor can address 4 gigabytes of memory all right, but they don't make PCs that can hold that many memory chips. The most a modular Mac (any of the Mac II family) can address is "only" 128 megabytes, and some of the Quadra’s can go up to 256 megabytes.

 

 

Chapter : Introduction to Computer

• Computer Fundamental 

AUTOEXEC.BAT File

                       What is AUTOEXEC.BAT File?  

The name of this batch file comes from a combination of the words automatically executed batch file. Like other batch files, AUTOEXEC.BAT contains a series of DOS commands that your (IBM-compatible) PC runs for you, one after the other, so that you don't have to type the commands individually. It gives the computer various basic instructions about starting Windows, running antivirus checks in the background, identifying the keyboard, and so on.

The file was typically used to issue configuration and initialization commands to the operating system and PERIPHERAL devices such as CD-ROM drives and sound cards, a typical entry being. What's special about AUTOEXEC.BAT is just that DOS automatically runs this particular batch file each time you turn on or restart the computer. Most people wind up calling AUTOEXEC.BAT the "AUTOEXEC" file for short.

AUTOEXEC.BAT must be stored in the ROOT DIRECTORY of the computer's BOOT DRIVE in order to be found and executed, and the commands it contains follow the same syntax as any other MS-DOS BATCH File, that is, a list of operating system commands exactly as they would be typed manually at the COMMAND PROMPT, plus certain control structures such as GOTO that cannot be deployed manually.

You can customize the AUTOEXEC file yourself, filling it with exactly the commands you want to get your system up and running to your specifications and to suit the needs of your software and peripherals. AUTOEXEC.BAT is typically used to set the look of the DOS prompt, tell DOS which directories it should search when looking for programs to run, configure the serial ports, load the mouse driver, and start memory resident programs and utilities. If you like, you can use the AUTOEXEC file to start a particular application program (such as your word processor) or to start Windows.

Here's an excerpt from a typical AUTOEXEC.BAT file:

PROMPT $p$g

PATH=C: \ WINDOWS;C: \DOS;C: \ UTILS

SET TEMP=D: \ TEMP

These lines set the DOS prompt to show the current directory; set the DOS path; and tell the system to look for temporary files in the D: \ TEMP directory.

BOOT

The process of starting or restarting a computer. Boot is a process that the computer goes through to get ready to receive input. During this boot process, certain configuration files, such as the AUTOEXEC.BAT, are used. For example, at startup, the commands in AUTOEXEC.BAT are executed one at a time automatically, without the user typing them in.

BATCH FILE

A type of executable file that contains a "batch" or listing of DOS commands to be executed in order, as if the user had typed each one in separately. One example of a batch file is the AUTOEXEC.BAT, whose instructions are executed whenever the system is booted.

DOS PROMPT

A symbol that indicates DOS is ready for the next command. The DOS prompt generally looks like C:\>, but it can be changed by commands in AUTO.EXEC.BAT.





Chapter : Introduction to Computer

• Computer Fundamental 

 

Mainframe computer

                       What is mainframe computer?  

The term mainframe has shifted from its original reference to the main housing, or frame, that contained the central processing unit (CPU) of the computer. In those days, all computers were big-like the size of a garage-and the frame for the CPU might have been as big as a walk-in closet. Now mainframe refers to the kind of large computer that runs an entire corporation.

While "large" can still mean as big as a room, most of today's mainframes are much smaller, although they're still quite a bit bigger than a personal computer or even a minicomputer. A mainframe has an enormous storage space on disk and tape (like thousands of kilobytes, measured in gigabytes), and an enormous amount of main memory. Theoretically, it works a lot faster than the fastest personal computer. A mainframe also costs big bucks, from half a million or so on up.

Mainframes are tended by special technicians who feed them the programs they run and who scramble around trying to fix them whenever they stop working, which is often. All mainframes are multi-tasking, multi-user machines, meaning they are designed so many different people can work on many different problems, all at the same time.

Mainframes serve most often as information stores and processors. An army of smaller computers is connected to the mainframe. These smaller computers are not in the same room; they may be connected through phone lines across the world. Ordinary people in the company never touch the mainframe itself. Instead, they interact with the computer using a terminal, which is more or less a keyboard and a monitor connected to the mainframe with wires, or by modem over the phone lines. People use the smaller computers and get information from and send information to the mainframe.

