Internal Memory in Computers: Types, Characteristics, and Data Transfer, Study Guides, Projects, Research of Advanced Computer Architecture

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Advanced Computer Architecture

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Subject: ADVANCED COMPUTER ARCHITECTURE Credits: 4

SYLLABUS

Computer System Generation of computers, Classification of computers, Organization, Structure and function, Von Neumann architecture. System bus, Bus Structure, Elements of Bus design (Type, Arbitration, Timing, Width, Data transfer Type), Interrupts, Instruction Cycle state Diagram with interrupts/Without interrupts, Characteristic of Internal memory (ROM, PROM, EPROM, Flash memory), Input / Output: (External / Peripheral Device, Function of I/O module, Programmer I/O, Interrupt Driver I/O DMA)

The Central Processing Unit ALU, Binary Arithmetic, Floating point Arithmetic, Basic combinational and sequential Circuit Design, RTL representation,

Suggested Reading:

John L. Hennessy and David A. Patterson. Computer Architecture: A Quantitative Approach (Third Edition ed.). Morgan Kaufmann Publishers. Laplante, Phillip A. (2001). Dictionary of Computer Science, Engineering, and Technology.

The first computer like machine was the Mark I developed by a team from IBM and Harvard University. It used mechanical telephone relays to store information and it processed data entered on punch cards. This machine was not a true computer since it could not make decisions.

In June 1943, work began on the world's first electronic computer. It was built at the University of Pennsylvania as a secret military project during World War II and was to be used to calculate the trajectory of artillery shells. It covered 1500 square feet and weighed 30 tons. The project was not completed until 1946 but the effort was not wasted. In one of its first demonstrations, the computer solved a problem in 20 seconds that took a team of mathematicians three days. This machine was a vast improvement over the mechanical calculating machines of the past because it used vacuum tubes instead of relay switches. It contained over 17,000 of these tubes, which were the same type tubes used in radios at that time.

The invention of the transistor made smaller and less expensive computers possible. Although computers shrank in size, they were still huge by today’s standards. Another innovation to computers in the 60’s was storing data on tape instead of punched cards. This gave computers the ability to store and retrieve data quickly and reliably.

Classification of Computers

ƒ Mainframe Computers ƒ Minicomputers ƒ Microcomputers ƒ Supercomputers

Mainframe computers are very large, often filling an entire room. They can store enormous of information, can perform many tasks at the same time, can communicate with many users at the same time, and are very expensive.. The price of a mainframe computer frequently runs into the millions of dollars. Mainframe computers usually have many terminals connected to them. These terminals look like small computers but they are only devices used to send and receive information from the actual computer using wires. Terminals can be located in the same room with the mainframe computer, but they can also be in different rooms, buildings, or cities. Large businesses, government agencies, and universities usually use this type of computer.

Minicomputers : are much smaller than mainframe computers and they are also much less expensive. The cost of these computers can vary from a few thousand dollars to several hundred thousand dollars. They possess most of the features found on mainframe computers, but on a more limited scale. They can still have many terminals, but not as many as the mainframes. They can store a tremendous amount of information, but again usually not as much as the mainframe. Medium and small businesses typically use these computers.

Microcomputers : These computers are usually divided into desktop models and laptop models. They are terribly limited in what they can do when compared to the larger models discussed

above because they can only be used by one person at a time, they are much slower than the larger computers, and they cannot store nearly as much information, but they are excellent when used in small businesses, homes, and school classrooms. These computers are inexpensive and easy to use. They have become an indispensable part of modern life.

Computer Tasks

ƒ Input ƒ Storage ƒ Processing ƒ Output

When a computer is asked to do a job, it handles the task in a very special way.

1. It accepts the information from the user. This is called input.
2. It stored the information until it is ready for use. The computer has memory chips, which are designed to hold information until it is needed.
3. It processes the information. The computer has an electronic brain called the Central Processing Unit, which is responsible for processing all data and instructions given to the computer.
4. It then returns the processed information to the user. This is called output.

