HSC ICT APK

 

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 (a) What is a Nuclear Family?
(b) How many types of family we can find?
(c) Why this type of family is getting popular today?

Database            Programming            HTML               Numbure System

(d) What are the advantages of a nuclear family?
(e) Is there any disadvantage of a nuclear family?
(f) What type of family do you like most and why?
(g) How is Nuclear family different from extended family?

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20. Nuclear Family

(a) What is a Nuclear Family?
(b) How many types of family we can find?
(c) Why this type of family is getting popular today?
(d) What are the advantages of a nuclear family?
(e) Is there any disadvantage of a nuclear family?
(f) What type of family do you like most and why?
(g) How is Nuclear family different from extended family?

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A nuclear family is a small one containing father, mother and their children. There are two types of families we can in our society, one is nuclear family and the other is extended family. In a nuclear family only parents and children live, but in an extended family there might be grandparents, grand children, uncle and aunts live together. Life is becoming more expensive day by day. That’s why nuclear family is preferred. This type of family gives any one the opportunity to concentrate on his own activities. An extended family consists of many members. All members in this family deserve attention. But they can’t concentrate on their own activities. Personal freedom and privacy are hampered in an extended family. It is true that a nuclear family is boring and tiresome to some extent. The members seldom get anyone to share their feelings, joy or sorrows. But these drawbacks can be overcome if the members spend their leisure in a productive way. They can also do some social works or engage themselves in cultural or any educative activities. They can also visit their relatives to avoid their monotony. Despite some disadvantages I like nuclear family, because I think to cope with the modern world. We have to prepare ourselves in an organized way. And it is possible only by staying in a calm and cool family environment. A nuclear family can give us an effective and proper opportunity to do something with full concentration. Money is also a factor. In a nuclear family its members are limited, so we can easily fulfill our demand within our limited income. So considering all these positive sides we should make a consciousness among ourselves to make our family small.

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You Can Win in Bangla.pdf

12. A Trade Fair 

(a) What do you mean by a trade fair?
(b) Why is a trade fair organized?
(c) In Bangladesh where is a trade fair normally arranged?
(d) How is the fair arranged? (e) What things are found in a trade fair?

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A trade fair is a fair for the display of industrial goods to the foreign buyers to get them acquainted with the exportable items of the country. By arranging trade fair we can make people aware of the market price. We can inform the customers about the quality of the product. In a trade fair a lot of companies take active part. In our country every year we arrange a lot of trade fairs. The government organizes an international trade fair every year in Sher-e-Bangla Nagar. A trade fair gives immense pleasure and opportunity to the customers. So it cannot be organized by an individual. It is normally held once a year. A great publicity is done for this purpose. And this publicity is made through advertisement in the national and international dailies to draw the attention of the industrialists and producers. The host country also advises friendly countries to install stalls in trade fair to display their exportable goods to the importers of the host country. As a trade fair gives scope to a country to display her products, friendly countries gladly respond to the call of the host countries. There are also arrangements for recreation, food etc, for the visitors. Thus a trade fair is very much useful. A host country can know the other parts of the globe through a trade fair. A trade fair should be held every year to encourage importers of foreign countries to import goods from our country. The day is no more so far when we shall be able to import necessary goods keeping the balance of trade in our favour.

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Input/Output Methods 

There are three basic methods by which data can be read (or input) from or written (or output) to a peripheral device and RAM. These methods are referred to as: programmed I/O, interrupt I/O, and direct memory access. In programmed I/O, the MPU directly controls all data transfers and other I/O operations. 

