Floppy Disk

What is Floppy Disk?

The floppy disk drive  also known as floppy or FDD is the primary removable storage medium for a personal computer. The FDD,once called a mini disk, is the primary medium for getting voluminous information into and out of a micro computer system.  If you have two FDDs of different storage capacities, A: In DOS and Windows the identifier used for the first floppy disk drive; the second floppy disk is designated as drive B:.

A floppy disk, often called a diskette Drive in the PC world, is a thin, round, flat piece of Mylar. It has an extremely thin coating of ferric oxide or magnetic oxide layer that is capable of storing magnetic fields, like thick recording tape. The read-write head in afloppy disk drive stores data on the disk by altering the magnetic particles.

The large, 5.25-inch floppy disks that most PCs use are kept in a paper envelope. The smaller, 3.5-inch floppy that all Macintoshes and some PCs use is enclosed in a rigid plastic case with a sliding metal shutter for head access.

Floppy disks retrieve information far more slowly than HDD because they rotate at lower speed (300 rpm as against 10,000+ rpm).

Data is written on to the floppy disk by the disk drive's read/write heads as the disk rotates inside the jacket.

Because floppy disks store information magnetically, any magnet can destroy the data (information) on the disk. This means you should never allow your floppy disks near a magnetic paper clip holder, the telephone, the stereo, a portable radio, or any other electronic device-and don't pin them to a filing cabinet with a magnet!

IBM Computer used 5.25" inch floppy disks can contain 360 KB, while modern 3.5" inch disks hold 1.44 Mb. Floppy disks became the main medium for software distribution during the formative years of personal computing.

In Floppy Disks, information is organized in tracks. Each track is subdivided into sectors and each sector into bytes. The smaller 3.5" Floppy Disks use 80 tracks per side, 18 sectors per track, and 512 bytes per sector, yielding a capacity of 1.44 MB. Floppy disks first appeared in the late 1960s when IBM used them in an early minicomputer.

The advantage of the floppy disk is that it is removable, and so can be used to distribute software, to transfer data from one computer to another, or to back up files from a hard disk. But compared to a hard disk, floppy disks are also slower, offer relatively small amounts of storage, and can be easily damaged.

What is BUS?

What is BUS?

Bus: The electrically conducting path along which data is transmitted inside any digital electronic device. A bus consists of a set of parallel conductors, which may be conventional wires, copper tracks on a PRINTED CIRCUIT BOARD, or microscopic aluminum trails on the surface of a silicon chip. Each wire carries just one bit, so the number of wires determines the largest data WORD the bus can transmit: a bus with eight wires can carry only 8-bit data words, and hence defines the device as an 8-bit device. A bus normally has a single word memory circuit called a LATCH attached to either end, which briefly stores the word being transmitted and ensures that each bit has settled to its intended state before its value is transmitted.

The bus helps the various parts of the PC communicate. If there was no bus, you would have an unwieldy number of wires connecting every part to every other part. It would be like having separate wiring for every light bulb and socket in your house. There are a variety of buses found inside the computer. The data bus allows data to travel back and forth between the microprocessor (CPU) and memory (RAM). The address bus carries information about the location of data in memory. The control bus carries the control signals that make sure everything is flowing smoothly from place to place. If your computer has expansion slots, there's an expansion bus.Messages and information pass between your computer and the add-in boards you plug in over the expansion bus. Although this is a bit confusing, these different buses are sometimes together called simply "the bus." A user can think of the computer's "bus" as one unit made up of three parts: data, address, and control, even though the three electrical pathways do not run along each other (and therefore don't really form a single "unit") within the computer.

There are different sizes, or widths of data buses found in computers today. A data bus' width is measured by the number of bits that can travel on it at once. The speed at which its bus can transmit words, that is, its bus BANDWIDTH, crucially determines the speed of any digital device. One way to make a bus faster is to increase its width; for example a 16-bit bus can transmit two 8-bit words at once, 'side-by-side', and so carries 8-bit data twice as fast as an 8-bit bus can. A computer's CPU will typically contain several buses, often of differing widths, that connect its various subunits. It is common for modern CPUs to use on-chip buses that are wider than the bus they use to communicate with external devices such as memory, and the speed difference between on- and off-chip operations must then be bridged by keeping a reservoir of temporary data in a CACHE. For example many of the Pentium class of processors use 256 bits for their fastest on-chip buses, but only 64 bits for external links.

An 8-bit bus carries data along 8 parallel lines. A 16-bit bus, also called ISA (Industry Standard Architecture), carries data along 16 lines. A 32-bit bus, classified as EISA (Enhanced Industry Standard Architecture) or MCA (Micro Channel Architecture), can carry data along 32 lines.