Every computer has special parts to do each of the jobs listed above. Whether it is a multi- million dollar mainframe or a thousand dollar personal computer, it has the following four components, Input, Memory, Central Processing, and Output.

The central processing unit is made up of many components, but two of them are worth mentioning at this point. These are the arithmetic and logic unit and the control unit. The control unit controls the electronic flow of information around the computer. The arithmetic and logic unit, ALU, is responsible for mathematical calculations and logical comparisons.

Input Devices

ƒ Keyboard ƒ Mouse ƒ Scanner ƒ Microphone ƒ CD-ROM ƒ Joystick

Byte – The amount of space in memory or on a disk needed to store one character. 8 bits = 1 Byte

Since computers can handle such large numbers of characters at one time, metric prefixes are combined with the word byte to give some common multiples you will encounter in computer literature.

Kilo means 1000 kilobyte (KB) = 1000 Bytes

Mega means 1,000,000 megabyte (MB) = 1,000,000 Bytes

Giga Means 1,000,000,000 gigabyte (GB) = 1,000,000,000 Bytes

At this point it would be good to point out why information stored in RAM is lost if the power goes off. Consider the way the following characters are translated into binary code for use by the computer.

A 01000001

B 01000010

C 01000011

X 01011000

Z 01011010

Consider the column at the right, which represents how the computer stores information. Each of the 1’s in the second column represents a circuit that is “on”. If the power goes off, these circuits can NOT be “on” any more because the electricity has been turned off and any data represented by these circuits is lost

Central Processing Unit (CPU) The central processing unit is one of the two most important components of your microcomputer. It is the electronic brain of your computer. In addition to processing data, it controls the function of all the other components. The most popular microprocessors in IBM compatible computers are made by Intel. The generations of microprocessors are listed below.

1993 Pentium 1996 P- 2002 P-

Output Devices

Monitor Speakers Printer Impact Daisy Wheel Dot Matrix Non-Impact Ink Jet Laser

Storage Devices

Floppy disk Tape drive Local drive (c) Network drive (z) CD-ROM Zip disk

Telecommunications

Telecommunications means that you are communicating over long distances usually using phone lines. This enables you to send data to and receive data from another computer that can be located down the street, in another town, or in another country.

Telecommunications requires a communication device called a modem, which connects your computer to a standard phone jack. A modem converts the digital signals that your computer uses into analog signals that can be transmitted over the phone lines. To use a modem, you must also have communication software to handle the transmission process.

Computer Software

System Software

System software will come provided with each computer and is necessary for the computer’s operation. This software acts as an interpreter between the computer and user. It interprets your instructions into binary code and likewise interprets binary code into language the user can understand. In the past you may have used MS-DOS or Microsoft Disk Operating System which was a command line interface. This form of system software required specific commands to be typed. Windows 95 is a more recent version of system software and is known as a graphical interface. This means that it uses graphics or "icons" to represent various operations. You no longer have to memorize commands; you simply point to an icon and click.

equal to 12^4 +02 3 +12^1 +12 0 =23. A decimal number is converted into an equivalent binary number by dividing the number by 2 and storing the remainder as the least significant bit of the binary number. For example, consider the decimal number 23. Its equivalent binary number is obtained as show below in figure

CONVERSION OF DECIMAL TO BINARY EXAMPLE. 23 = (0111)

Hexadecimal Numbers

High valued binary numbers will be represented by a long sequence of 0's and 1's. A more concise representation is using hexadecimal representation. The base of the hexadecimal system is 16 and the symbols used in this system are 0,1,2,4,5,6,7,8,9,A,B,C,D,E,F. Strings of 4 bits have an equivalent hexadecimal value. For example, 6B is represented by 0110 1011 or 110 1011, 3E1 is represented by 0011 1110 0001 or 11 1110 0001 and 5DBE34 is represented by 101 1101 1011 1110 0011 0100. Decimal fractions can also be converted to binary fractions.