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This is accomplished with input or output instructions. When an input operation is desired, the MPU issues an input command and awaits the arrival of the data at the bus. From the bus the data are moved to memory. Similarly for an output operation, the MPU transmits the data to the bus and issues a command to the output device through the appropriate interface. Once data transfer is initiated, the MPU should wait for its completion and the bus to be freed before beginning a new transfer. This method is commonly used in personal computers. In the interrupt I/O method, the MPU does not wait for the input/output devices to complete their tasks. The control of the operation is given to a channel. The channel signals the MPU when the operation has been completed. This is accomplished by means of an interrupt. Upon completion of the execution of the current instruction, the MPU may then initiate another I/O operation. Direct memory address method is the fastest of the three methods. It requires a multibus architecture and allows the MPU to be bypassed completely. A direct memory access controller is connected between RAM and an input or output device. This method is the most expensive of the all and therefore is not used except with very high-speed input/output devices. 

Telecommunications Between Microcomputers 

Most microcomputers also support the transfer of data through telephone line. This is facilitated by means of an add-on device known as a modem. In telecommunications, one computer or terminal issues a command, or some form of output. This digital output from the computer, is modulated, or converted to an analog signal, by a modem interfaced to the sending computer. The signal is then carried over the telephone line and received at another modem some distance away. This second modem then demodulates, or converts the analog signal back to a computer-compatible digital signal. The name modem performs the functions of modulation and demodulation. Thus, with the aid of a modem and a serial interface to a microcomputer, communication can take place over long distances. The speed with which these communications take place is dependent on the modem employed.

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English For Today For Class Eleven. pdf

Lesson 1: Microcomputer and Organization 

1.1 Learning Objectives 
On completion of this lesson you will be able to:
• understand structure of a microcomputer
• understand communication techniques between processor and other devices
• understand telecommunications for distant microcomputer.

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1.2 Architecture of a Microcomputer 

The most modern microcomputers utilize a motherboard, a single large circuit board containing the microprocessor unit (MPU), ROM, RAM, and other associated circuits. These elements are linked through a series of parallel metal lines etched into the motherboard called the system bus. The system bus carries three types of information; these are: control, address, and data. Control information is carried by a number of control lines, addresses by a number of address lines and data by data lines. The width of the bus is important to the performance of the computer. The wider the bus, the more information can be carried at one time and the greater the throughput of the system. Most 16-bit microcomputers use 8 or 16-bit buses, 32-bit microcomputers use 8-bit, 16-bit, and 32-bit buses, while 64-bit microcomputers use 16-bit, 32-bit and 64-bit buses. A number of slots provide access to the system bus (Figure 3.1). Input/output devices can be connected to the microcomputer through the slots and appropriate interface circuit boards. The slots can also be used to expand the RAM capability of the microcomputer.

I/O Interface

Communications between an input/output device and the MPU take place through an interface. The interface converts the data from a form used by one of these devices to a form acceptable by the other. It must also adjust for speed differences between the processor and the other device. The interface circuits of microcomputers correspond to the I/O control units used on larger computer systems.

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HSC Biology Book.pdf

3.3 Computer Generations 

Developments over the years have resulted in machines with greatly increased speeds, storage or memory, and computing power. These developments were so far-reaching and numerous that they are generally categorized by generations. Each generation is initiated by significant advances in computer hardware or computer software that run the machines. 

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First Generation (1942-1959) 

First-generation computers utilized vacuum tubes in their circuitry and for the storage of data and instructions. The vacuum tube was bulky, caused tremendous heat problems, and was never a completely reliable device, it caused a great number of breakdowns and inefficient operations. Magnetic cores began to replace the vacuum tube as the principal memory device in the early machines. Small doughnut-shaped cores were strung on wires within the computer. Programs were written in machine language employing combinations of binary digits 0 and 1. 

Second Generation (1959-1965) 

The second generation of computers saw the replacement of the vacuum tubes with the transistors. A transistor can be thought of as a switch, but with no moving parts. Because of the high speed operation and its small size, computers were developed that were able to perform a single operation in microseconds and were capable of storing tens of thousands of characters. Manufacturers began producing business-oriented computers with more efficient storage and faster input and output capabilities. Second generation computers were reliable, compact in size, and virtually free of heat problems. Programming was done in both machine and symbolic language. Symbolic language utilized symbolic names of representations for computer commands and allowed the use of symbolic names for items of data. This language is also known as assembly language. 