The difference between a minicomputer and a mainframe is arbitrary, and different people may use either term for the same machine. Even if you don't work for a large company, you might have contact with a mainframe: when you connect to an online information service or a commercial e-mail service from your personal computer, you are often connecting to a mainframe.

In the '60s the mainframe vendors were called "IBM and the seven dwarfs": Burroughs, Univac, NCR, Control Data, Honeywell, GE, and RCA. They turned into IBM and the BUNCH after Honeywell ate GE's computer division and Univac ate RCA's.




Chapter : Introduction to Computer

• Computer Fundamental 

 

Bus Contention

                               What is Bus Contention?  

Bus Contention: A loss of performance that can arise when two or more devices – for example computer PROCESSORS or disk controllers - try to transfer data simultaneously over the same BUS. For example hesitation may be introduced into a video or audio playback whenever the disk is being accessed. Contention is ameliorated by some kind of ARBITRATION scheme that regulates bus usage in a fair and orderly way, ensuring that all the contending devices are granted access for a reasonable duration and within a reasonable time ..It can be avoided altogether by changing the hardware architecture so as to provide separate buses for each device. 




Chapter : Introduction to Computer

• Computer Fundamental 

Electronic numerical integrator and calculator

                       What is ENIAC (electronic numerical integrator and calculator)?  

ENIAC is an acronym for electronic numerical integrator and calculator. The ENIAC, assembled in 1946, was the first operational digital computer. This monster occupied 1,800 square feet, used 18,000 vacuum tubes, and performed simple addition calculations at a rate of 5,000 per second (very, very slow by today's standards). 






Chapter : Introduction to Computer

• Computer Fundamental 

Supercomputer

                              What is Supercomputer? 

  Supercomputers are the biggest, fastest, and most expensive computers on earth. The cheapest supercomputer costs well over $1 million. They're used for scientific simulations and research such as weather forecasting, meteorology, nuclear energy research, physics and chemistry, as well as for extremely complex animated graphics.

Besides raw speed, one big difference between a supercomputer and a mainframe is that a mainframe serves many people at once or runs several programs concurrently, whereas a supercomputer funnels its power into executing a few programs at high speeds. Mainframes are mostly used for large data storage and manipulation tasks, not for computationally-intensive tasks.






Chapter : Introduction to Computer

• Computer Fundamental 

Microcomputer

                              What is Microcomputer? 

Your personal computer is a microcomputer. Technically, a microcomputer is a computer in which the CPU (central processing unit, the brains of the computer) is contained on one single chip, a microprocessor. Most workstations are also considered microcomputers, for the same reason, although some personal computers are as fast as the fastest workstation. And a computer used by more than one person (a multi-user computer) is still a microcomputer as long as it has a microprocessor for its CPU.

The next step up from a microcomputer On size, speed, capabilities, and price) is a minicomputer. Then a mainframe. Then a supercomputer.






Chapter : Introduction to Computer

• Computer Fundamental 

Batch File

                                  What is Batch File?   

A batch file is a file containing a series of commands that the operating system will carry out for you, one at a time. A batch file is a collection of DOS commands. MS-DOS batch files consist of the normal operating system commands (e.g. DIR, DEL, COPY and MKDIR) together with some extra commands such as IF, FOR, GOTO, SHIFT and PAUSE that provide conditional control of execution and enable PARAMETERS to be passed so that the same batch file can be used in many different contexts. Under UNIX, batch files are called SHELL SCRIPTS, and are written in a c-like scripting language. A batch file, such as WP.BAT, ends with the letters .BAT. When the user types in the name of a batch file and presses Enter at the DOS prompt, the commands in that batch file are performed one at a time-with no additional instructions from the user. For example, if the user typed WP and pressed Enter, WordPerfect (a popular word processing program) would start.

Batch files are great when you use a given set of commands repeatedly-instead of activating each command separately every time you want to carry out that set of commands, you can accomplish the same thing in one step.

A user can create a batch file to perform any routine task. For example, a batch file could be created to prepare a disk for use (a process called formatting). Because the commands are in a batch file, the user doesn't have to type them herself, or even remember what they are-all the user would have to do is type the name of this batch file to format a disk.

The most important batch file is the AUTOEXEC BAT. This file contains commands that are performed automatically each time the PC is turned on or restarted. Typical AUTOEXEC BAT commands include those which change the system prompt, display the current date and time, and set the directories in which DOS looks for files.