Parity Check Bit

Errors may occur while recording and reading data and when data is transmitted from one unit to another unit in a computer Detection of a single error in the code for a character is possible by introducing an extra bit in its code. This bit, know as the parity check bit , is appended to the code. The user can set the parity bit either as even or odd. the user chooses this bit so that the total number of ones ('1') in the new code is even or odd depending upon the selection. If a single byte is incorrectly read or written or transmitted, then the error can be identified using the parity check bit.

Input Devices

Key Board

The most common input device is the Keyboard. It is used to input letters, numbers, and commands from the user.

Mouse

Mouse is a small device held in hand and pushed along a flat surface. It can move the cursor in any direction. In a mouse a small ball is kept inside and the ball touches the pad through a hole at the bottom of the mouse. When the mouse is moved, the ball rolls. This movement of the ball is converted into electronic signals and sent to the computer. Mouse is very popular in the modern computers that use Windows and other Graphical User Interface (GUI) applications.

Magnetic Ink Character Recognition (MICR)

In this method, human readable characters are printed on documents such In this method, human readable characters are printed on documents such as cheque using special magnetic ink. The cheque can be read using a special input unit, which can recognize magnetic ink characters. This

method eliminates the need to manually enter data from cheques into a floppy. Besides saving time, this method ensures accuracy of data entry and improves security.

Optical Mark Reading and Recognition (OMR)

In this method, special pre-printed forms are designed with boxes which can be marked with a dark pencil or ink. Such a document is read by a document reader, which transcribes the marks into electrical pulses which are transmitted to the computer. These documents are applicable in the areas where responses are one out of a small number of alternatives and the volume of data to be processed is large. For example:

• Objective type answer papers in examinations in which large number of candidates appear.
• Market surveys, population survey etc.,
• Order forms containing a small choice of items.
• Time sheets of factory employees in which start and stop times may be marked.

The advantage of this method is that information is entered at its source and no further transcription is required.

Optical Character Recognition (OCR)

An optical scanner is a device used to read an image, convert it into a set of 0's and 1's and store it in the computer's memory. The image may be hand-written document, a typed or a printed document or a picture.

Bar Coding

In this method, small bars of varying thickness and spacing are printed on packages, books, badges, tags etc., which are read by optical readers and converted to electrical pulses. The patterns of bars are unique an standardized. For example, each grocery product has been given unique 10-digit code and this is represented in bar code form on every container of this product.

Speech Input Unit

A unit, which takes spoken words as its input, and converts them to a form that can be understood by a computer is called a speech input unit. By understanding we mean that the unit can uniquely code (as a sequence of bits) each spoken word, interpret the word and initiate action based on the word.

Questions:

1. When u switch on your computer which software you see first and what is the utility of that software.
2. Suppose on fine day you are working on ur computer and power goes off, again u switch on our computer, what type of booting is done by that computer.
3. Write the essential parts of ur computer system without which u cant work and also list that parts which are optional.
4. How many types of storage are normally there in storage unit of a computer system? Justify the need for each storage type. Explain them.
5. What are the basic components of the CPU of a computer systems? Describe the roles of each of the components in the functioning of a computer systems.
6. Suppose an entrance exam is held and thousands of students appeared in that exam, Which device u will use to evaluate the answer sheets and why?
7. Hardware and software are like two sides of a coin. Do you agree or disagree, Give reasons.

END OF TODAYS LECTURE…

References:

1. COMPUTER FUNDAMENTALS Pradeep .K.Sinha and Priti Sinha , BPB PUBLICATIONS
2. COMPUTER ORGANISATION AND ARCHITECTURE William Stallings Prentice PUBLICATIONS

Lecture 2

GENERATIONS OF COMPUTERS

Objectives of the lecture:

1.To learn the generation of the computers.

Hello!friends , I am sure now you must be well versed with the History of computers from the previous lecture .Today I will be completing the remaining part of the previous lecture and then starting with the generations which tells how it has evolved from its early days, to become a powerful and useful tool for all types of users in today’s society. So Lets start on..