Third Generation (1965-1970) 

These computers were characterized by integrated circuits with components so small that in many cases they were hardly visible to the naked eye. Third generation computers were characterized by increased input/output, storage, and processing capabilities. Input/output devices could communicate with computers over great distances via ordinary telephone lines or special communication lines, could scan a page and input the “observed” information directly into the computer, could display pictures on a television-like screen, could make musical sounds, and could even accept limited voice input. Storage capabilities were increased and millions of characters could be stored and randomly accessed in fractions of a second. Third-generation computers could process instructions in nanoseconds. In addition, computers were able to process several programs or sets of instructions simultaneously. Programmers were able to make use of high-level problem oriented and procedure oriented languages that closely resemble the commonly used form of expressions. 

Fourth Generation (1970 - ) 

The fourth generation computers pass still greater input, output storage, and processing capabilities. In the fourth generation of computers monolithic storage devices were introduced. In the early 1970s IBM introduced the concept of virtual storage into their 5000 and 370 series of computers. Machines previously limited to a maximum internal storage capability of approximately 1 million characters now possessed a virtual storage capability in billions and trillions of characters. With this capability a machine could execute a program many times the size of the machine’s actual memory capacity. Now a days, the compact disk (CD) promises to become the data storage medium of choice. A compact disk read-only memory (CD ROM) is encoded with on and off bits. Bits are stored on the disk’s (3.5-inch dia) aluminum surface as tiny pits at varying depths. The average CD can store about 4,800 million bits or 600 million characters of data. This is approximately a quarter of a million pages of text. The most impressive advancement has occurred with respect to software. As a result of these changes, access to substantial computer power, previously only affordable by very large business concerns, is now economically feasible for the small business and personal applications.

Fifth Generation 

Fifth generation of computers is on the horizon. They will be unlike any computer existing today. They will be capable of reasoning, learning, making inferences and otherwise behaving in ways usually considered exclusive of humans. These computers will be equipped with massive primary-storage capabilities and extremely fast processing speeds. Software will proliferate and get much bigger and much cheaper. Hardware will continue to shrink in size but internal memory will increase dramatically. “Talking machines” will be common place. Voice-recognition, the ability for a machine to understand and obey spoken words, will also advance. Industrial and personal robots will roll and walk into our lives. Expert systems software will place the knowledge of experts and consultants (such as doctors, lawyers, teachers) at our disposal. Huge computers will be linked in parallel offering computing power of an inconceivable magnitude.

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HSC Biology.pdf

Lesson 3: History and Generations of Computers 

3.1 Learning Objectives 
On completion of this lesson you will be able to :
• trace the history of computers
• follow the computer generations.