The speed at which buses conduct signals is measured in megahertz (Mhz). Typical PCs today run at speeds between 20 and 65Mhz. Also see CPU, Expansion Card, Memory, Motherboard, RAM, ROM, and System Unit.

How Does It Work?

A bus transfers electrical signals from one place to another. An actual bus appears as an endless amount of etched copper circuits on the motherboard's surface. The bus is connected to the CPU through the Bus Interface Unit.

Data travels between the CPU and memory along the data bus. The location (address) of that data is carried along the address bus. A clock signal which keeps everything in synch travels along the control bus.

The clock acts like a traffic light for all the PC's components; the "green light" goes on with each clock tick. A PC's clock can "tick" anywhere from 20 to 65 million times per second, which makes it seem like a computer is really fast. But since each task (such as saving a file) is made up of several programmed instructions, and each of those instructions takes several clock cycles to carry out, a person sometimes has to sit and wait for the computer to catch up.

Arithmetic Logic Unit (ALU)

What is Arithmetic Logic Unit (ALU)?

Arithmetic Logic Unit (ALU): A subunit within a computer's CENTRAL PROCESSING UNIT that performs mathematical operations such as addition, and logical shifts on the values held in the processors REGISTERS or its ACCUMULATOR.  

It is the size of the word that the ALU can handle which, more than any other measure, determines the word-size of a processor: that is, a 3Z-bit processor is one with a 32-bit ALU.

The simplest sort of ALU performs only addition, BOOLEAN LOGIC (including the NOT or complement operation) and shifts a word one bit to the right or left, all other arithmetic operations being synthesized from sequences of these primitive operations. For example, subtraction is performed as complement-add, multiplication by a power of two by shifting, division by repeated subtraction. However, there is an increasing tendency in modern processors to implement extra arithmetic functions in hardware, such as dedicated multiplier or divider units.

The ALU might once have been considered the very core of the computer in the sense that it alone actually performed calculations. However, in modern SUPERSCALAR processor architectures this is no longer true, as there are typically several different ALUs in each of several separate integer and floating-point units. An ALU may be required to perform not only those calculations required by a user program but also many internal calculations required by the processor itself, for example to derive addresses for instructions that employ different ADDRESSING MODES, say by adding an offset to a base address. Once again, however, in modern architectures there is a tendency to distribute this work into a separate load/store unit.

The three fundamental attributes of an ALU are its operands and results, functional organization, and algorithms.

Operands and Results

The operands and results of the ALU are machine words of two kinds: arithmetic words, which represent numerical values in digital form, and logic words, which represent arbitrary sets of digitally encoded symbols. Arithmetic words consist of digit vectors (strings of digits).

Functional Organization of an ALU

A typical ALU consists of three types of functional parts: storage registers, operations logic, and sequencing logic.

32Bit

What is 32-Bit?

The word "bit" attached to a number can refer to several things, depending on the context. The term 32-bit is often applied to the following:

1. 32-bit refer how much information stored in the "registers" of the computer's central processing unit, which is an indication of speed and performance.

2. 32-bit refer the size of data bus through which the processor sends out the information. 32-bit bus can address 4,294,967,296 words (232), which would correspond to 4 gigabytes. The larger data bus enables faster transfer of data to and from storage. Most personal computers today use a 32-bit bus,

3. It can refer to how much information in memory a computer can use.

4. It can refer to the depth of the pixels on the monitor, which creates the color and the resolution of the images, 32-bit Color (so-called TRUE COLOUR).

5. It can refer to the program that uses the 32-bit internal registers and large memory capacity.

6. It can refer to the Operating System; Windows 2000 are true 32-bit operating systems,

7. It can refer to FAT file system, FAT32 allows each disk to be divided into a larger number of clusters (allocation units);

8. It can refer to binary address.

9. It can refer to 32-bit chip.

A bit is a tiny electronic signal. In any context, the bigger the bit number, the more powerful, faster, or more colorful the feature.

Boot

What is Boot? How does it Work?

To boot or boot up means to start your computer system, usually by turning on the power and/or pushing the "on" button. It's called "booting" because the computer is going inside itself and turning itself on (doing a lot of preliminary checking and adjusting before it's ready to run your programs). Hence the machine is considered to be "pulling itself up by its own bootstraps."

 When the computer is first turned on or restarted, it reads the startup instructions found in the ROM BIOS chips. These instructions tell the computer to check the system over (a series of tests called the POST). Certain information (such as the amount of memory and the number and type of disk drives) about the PC is stored in a special chip called CMOS, and that information is also verified during boot. The last thing that happens during boot is the loading of the operating system, which is found on the hard disk drive or on a floppy disk in drive A. The computer cannot do anything without first loading an operating system into memory, because it's the operating system that manages all of the computer's basic functions.