Contd.

Lets start with the defination of Pixels, the smallest dot that can be displayed is called a pixel. The number of pixels that can be displayed vertically and horizontally gives the maximum resolution of the monitor. The resolution of the monitor determines the quality of the display. The higher the resolution the better is the quality of the display. Some popular resolution are 800640 pixels, 1024768 pixels, 1280*1024 pixels.

Printer

Line printer

• It prints a complete line at a time.
• Printing speed varies from 150 lines to 2500 lines per minute with 96 to 160 character on a 15-inch line.
• Six to eight lines per vertical inch are printed.
• Usually 64 and 96 character sets are used with English letters.
• Two types of Line Printers are available.
  • Drum Printers: It consists of a cylindrical drum. The characters to be printed are embossed on its surface
  • Chain Printers: I have a steel band on which the character sets are embossed.

Serial Printers

• It prints one character at a time, with the print head moving across a line.
• They are similar to typewriters.

Apart from printers, the other output devices are given below:

1. Drum Plotter
2. Flat Bed Plotter
3. Microfilm and Microfiche
4. Graphic Display device (Digitizing Tablet)
5. Speech Output Unit

Computer Memory

Main Memory

A flip-flop made of electronic semiconductor devices is used to fabricated a memory cell. These memory cells organized as a Random Access Memory (RAM). Each cell has a capability to store one bit of information. A main memory or store of a computer is organized using a large number of cells. Each cell stores a binary digit. A memory cell, which does not loose the bit stored in it when no power is supplied to the cell, is know as a non-volatile cell.

A word is a group of bits, which are stored and retrieved as a unit. A memory system is organized to store a number of words. A Byte consists of 8 bits. A word may store one or more bytes. The storage capacity of a memory is the number of bytes it can store. The address of the location from where a word is to be retrieved or to be stored is entered in a Memory Address Register (MAR). The data retrieved from memory or to be stored in memory are placed in a Memory Data Register (MDR). The time taken to write a word is known as the Write time. The time to retrieve information is called the Access time of the memory.

The time taken to access a word in a memory is independent of the address of the word and hence it is know as a Random Access Memory (RAM). The main memory used to store programs and data in a computer is a RAM. A RAM may be fabricated with permanently stored information, which cannot be erased. Such a memory is called a Read Only Memory (ROM). For more specialized uses, a user can store his won special functions or programs in a ROM. Such ROM's are called Programmable ROM (PROM). A serial access memory is organized by arranging memory cells in a linear sequence. Information is retrieved or stored in such a memory by using a read/write head. Data is presented serially for writing and is retrieved serially during read.

Secondary or Auxiliary storage devices

Magnetic surface recording devices commonly used in computers are Hard disks, Floppy disks, CD-ROMs and Magnetic tapes. These devices are known as secondary or auxiliary storage devices. We will see some of these devices below.

Floppy Disk Drive (FDD)

In this device, the medium used to record the data is called as floppy disk. It is a flexible circular disk of diameter 3.5 inches made of plastic coated with a magnetic material. This is housed in a square plastic jacket. Each floppy disk can store approximately on million characters. Data recorded on a floppy disk is read and stored in a computer's memory by a device called a floppy disk is read and stored in a computer's memory by a device called a floppy disk drive (FDD). A floppy disk is inserted in a slot of the FDD. The disk is rotated normally at 300 revolutions per minute. A reading head is positioned touching a track. A voltage is induced in a coil wound on the head when a magnetized spot moves below the head. The polarity of the induced voltage when a 0 is read. The voltage sensed by the head coil is amplified, converted to an appropriate signal and stored in computer's memory.