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3.2 The Beginning 

Different devices and tools have been employed in calculation and processing of data. An ancient calculating device is the abacus, a mechanical calculating device first used around 2500 B.C. to add and subtract. Scientists and mathematicians later sought other means to aid their endeavors. John Napier, a Scottish mathematician, developed (about 1610) a series of rods made of bones (commonly called Napier's bones) that could be arranged to produce the products of selected numbers. He used these rods to produce the first table of logarithms. In 1865 the French mathematician Blasé Pascal improved on this concept and produced a mechanical calculator called Pascaline. It was more compact and easier to use than Napier's bones. The Pascaline was capable of performing addition and subtraction. All attempts to produce a calculator capable of performing all the four arithmetic operations and producing mathematical tables quickly and accurately were not successful until 1820. Thomas de Colmar of France produced the arithmometer, the first four-function practical mechanical calculator. A young English mathematician named Charles Babbage, of Cambridge University contributed substantially towards the development of computers. Babbage gave much thought to the design of a device to produce mathematical and navigational tables and came upon a principle that used the “differences” between previous values in a table to produce new values. Babbage was able to construct a working model to illustrate the principle of the difference engine. Babbage started work on a steamdriven version of the difference engine capable of calculating and printing results at a rate of two twenty-digit numbers per minute. Babbage built part of the machine but abandoned it in favor of a more powerful and versatile machine, the analytical engine. The analytical engine was designed to use punched cards to provide a constant flow of information through the machine's elaborate series of columns, gears, wheels, and levers. The analytical engine included all the functional units of modern computers: input of data, arithmetic unit for computation, memory for data and instructions, and display for output. This was an ambitious project during a time when electronics,transistors, and chips did not exist. The engine was a puzzle to all but a few mathematicians. This machine, however, was never built. Nearly a century later a new generation of scientists and engineers equipped with new developments brought Babbage's vision back into focus for future advancements in computer technology. Insignificant progress took place over the next decades. In the United States the 1890 census was approaching, and there was no foreseeable way that it could be completed by 1900, as required by the constitution. Herman Hollerith, an employee of the Census Office in Washington, started to develop an automated device to complete this task in the allotted ten years. The result was Hollerith's tabulator. A manual card puncher, a card reader, and an electromechanical card sorter were the main components of the census tabulator. With this tabulator, Hollerith was able to complete the census count in only two years. Hollerith's success paved the way for further research and development. Analog computers, a new class of computing devices, emerged. These devices used electrical voltages to represent physical quantities. They functioned by establishing an analogy between a physical quantity and a voltage level. They were very fast but not sufficiently exact, or dependable. The first electronic computers, the ABC (Atanasoff Berry Computer) and the ENIAC (Electronic Numerator, Integrator, Analyzer, and Computer) were built in the early 1940s. The ABC, built by Atanasoff and Berry, was the first, electronic computer using vacuum tubes. The ENIAC, built by Eckert and Mauchly, was an extensively used specialpurpose computer. In 1949, at Cambridge, the first general-purpose electronic computer operating under the control of a stored program, the EDSAC (Electronic Delay Storage Automatic Computer), was completed. A stored program is a set of instructions stored in memory that guides the computer, step by step, through a process. John Von Neumann, an originator of the stored-program concept, developed the IAS (Institute for Advanced Study) computer at Princeton University. This machine was the realization of John Von Neumann, ideas on computer design. Most computers built after the IAS computers have “Von Neumann” characteristics. A group of MIT scientists headed by Ken Olsen developed the Whirlwind computer, more than twenty times faster than the ENIAC. Both the IAS and Whirlwind computers introduced computational innovations of astronomical proportions.

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Mainframe Computers

Larger computers generally consist of modules mounted on a chassis or mainframe and are known as mainframe computers. They vary in size, from those slightly larger than a minicomputer to supercomputers (like the Cray and Control Data Cyber computers). 

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Mainframe computer systems offer substantial advantages over mini-computers or microcomputers. Some of these are; greater processing speed, greater storage capacity, a larger variety of input/output devices, support for a number of high-speed secondary storage devices, multiprogramming, and time sharing. Owing to tremendous expense in operating a mainframe computer, this computer system must be operated efficiently. Operating a mainframe at the required level of efficiency requires a very large and highly trained staff. Mainframe Computer systems are generally used by large businesses, universities, governmental agencies, and the military. These systems are often coupled with other computer systems in a large network to provide enormous computing power. This is what is referred to as a distributed data processing system. 

Supercomputers The large and powerful mainframe computer is called a supercomputer. The astronomical cost of the super-computers has limited their development to only a few hundred worldwide. The Cray X-MP, Cray XTS-HE is an example of a supercomputer. Such supercomputers are applied to the solution of very complex and sophisticated scientific problems and for national security purposes of some advanced nations. Smaller, less costly minisupercomputers have been developed by several manufacturers. These computers provide approximately half the power of the supercomputer but at a fraction of the cost. The relative low cost has made the minisupercomputer an attractive to buy for mid-sized to large applications. Many Wall Street brokerage firms in the United States use computers to speed up the processing of large financial models to keep track of securities that have tendencies to fluctuate greatly.

