Chapter:1 Computer System Organization

1. Chapter:1 Computer System Organization =>Input Device: A device used to provide data and instruction to the computer are called input device. Example: keyboard 1.Keyboard: It is used to enter both numeric al and character type data. it is like a mechanical typewriter with alphanumeric and special keys.

2. =>Types of Keyboard There are two type of keyboard 1.Serial keyboard 2.Parallel keyboard =>A serial Keyboard is one which communicates the data to the central processing unit one bit a time. that is the bit pattern that forms a particular character is sent on a single wire.

3. A parallel Keyboard carries one byte(8bits) at a time to the central processing unit. • The bit pattern that forms a character is sent on 8 different wires. • Microphone(MIC): It is used to record sound. It convert sound waves into audio signals.

4. Mouse: It is small hand held pointing device connected to CPU through a cable. • It has a rotating ball at bottom and has two click buttons on the top. As the mouse is moved across a rubber pad or a flat surface, the ball rolls and its movement is converted into electrical signal and communicated to CPU. these movements are interpreted and display on the screen as an arrow.

5. Many styles of trackball are available • Output Device: When the data and instructions are fed to the computer and processed, the next step is to get the output. This output may be displayed on the monitor or printed on the paper

6. Monitors - Categories of Monitors Monitors are categorized by the technology they use: • Cathode ray tube (CRT) monitors • Flat-panel displays And by the way they display colors: • Monochrome – One color on a black background • Grayscale – Shades of gray on a white or off-white background • Color – From 16 to 16 million unique colors

7. Monitors - CRT Monitors • In CRT monitors, electrons are fired at phosphor dots on the screen. • The dots are grouped into pixels, which glow when struck by electrons. • In color CRTs, each pixel contains a red, green, and blue dot. These glow at varying intensities to produce color images. • =>TFT(Thin Film Transistor) is a device within each pixel that sets the charge

9. Monitors - Flat-Panel Monitors • Most flat-panel monitors use liquid crystal display (LCD) technology. • Passive matrix LCD uses a transistor for each row and column of pixels. • Active matrix LCD uses a transistor for each pixel on the screen. • Thin-film transistor displays use multiple transistors for each pixel.

10. Flat-panel monitors take up less desk space.

11. Printer: A printer is an output device which is used to transfer output data from a computer onto paper. • Types of Printer • There are two types of Printer 1.Impact Printer: There is mechanical contact between the print head and paper.

12. 2.Non-Impact Printer: There is no mechanical contact between the print head and paper. • Impact Printer divided into Two parts. 1.Line Printer 2.Character Printer(Serial Printer) • Line Printer prints a complete line at time • Types of Line Printer • There are two types of Line Printer • Drum Printer:a drum printer consists of a cylindrical drum on which characters are embossed.

13. Chain printer: A chain printer consists of a steel band on which the characters are embossed. To print a line, the characters in line are transmitted from the memory to printer buffer. • Character printers(Serial Printer): Serial character printer print one character at a time ,with the print head moving across a line • Serial Printer divided into Two Parts.

14. 1.Dot Matrix Printers: The printing head contains a vertical array of pins. As the head moves across the paper, selected pins free against an inked ribbon to form a pattern of dots on the paper. • 2. Letter Quality Printers:The letter quality printers print full characters (continuous character not as the character mode of dots)

15. Non-Impact Printers: The limitations of speed in electromechanical device and cost considerations have led to the development of printers called non-impact printers. • Type of Non-Impact Printers 1.Electromagnetic printers: A magnetic image can be written on a drum surface. then this surface is passed through magnetic powder which adheres to charged areas.

16. The powder is pressed onto the paper. 2.Thermal Printers: An electric pulse can be converted to heat on selected sections of a printing head or on wires or nibs(heads). When this head is applied to head sensitive paper, a character is printed. 3. Electrostatic printers: The paper is coated with a non conducting dielectric material which holds charges when voltages are applied

17. with writing “nibs” (heads). these heads write dots on the paper as it passes. Then the paper passes through a toner which contains material with colored particles carrying an opposite charge to that written by the nibs as a results, particles adhere to the magnetized areas, forming printed characters. 4. Inkjet printers: It is a character printers, which form characters and all kinds of images by spraying small drops of ink on to the paper. The print head of an inkjet printer contains up to 64 tiny nozzles.

18. Laser printer: Laser printers are page printers, which print one page at a time. The main components of a laser printer are a laser beam source, a multi-sided mirror, a photoconductive drum and toner. • 1.High speed 2.High quality output. • 1.Cost. 2.maintenance cost is high.

19. Memory Primary (Main) Memory Auxiliary (Secondary) Memory RAM Memory ROM Memory Static Memory Dynamic Memory Masked ROM PROM EROM EEROM • Memory • Essential component of computer, stores data, programs and results. • Three kinds of memory in modern computers: • 1.Semiconductor 2.Magnetic 3.Optical memories • Types of memories • 1.Main memory 2.Secondary (Auxiliary) memory

20. Semiconductor Memory Magnetic Optical WORM ROM RAM CD-ROM HARD DISK FLOPPY DISK TAPE

21. Speakers: Speakers receive the sound in form of electric current from the sound card and then convert it to sound format. • Memory: Memory is a device where data and instructions are Stored and retrieve. • Bit : A bits is a binary digit either a 0 or 1. • Byte: A byte is a basic unit of memory • A sequence of 8 bits. • Word: A sequence of 16 bits or 2 bytes.

22. Types of Memory 1.Main memory 2.Secondary memory 3.Cache Memory • Main memory: It is the place where the data and instructions supplied by the input devices are stored. • It is a temporary because the data and instructions stored are eased when power cut off.