• Floppy Disks com with various capacities as mentioned below.
• 5 1/4^ drive- 360KB, 1.2MB (1 KB= 2^10 = 1024 bytes)
• 3 1/2^ drive- 1.44 Mb, 2.88 MB (1MB= 2^20 bytes)

Compact Disk Drive (CDD)

CD-ROM (Compact Disk Read Only Memory) used a laser beam to record and read data along spiral tracks on a 51/4^ disk. A disk can store around 650 MB of information. CD-ROMs are normally used to store massive text data. (such as encyclopedias) which is permanently recorded and read many times. Recently CD writers have come in the market. Using a CD writer, lot of information can be written on CD-ROM and stored for future reference.

Hard Disk Drive (HDD)

Unlike a floppy disk that is flexible and removable, the hard disk used in the PC is permanently fixed. The hard disk used in a higher end Pc can have a maximum storage capacity of 17 GB (Giga Byte; 1 GB= 1024 MB = 2^30 bytes). Now a days, hard disks capacities of 540 MB, 1 GB, 2 GB, 4 GB and 8 GB are quite common. The data transfer rate between the CPU and hard disk is much higher as compared to the between the CPU and the floppy disk drive. The CPU can use the hard disk to load programs and data as well as to store data. The hard disk is a very important Input/Output (I/O) device. The hard disk drive doesn't require any special care other than the requirement that one should operate the PC within a dust-free and cool room (preferably air- conditioned).

In summary, a computer system is organized with a balanced configuration of different types of memories. The main memory (RAM) is used to store program being currently executed by the computer. Disks are used to store large data files and program files. Tapes are serial access memories and used to backup the files form the disk. CD-ROMs are used to store user manuals, large text, audio and video data.

Computer Languages

Machine language

The computers can execute a program written using binary digits only. This type of programs is called machine language programs. Since these programs use only '0's and '1's it will be very difficult for developing programs for complex problem solving. Also it will be very difficult for a person to understand a machine language program written by another person. At present, computer users do not write programs using machine language. Also these programs written for execution in one computer cannot be used on another type of computer. i.e., the programs were machine dependent.

Assembly Language

In assembly language mnemonic codes are used to develop program for problem solving. The program given below shows assembly language program to add two numbers A & B.

Assembly language is designed mainly to replace each machine code with and understandable mnemonic code. To execute an assembly language program it should first be translates into an equivalent machine language program. Writing and understanding programs in assembly language is easier than that of machine language. The programs written in assembly language are also machine dependent.

High Level Languages

High level language are developed to allow application programs, which are machine independent. High level language permits the user to use understandable codes using the language structure. In order to execute a high-level language program, it should be translated into a machine language either using a compiler or interpreter. The high level languages commonly used are FORTRAN (FOR mula TRAN slation), BASIC ( B eginner's A ll-purpose S ymbolic I nstruction C ode), COBOL ( CO mmon B usiness O riented L anguage). Recently developed programming language such as Visual Foxpro, Visual Basic (VB), Visual C++ (VC++) are more popular among the software developers. The following program written in BASIC language is to add two given numbers.

Program code Description READ A ADD B STORE C PRINT C HALT

It reads the value of A. The value of B is added with A. The result is store in C. The result in 'C' is printed. Stop execution.

Program Code Description 10 INPUT A,B 20 LET C=A+B 30 PRINT C 40 END

To read the value of A&B A&B are added and result is stored in C Print the value of C Stop execution

Computers and Communications

Local Area Network (LAN) & Wide Area Network (WAN)

Computers available in remote locations can communicate with each other using a telecommunication line. One way of connecting the computers is by using devices called modems. A modem is used to transfer data from one computer to another using the telephone lines. A modem converts the strings of 0s and 1s into electrical signals which can be transferred over the telephone lines. Both the receiving and the transmitting computer have a telephone connection and a modem. An external modem is connected to the computer like a typical input or an output device. An internal modem is fitted into the circuitry related to the CPU and Memory.

Interconnection of computers which are within the same building or nearby locations forms a network of computers and this network is called a Local Area Network (LAN). A LAN permits sharing of data files, computing resources and peripherals. Interconnection of computers located in far away locations using telecommunication system is known as Wide Area Network (WAN).