Batch files were very important before Windows came along, when everyone had to deal with DOS (the PC's operating system). DOS required the user to type everything in-which made each task tedious and easy to make mistakes. Batch files eliminated mistakes because the user no longer typed in the command, just the name of the batch file. With Windows, there is little typing involved in issuing commands. Instead, the user selects commands from a list called a menu, or he selects an icon that represents the command he wants performed. Automation is still desirable in Windows, but instead of saving a list of typed commands, the user records his actions and saves them in a macro. A macro is like a batch file; when it's activated, the actions recorded in the macro are carried out. 




Chapter : Introduction to Computer

• Computer Fundamental 

 

Hybrid Computers

                     What is Hybrid Computers? 

  During the period from the early 1960s to the early 1970s, electronic analog computers were increasingly combined with a digital computer in hybrid systems. The idea was to combine the easy programmability of a general purpose digital computer with the ability of a large electronic analog computer to solve substantial, complex problems, notably large sets of nonlinear differential equations, or to simulate challenging spaceflights and "person-in-the-Loop" situations in real time. A number of specialty hybrid systems emerged in the mid- to late 1960s and early 1970s. An unusual such system was the Trice digital analog computer developed by the Packard Bell Company and used by NASA for spaceflight simulation.

Chapter : Introduction to Computer

• Computer Fundamental 

How BIOS Works

            How BIOS (Basic Input Output System) Works 

BIOS stand for Basic Input Output System (pronounced "by ose," that's "ose" as in comatose). BIOS are a set of instructions that tell the computer how to handle the flow of information between the computer and its peripherals, such as the keyboard (input) or the printer (output). . The BIOS is firmware, meaning it is a program built into the read-only memory (ROM) in your computer, rather than stored on a disk (because The BIOS is stored in a ROM chip and automatically executed whenever the power is switched on, it's sometimes called the ROMBIOS). Since the ROM BIOS instructions are read-only memory, they cannot be changed. Modern PCs employ FLASH MEMORY rather than ROM to store the BIOS routines so that they can be updated from a floppy disk whenever a new version is released, say to support some newly invented device.  These chips are normally divided into blocks. Each block can be erased and programmed independently. Blocks can also be locked to prevent accidental reprogramming. This ability to program the BIOS after it has been installed forestalls the obsolescence of BIOS chips as new hardware features are installed. In this way the BIOS can be updated by modemor directly from a disketteto bring the code in line with new hardware capabilities.

When you turn on your computer, the BIOS is responsible for checking all the hardware, including memory; it will display an error message if it finds a problem. The BIOS then loads the operating system-whether it's DOS, os/2, Unix, or what have you-into memory from disk. Even after the operating system is running, the BIOS handles many essential chores, putting characters on the screen, getting characters from the keyboard, reading and writing sectors to the floppy or hard disk. You'll see this as your ROMBIOS chip on your computer that works with your software.

One function that BIOS performs happens only when the computer is turned on or restarted (booted). ROM BIOS checks out the computer by performing the power on self test (POST). The computer reads these instructions each time it is turned on and performs a self check of the computer and its components.

The BIOS keeps a store of crucial parameters, such as the number and nature of disks present and the type of PROCESSOR fitted, in a small, separate writeable memory area called the CMOS- one of these settings determines on which disk to look for an operating system. The user can inspect and alter these CMOS settings by holding down certain combination of keys (e.g. function key Fl for some makes of PC) to interrupt the computer's BOOT-UP sequence.

How Does It Work?

When the computer is booted, the CPU activates the ROM BIOS chips. ROM BIOS then begins a series of system checks, called the power on self test (POST). The POST tells the CPU to check the bus (a series of connections that link all of the PC's components), the memory (RAM), the peripherals (keyboard, mouse, etc.), and the disk drives. This system check is fast and not very thorough. The POST determines whether everything is connected properly, but it does not check to see if everything is functioning perfectly. After the POST check is complete, the computer is ready to load the computer's operating system. At this point, a user may notice that the light in drive A comes on again as the CPU checks to see whether a bootable disk has been placed in the drive. If it does not find the operating system software there, the CPU continues to the hard drive, where it copies the operating system into memory so it is ready to go.





Chapter : Introduction to Computer

• Computer Fundamental