Physics First Paper by Jafor Iqbal.pdf

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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SSC Physics Creative question with answer.pdf

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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Professors BCS Bangla Book.pdf

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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Physics Second Paper book.pdf

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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Chemistry Second Paper book. pdf

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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