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Microcomputers 

Microcomputers are microprocessor based small laptop or desktop systems with varying capability depending on the input/output and secondary storage devices supporting it. The brain of a microcomputer is the microprocessor, a silicon chip containing the necessary circuits to perform arithmetic/logic operations and to control input/output operations. 

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A microprocessor is an integrated circuit consisting of thousands of transistors squeezed onto a tiny chip of silicon. The chip is packaged as a single integrated circuit. A microcomputer system is formed by adding an input/output capability and a memory to the microprocessor. Early microcomputers had a limited processing potential and limited choice of input/output devices. Present day microcomputers have wider processing capabilities and support a wide range of input/output devices. Today microcomputers are available with a selection of input/output devices varying from a cassette recorder to a voice synthesizer. In addition to general-purpose computations, microcomputers are used for special purpose applications in automobiles, airplanes, toys, clocks, appliances etc. High-end supermicros are known as workstations. The workstation represents the bridge between the microcomputers and minicomputers. It is a microcomputer with many of the capabilities of larger minicomputers but costing much less. Initially designed for use by engineers and designers, and today they are popular for general uses. These workstations can run more than one application for a user. This is known as multitasking. A workstation is also a multi-user system that can be shared by several users at the same time.

Minicomputers

A Minicomputer system performs the basic arithmetic and logic functions and supports some of the programming languages used with large computer systems. They are physically smaller, less expensive, and have a small storage capacity than mainframes. Minicomputers are ideally suited for processing tasks that do not require access to huge volumes of stored data . As a result of their low cost, ease of operation, and versatility, minicomputers have gained rapid acceptance from their introduction in the mid-sixties. Some of the larger and expensive minicomputers are capable of supporting a number of terminals in a time-shared mode.

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2.4 Analog and Digital Computers 

Two types of computers currently available. These are analog and digital computers. Earlier discussion was only on digital computers. An analog computer represents quantities by physical analogies. It represents physical quantities, such as distance, velocity, acceleration, temperature, pressure, or angular position, forces or voltages in mechanically or electrically equivalent circuits. That is, it functions by setting up physical models corresponding to mathematical functions. 

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An automobile speedometer is an example of an analog computing device. It converts the rotational rate of the drive shaft of an automobile into the numerical value of the speed of the vehicle. Similarly, a thermometer functions as an analog device by converting the movement of a column of mercury into a temperature reading. Data inputs to an analog computer results from a measuring processes. These computers are ideal in situations where data can be accepted directly from measuring instruments. The ability to collect data at high speeds and to process data at equally high speeds, makes analog computers uniquely suited to controlling processes of oil refineries, steel mills, weapon systems and similar operations. An analog computer does not require any storage capability as it measures and compares quantities in a single operation. The output from an analog computer is generally in the form of readings on a dial (as in the speedometer and odometer of a car) or a graph on the screen of a cathode ray tube. Analog computers were in use before the invention of the digital computers. There are far more digital computers in use today than analog computers. For the remainder of this book concentration will be on digital computers. 

2.5 Capacity 

The capacity of a computer refers to the volume of data that a computer system can process. Previously a computer's size was an indication of its capacity - the larger the physical size of the computer, the larger its capacity. However, with the current state of micro-miniaturization, measurement is based on the size of a computer by its throughput. Throughput is the amount of processing that can be performed in a given amount of time. Based on throughput, computer systems can be divided into three categories: microcomputers, minicomputers, and mainframe computers, with costs increasing proportional to size.

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English For Today pdf

Lesson 2 : Types of Computers 

2.1 Learning Objectives
On completion of this lesson you will be able to
• classify computers based on purposes
• classify computers based on types
• classify computers based on capacity.

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2.2 Outline 

The computer systems are available in various sizes and with a variety of peripheral or support devices to cover just about every processing need. Because of the variety of computer power and functions available, computers are classified on the basis of purpose, type, and capacity. 