Information in the operating system files continues the booting process. During a PC boot, the CONFIG.SYS file is located, and its instructions are executed. The CONFIG.SYS is a special file that fine-tunes the PC, customizing it so it can access optional peripherals (such as the mouse or the modem) and unused areas in memory. Next, the AUTO EXECBAT file is located, and its instructions are executed. The AUTOEXEC BAT file contains commands (such as those to start a particular program or change the prompt) that the user wants run at boot. Once the startup files have been found and executed, the computer is fully booted and ready to go.

How Does it Work

DOS is made up of three parts: IO.SYS, MSDOS.SYS, and COMMAND.COM. IO.SYS works with ROM BIOS to control the computer's input/output functions; MSDOS.SYS(sometimes called the kernel) manages files, runs programs, and performs basic system functions; COMMAND. COM performs all the DOS commands. In addition,

COMMAND.COM functions as the overall "manager" for the computer. During the boot process, the three parts of the operating system are loaded into memory one at a time. After IO.SYS is loaded, it checks to see if all the system components are responding properly. MSDOS.SYS is loaded next so it can perform the commands in the CONFIG.SYS (a special configuration file). COMMAND.COM is loaded last and is kept in memory so that DOS commands (such as COPY) can be executed when needed. COMMAND.COM then executes the commands in AUTOEXEC.BAT, which completes the boot process.

Control Unit

What is control unit?

A control unit (or controller, same thing) is a piece of hardware that manages the activities of peripherals (separate devices attached to the computer, such as monitors, hard drives, printers, etc.) Control units found on personal computers are usually contained on a single printed circuit board. The control unit acts as a sort of "go-between," executing transfers of information between the computer's memory and the peripheral. Although the CPU (central processing unit-the "big boss" in the computer) gives instructions to the controller, it is the control unit itself that performs the actual physical transfer of data.

The control unit fetches one or more new instructions from memory (or an INSTRUCTION CACHE), DECODES them and dispatches them to the appropriate FUNCTION UNITS to be executed. The control unit is also responsible for setting the LATCHES in various data paths that ensure that the instructions are performed on the correct operand values stored in the REGISTERS.

In a CISC processor the control unit is a small processor in its own right that executes MICROCODE programs stored in a region of ROM that prescribe the correct sequence of latches and data transfers for each type of macro instruction. A RISC processor does away with microcode and most of the complexity in the control unit, which is left with little more to do than decode the instructions and turn on the appropriate function units.

32-bit computer

What is 32-bit computer?

The term 32-bit computer (or 8-bit or 16-bit) refers to the power of the central processing unit (CPU), which is the chip that runs the computer. A CPU that can process 8 bits of information at a time (the minimum configuration for a computer) is called an 8-bit computer. If the CPU can process 16 bits at a time, it is a 16-bit computer, and the same for 32-bit.

But you know what? Even though the CPU can internally process 16 or 32 bits at a time, it doesn't mean the rest of the computer can use that big of a chunk of information. After the data gets processed, it has to get on a bus and be sent to the rest of the computer. Many computers with 16-bit processors (cpus) have an external data bus that is only 8 bits wide, so essentially it doesn't matter whether the CPU is 16 bits or not-only 8 bits can get used at a time anyway. (Yes, you can think of the bus as a little thing with wheels that carts information around to where it needs to go.) The same is true for computers advertised as 32-bit machines; on some computers the external data bus is only 16 bits wide. Nowadays most computers are made with data buses to match the processor.

analogue

What is analogue or analog Computer?

The word analog is derived from the Greek ana-logon, meaning "according to a ratio." A computer that represents numbers by some continuously variable physical quantity, whose variations mimic the properties of some system being modeled. Analogue computers have been built using mechanical motion (such as rotation), pneumatic or hydraulic pressure, or electrical voltage as the requisite quantity.

For example, an old fashioned carburetor may be considered a simple analogue computer that computes a petrol/air mixture strength function given the inputs of throttle pedal position and engine airflow.

The military has used analogue computers for artillery range finding, and they are used to simulate car suspensions and similar elastic systems where real-time performance is valuable. However, in common with other analogue circuits, they lack digital logic's robustness against errors introduced by stray fluctuations.

In an electronic analog computer, the output voltage of an operational amplifier varies in response to its input signals analogously to how a variable in the physical system being modeled responds to its conditions.

BIOS

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.

HybridComputers

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.

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 micro computers, 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 super computer.

ENIAC

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).

Supercomputer

What is Supercomputer?

Super computers 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.

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 ofkilobytes, 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.

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. 

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.

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. Mini computers 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.

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 mousedriver, 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.

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. 

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.

File Format

What is 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 Word Perfect 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.