Unit -1

1. Unit -1

2. Digital Computer • It is a processing machine that process the information in digital form i.e. (0’s & 1’s). • Means digital computer can only understand binary language (0’s & 1’s). • If any analog quantity is to be processed, they must be converted into digital form before processing

3. Digital computer Process • The block diagram of a digital computer is shown below. Whatever may be the type, size and capacity of the computer, it should have these five blocks. Input Processing Output

4. Digital Computer Functional Unit Input Devices Storage Output Unit Control Unit ALU

5. Functional units of computer • The computer consists of four main parts. These are as follows: (i) Central processing unit.(ii) Memory(iii) Input Devices (iv) Output devices

6. CPU • Central Processing Unit The CPU is the place where computations are performed. It is the brain and heart of a computer. • CPU interprets instruction and process data contained in computer program. • CPU has two component • ALU ( Arithmetic & Logic Unit) • CU ( Control Unit ) The arithmetic logic unit (ALU) of the CPU performs the typical arithmetic operations such as addition, subtraction, multiplication, and division. Computers use the binary number system, to represent numbers. The binary number system has only two digits 0 and 1. Control Unit control all the operation in computer. It is the controller of the system. • It also control all the devices connected to CPU. • It also control the flow of data from i/p devices to memory and memory to o/p devices.

7. Memory • Memory: Memory is the location where data and programs are stored while being processed by the CPU. Memory is the main storage unit in a computer. Memory consists of primary (main) memory and secondary memory. The data stored in main memory (RAM) is volatile and is erased as soon as the power supply is cut off. Therefore, secondary memory is used to store data. In secondary memory (diskettes) data is stored permanently.

8. Input Devices • Input Devices: Input is the process of entering and translating incoming data into machine readable form. • Any hardware item which attached to the main unit of a computer that houses the CPU is referred to as peripheraldevice. • An input device is a peripheral device through which data are entered and transformed into machine readable form. Input devices are mainly used to communicate information between humans and computer. Example: Keyboard, CPU etc.

9. Output devices • Output Devices: An output device is a peripheral device that allows a computer to communicate information to humans or another machine by accepting data from the computer and transforming them into a usable form. The output devices gives the desired result to the user. Example: Monitor, Printer etc.

10. BUS

11. BUS • A group of wires connecting two or more devices and providing a path to perform communication is called bus. • A bus that connect major computer component such as ( CPU , Memory , I/O) is called system bus

12. Bus • A bus is a set of physical connections (cables, printed circuits, etc.) which can be shared by multiple hardware components in order to communicate with one another. • The purpose of buses is to reduce the number of "pathways" needed for communication between the components, by carrying out all communications over a single data channel. This is why the metaphor of a "data highway" is sometimes used.

13. Bus

14. Characteristics of a bus • A bus is characterised by the amount of information that can be transmitted at once. This amount, expressed in bits, corresponds to the number of physical lines over which data is sent simultaneously. A 32-wire ribbon cable can transmit 32 bits in parallel. The term "width" is used to refer to the number of bits that a bus can transmit at once. • Additionally, the bus speed is also defined by its frequency (expressed in Hertz), the number of data packets sent or received per second. Each time that data is sent or received is called a cycle.

15. Characteristics of Bus • This way, it is possible to find the maximum transfer speed of the bus, the amount of data which it can transport per unit of time, by multiplying its width by its frequency. A bus with a width of 16 bits and a frequency of 133 MHz, therefore, has a transfer speed equal to: • 16 * 133.106 = 2128*106 bit/s, • or 2128*106/8 = 266*106 bytes/s • or 266*106 /1000 = 266*103 KB/s • or 266*103 /1000 = 266 MB/s

16. Kinds of bus inside the System There are three main bus groups or System bus can be separated into three functional group • ADDRESS BUS • DATA BUS • CONTROL BUS

17. Data Bus • The Data Bus carries the data which is transferred throughout the system. • It is bi-directional. • Examples of data transfers • Program instructions being read from memory into MPU. • Data being sent from MPU to I/O port • Data being read from I/O port going to MPU • Results from MPU sent to Memory • These are called read and write operations Data Bus

18. Address Bus • An address is a binary number that identifies a specific memory storage location or I/O port involved in a data transfer • The Address Bus is used to transmit the address of the location to the memory or the I/O port. • The Address Bus is unidirectional (one way): addresses are always issued by the MPU. Address Bus

19. Control Bus • The Control Bus: is another group of signals whose functions are to provide synchronization (timing control) between the MPU and the other system components. • Control signals are unidirectional, and are mainly outputs from the MPU. • Example Control signals • RD: read signal asserted to read data into MPU • WR: write signal asserted to write data from MPU Control Bus

20. Single Bus system

21. Computer Generations • Generation • A leap into hardware and software development. Core Vacuum tube Integrated Circuit Transistors

22. Computer Generations First Generation (1942-55) • They were the fastest calculating devices of their time. • They were too Bulky. • They used thousands of vacuum tubes for circuitry and magnetic drums for memory. • They generated a lot of heat. • They consumed a lot of power. • Their hardware failed frequently because of the vacuum tube filament failure. • They required frequent maintenance due to low-mean time between failure. • Their commercial production was difficult . • Hardwired programming was used to program them.

23. Computer Generations Second Generation (1955-1964) • In these computers transistors replaced the vacuum tube. • Transistors made them ten times faster than Ist generation computers. • They should be kept air-conditioned room. • They consumed power less than 1st generation computers. • They were realizable and less prone to failure. • They had larger and faster primary & secondary memories. • They were easier to program using programming language (FORTRAN, COBOL, RPG, ALGOL, SNOBOL, …) • Commercial production was difficult. • They used batch operating systems. • They had increased commercial use.

24. Computer Generations Third Generation (1964-75) Their commercial production was easier and cheaper. There software were portable. They used timesharing operating systems. They supported Interactive usage. They supported on-line computing. Timesharing improved the programmer’s productivity. Supported unbundling of hardware and software. Minicomputers were introduced. • They performed more than a million instructions per second. • They were of smaller size. • They needed air-conditioned rooms. • The consumes less power. • They were very reliable and needed less maintenance. • They had larger and faster primary and secondary memories. • They were general purpose computers (scientific and commercial use).

25. Computer Generations Fourth Generation (1975-89) Office and home computing. They were networked so allowed distributed computing. Allowed ad-on hardware and software. Their affordability allowed individual ownership. • Personal computers (PC) were smaller. • Mainframe were more powerful. • No AC for PC. • Much less power consumption. • Extremely reliable. • Much faster and bigger primary and secondary memory. • Totally general purpose. • Much easier production • Portable software. • Used Graphical Interface (GUI),

26. Computer Generations Fifth Generation (1989- Present) They are automatically production. Portable software. More user-friendly. Very versatile as they can be used almost in every walk of the life. Internet-based computing. Unbundled software and ad on hardware. True user friendly as they are being used by a variety of users ranging from a child to a scientist. • Portable PC (Notebook and laptops) • Desktop and workstation PC. • More faster mainframe computers. • PCs and laptops operate at room temperature. • They consume optimal power. • Extremely reliable and very fast. • Hot-pluggable feature (replace parts without shutting down) • Truly general purpose,

27. Computer Generations

28. Computer Generations