2.3 Purpose 

There are either special-purpose or general-purpose computers. Specialpurpose computers are designed for a specific application or type of application. They are also known as dedicated computers. Many such computers have instructions permanently programmed into them that are designed to perform only one major function. Special-purpose computers are used, to control traffic lights, to control the collection of tolls on certain highways, and in automobiles, weapons, appliances and games etc. 

General-purpose computers are used to handle a variety of tasks. This is possible by the stored-program concept. By this concept, a program containing a series of instructions is prepared for each application and input to and temporarily stored in the computer. Once stored in the computer's memory, this program can be executed, causing the computer to perform the specific function. After the completion of the execution of this program, another program can be input to the computer and the cycle repeated. That is, the same combination of hardware can be used to execute many different programs. 

General-purpose computers have the advantage of versatility over special-purpose computers. But typically general purpose computers are less efficient and slower than special-purpose computers when applied to the same task.

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Humanware 

Humanware refers to the persons who design, program, and operate a computer installation. There are numerous categories of jobs, but the three principal positions required in a large computer installation are system analyst, programmer, and computer operator. 

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People in each of these areas generally perform special-purpose tasks under the supervision of a director or manager. The position of a systems analyst requires the broad background and extensive understanding of the above three job categories. The main task of the system analyst is to study information and processing requirements. A systems analyst defines the applications problem, determines systems specifications, recommends hardware and software changes, and designs information processing procedures. A programmer requires a comprehensive knowledge of one or more programming languages and standard coding procedures. This position does not require the broader understanding of the structure and inner workings of an application. A programmer's principal job is to code or prepare programs based on the specifications made by the systems analyst.

A computer operator requires the least extensive background of the three categories. A computer operator generally performs a series of well defined tasks that will keep the computer operating at maximum efficiency. The operational efficiency of a computer installation is dependent on the quality and abilities of the operational staff.

Procedures

Operations of a data processing center require an extensive and clearly defined set of procedures for performing the essential functions of the installation. These functions generally include obtaining, preparing, and entering data into the computer, processing jobs, initiating new programs and changing or deleting old ones etc. Such procedures must have provision for actions to be taken in the event of hardware or software malfunctions.

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1.3 Components of a Computer System 

A computer is used to process data and a data processing system must consist of more than just machines. A computer system must contain: hardware, software, humanware and operational procedures. 

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Hardware 
Hardware generally refers to the machine or physical equipment t hat performs the basic functions of the data processing cycle. In addition to the computer itself, other hardware devices are also required. These devices may be off-line that is detached from the computer and operating independently or they may be on-line that is directly connected to and controlled by the computer. A printer is an off-line device and a keyboard is an on-line device.

Software 

A program is a sequence of instructions which directs a computer to perform certain functions. A computer must have access to prewritten, stored programs to input and store data, make decisions, arithmetically manipulate and output data in the correct sequence. Programs are referred to as software. Computer system must be supported by extensive software systems. Software is generally categorized as either system software or application software. System software consists of programs that facilitate the use of computer by a user. These programs are sometimes referred to as utility programs. They perform such standard tasks as organizing and maintaining data files, translating programs written in various languages to a language acceptable to the computer, scheduling jobs through the computer, as well as aiding in other areas of general operations. Of all the systems software supplied by the manufacturer of a computer, the most important one is known as the operating system. Application software consists of programs to perform specific user applications. A computer program giving instructions for the steps involved in preparing results of a public examination is an example of applications software. Application programs are either purchased or written by the computer users for specific applications.

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Computer Sikun

Lesson 1: Introduction and Basic Organization 

1.1 Learning Objectives 
On completion of this lesson you will be able to
i) grasp the introductory concepts of a computer and its working principle
ii) understand the basic elements of a computer system.

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1.2 What is a Computer? 

A computer is an electronic machine that stores, retrieves, and manipulates or processes data. It cannot think or reason; it can only carry out instructions given to it. A set of instructions that directs its actions is called a program. Different programs are used to solve different problems. Ability to accept, store, and execute various sets of instructions (or programs) makes the computer the invaluable, allpurpose business tool. The first step of solving a problem by a computer is to develop a suitable computer program and then store in its memory. The computer then carries out the instructions in the program. The instructions of a program generally direct the computer to perform three basic functions over and over again; these functions are input, processing, and output. Collectively, these functions constitute the data processing cycle. 

Input: input devices are connected to feed the computer facts or data to be processed.

Processing: the control and storing of data, numerical comparisons, and arithmetic operations are performed on the input data to produce the desired results.

Output: the computer feeds the processed data or information, to the output devices.

i) The computer reads a program and stores it in the memory. The computer executes program instructions to:

ii) Input data from the disk, the keyboard, or other storage media,

iii) process the data and

iv) Output results to the display screen, disk or other media.

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MP3 Easy Computer.pdf (Free Download)

Lesson 5 : Installing Floppy Disk Drive 

5.1. Learning Objectives 
On completion of this lesson you will be able to describe:
 How to install floppy disk drives.

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5.2. Introduction 

Different types of floppy drives are available today. Installation method of different types of floppies (3 ½, 5 ¼ etc.) in different types of computers (AT, PS/2, clone etc.) are slightly different. Of them installing method of a 3 ½ drive in a modern clone is discussed here. It is discussed here because it is the most popular type of computer in our country. Other types of installations are nearly similar. The steps to install a 3 ½ inch floppy disk drive as drive ‘A:’ are as follows: 

 Place the drive in PC chassis 

 Connect the cables 

 Configure CMOS. 

5.3. Place the Drive in PC Chassis 

The steps to place a 3 ½ inch floppy disk drive are as follows:  Open the computer casing. 

 Insert the floppy disk drive in the 3 ½ inch wide drive bay of the chassis. 

 Insert the screws in the screw holes on both the sides of the drive. 

5.4. Connecting the Cables 

Two cables are connected with a floppy disk drive power and data. Power cable is a 4-wire cable. It comes out from the power supply unit. It is connected with the power cable-connecting slot of the floppy disk drive. It is not possible to connect the power cable in opposite direction. Data cable is a 34-wire cable with 3 connectors and a twist at one end. The opposite end of the twist is connected with the floppy disk controller (or the motherboard, because nowadays the floppy disk controller is built in the motherboard). If we have two floppy drives then one should be drive ‘A:’ and the other should be drive ‘B:’. The drive, which we want to use as drive ‘A:’, is connected with the twisted end of the cable. Now only one connection point on the cable is left. It is the middle connection point. If we have another drive it is connected with the middle (non-twisted) connection point of the cable to use this drive as drive ‘B:’.

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MP3 Daily Science. pdf

Lesson 1 : Types of Parallel Processing 

1.1. Learning Objectives

On completion of this lesson you will be able to : 

i) classify different types of parallel processing techniques. 

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Traditionally, the computer has been viewed as a sequential machine. Most computer programming languages require the programmer to specify algorithms as sequences of instructions. CPUs execute programs by executing machine instructions in a sequence and one at a time. Each instruction is executed in a sequence of operation (fetch instruction, fetch operands, perform operation, store results). This view of the computer has never been entirely true. At the microoperation level, multiple control signals are generated at the same time. Instruction pipelining, at least to the extent of overlapping fetch and execute operations, has been around for a long time. Both of these are examples of performing functions in parallel. When a computer application requires a very large amount of computation that must be completed in a reasonable amount of time, it becomes necessary to use machines with correspondingly large computing capacity. Such machines are called supercomputers. Typical applications that require supercomputers include weather forecasting; simulation of large, complex, physical systems; and computer-aided design (CAD) using high-resolution graphics. As a general quantitative measure, a supercomputer should have the capability to execute at least 100 million instructions per second. In the development of powerful computers, two basic approaches can be followed. The first possibility is to build the system around a highperformance single processor, and to use the fastest circuit technology available. Architectural features such as multiple functional units for arithmetic operations, pipelining, large caches, and separate buses for instructions and data can be used to achieve very high throughput. As the design is based on a single processor, the system is relatively easy to use because conventional software techniques can be applied.

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CPU Speed

There are many components inside the CPU. The CPU clock keeps the working of the components synchronized. By striking each clock a certain amount of work is done. Heart bit in our body is an example of clock tick in computer.

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The unit used for clock speed is megahertz. Hertz means 1 clock tick per second. So ‘Mega’ ‘Hertz’ means 1 million (106) clock tick per second.

Megahertz is the measure of speed of the processor. A microcomputer's speed mostly depends on the processor. So a faster clock means a faster computer.

But this is not hundred percent true. A computer's speed depends on various other things such as memory size, motherboard, bus speed etc.

So increasing only CPU speed by 50% does not make an overall increase of computer’s speed by 50%, it may increase by 20%. Nowadays, the slowest computer you may find will be 25 or 33 MHz 386DX. The fastest speed you’ll hear may get up around 400 MHz Pentium II.

3.4. Word Size

Word size determines how much big a number the computer can operate in one operation. The larger the word size, the bigger the number. Unit of word size is bit. Today most of the processors support 32-bit word size. The largest integer number that a processor with 32-bit word size can manipulate is 232-1. A processor with larger word size is faster than a processor with smaller word size.

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Lesson 1 : Microcomputer

1.1. Learning Objectives

On completion of this lesson you will be able to describe :

i) What is a microcomputer

ii) Different types of microcomputer.

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1.2. Microcomputer

A computer is an electronic machine that stores, retrieves and manipulates or processes data. Microcomputers are microprocessor based small computer. The brain of a microcomputer is the microprocessor, a silicon chip containing the necessary circuits to perform arithmetic and logic operations and to control input-output operations. A microprocessor is an integrated circuit consisting of thousands of transistors squeezed onto a tiny chip of silicon. The chip is packaged as a single integrated circuit. Adding input-output capability and a memory to the microprocessor, a microcomputer system is formed.

Early microcomputers had a limited processing potential and limited choice of input-output devices. Present day microcomputers have wider processing capabilities and support a wide range of input-output devices. In addition to general-purpose computations, microcomputers are used for special purpose applications in automobiles, airplanes, toys, clocks, appliances etc.

High-end super micros are known as workstations. The workstation represents the bridge between the microcomputers and minicomputers. It is a microcomputer with many of the capabilities of larger minicomputers hut costing much less. Initially designed for use by engineers and designers, and today they are popular for general uses. These workstations can run more than one application for a user. This is known as multitasking. A workstation is also a multi-user system that can be shared by several users at the same time.

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3.5. Internal Cache Memory

While working the CPU stores its program and data in the RAM. There are 2 main types of RAM – static and dynamic.
i) Static RAM or SRAM: Faster and 10-20 times more expensive than DRAM.
ii) Dynamic RAM or DRAM: Slower and 10-20 times less expensive than SRAM.

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To save money, the PC uses a lot of DRAM, but it decreases the PC’s speed. To get some speed, small amount of SRAM is used in to the CPU.

This SRAM is called the cache memory. The size of the cache memory is much smaller than the main memory.

The often-used data is stored in this cache memory. Thus the CPU need not access the relatively slow DRAM and the overall speed increases.

There are 2 types of cache memory – internal and external. A PC can have any one or both or none of these two.

i) Internal cache memory: This cache memory is built in to the CPU. It is also called level-1 or L1 cache. Size of the internal cache memory is smaller than the external cache memory.

ii) External cache memory: This cache memory is built on the motherboard. It is also called level-2 or L2 cache.

The Pentium processors normally have 16K internal L1 cache and 256-512K external L2 cache. The Pentium-Pro has all the 2 level cache built in to the processor.

3.6. MMX Technology

For multimedia operations (video, audio etc.) MMX processors can work faster and with improved quality of color and sound. The MMX versions of Intel processors use 57 special purpose instructions. These instructions can work in parallel. These instructions are used to speed up the core algorithms, which are often used for multimedia operations.

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