23. Types of Main memory • There are two types of main memory. 1.RAM(random Access Memory) 2.ROM(Read Only Memory) • RAM: It is the read and write memory. It is like a page notebook, where write something to or read something from. • Any memory location is accessed randomly for reading and writing.

24. It is a temporary because the data and instructions stored are eased when power Failure. • It is also known as Volatile Memory. • It is Two Types • 1.Static • 2.Dynamic • Both are volatile

25. RAM • Dynamic RAM made from MOS. Charge must be continually refreshed in order to maintain data. However, it is cheaper, more compact than Static RAM. • Dynamic Ram used for most primary memory. Amount of data per chip has increased rapidly.

26. RAM • Static RAM is expensive, but does not need to be refreshed, and is faster. Much smaller data capacity on a chip (~256 k). • Generally made using bipolar technology, although recently have developed MOS static RAM. • SRAM is often used for cache memory, because of its faster access time.Rom:It is a permanent memory. The data is stored permanently and cannot be altered by the programmer. It is also known as Field Stores or Dead Stores.

27. Types of ROM 1.PROM(Programmable Read-Only Memory): It is initially empty. Later, the user can store programs ,data or any other information permanently. However, these programs cannot be erased once they are written to it. 2.EPROM(Erasable Programmable Read-Only Memory): The Contents stored in this can be erased by exposing it to ultra violet light source for about 10-20 minutes.

28. then it is progammed,that is new information can be stored. 3.EEPROM(Electrically Erasable Programmable Read-Only Memory): The contents stored in this can be erased electrically. Later new information is stored in it. • It is also known as Flash Memory. • Cache Memory: It is a high speed memory and placed between the CPU and the main memory.

29. Users cannot access this memory. it stores data and instructions that are currently to be executed. • Cache memory contains a copy of frequently used data/programs from main memory (ie it duplicates some contents). When the CPU attempts to read a word of memory , a cache controller checks to determine if the word is in cache. • If present then word delivered to CPU (called a hit); else (a miss) gets block from main memory and loads it into cache, preserving locality of execution. • Hit ratio is hits to total requests

30. There are two types of cache Memory; • Level 1(L1) cache • Lever 2(L2) cache • The L1 Cache is built inside the CPU package while the L2 cache is external to the CPU and resides on the motherboard. • Both L1 and L2 cache have been integrated within the cpu package to reduce access time and improve system performance further. the L2 cache on the motherboard works at motherboard bus speed while the L1 cache inside the cpu works at half the cpu clock speed.

31. Secondary Memory: secondary storage devices are used to store large amount of data permanently. • Types • 1.Floppy Disks • 2.Hard Disks • 3.Magnetic tapes • 4.Magnetic drum • 5.CD-ROM

32. Magnetic Disks • A magnetic substance is coated on a round surface • The magnetic substance can be polarized in one of two directions with an electromagnet (“writing data”) • The electromagnet can also sense the direction of magnetic polarization (“reading data”) • Similar to a read/write head on a tape recorder (except the information is digital rather than analogue)

33. Floppy Disks • Also called “flexible disks” or “diskettes” • The platter is “floppy”, or flexible (e.g., mylar) • Most floppy disk drives can hold one diskette (two surfaces) • The diskette is removable • Typical rpm: 300, 360 • Capacities: 700 KB to 1.4 MB (& up to 100 MB “zip” disks)

34. Floppy Disk Example Shutter Access window Cutawayshowing disk Case Spindle Writeprotect tab

35. Hard Disk Example

36. Hard Disk Layout Head Block Headmotor Platter Sector Track Cylinder Track Drivemotor Head, onmoving arm Head assembly

37. Locating a Block of Data Seek Time Latency Time Transfer Rate Latency Transfer Head Seek Desiredtrack Note: Access time = seek time + latency

38. Terminology • Platter • A round surface – the disk – containing a magnetic coating • Track • A circle on the disk surface on which data are contained • Head • A transducer attached to an arm for writing/reading data to/from the disk surface • Head assembly • A mechanical unit holding the heads and arms • All the head/arm units move together, via the head assembly • Cylinder • A set of tracks simultaneously accessible from the heads on the head assembly

39. Hard Disk: Concentric circles on the magnetized surface of the magnetic disks are known as Tracks. • Each track is dived into 8 parts. • Each of the 8 parts of a track is called a Sector. • Sectors: The Tracks on the disk surface are divided into invisible segments known as sectors.

40. Cylinder: Similar numbered tracks on different platters of a hard disk form a cylinder. • Digital Video Disk or Digital Versatile Disk(DVD): DVD is a optical storage device .It store more information and transfer it to the computer very fast as a CD-ROM. • DVDs come in two Formats: • 1.DVD-Video Format • 2.DVD_ROM Format.

41. NOTE: In General ,Memory refers to internal memory and Storage refers to external memory. • 1Byte=8 bits. • 1 MB=1024 Bytes. • 1 GB=1024MB

42. Communication Bus Ports • Serial Ports. Transfer data serially a bit at a time. • Parallel Ports. It can receive or send a byte at a time. • USB Ports. • AGP Ports. Connect to graphic card. Address Bus (16 lines): They carry memory address. Data Bus (8 lines): It carries data in binary form,between the processor and other external units. Control Bus: These have specific functions for coordinating and controlling micropocessor operations.

43. Infrared Ports. It sends or receive infrared • Signals from other devices. • BlueTOOTH. It describes how mobile phones • and PDA can connected through short range • wireless connection. • Network Ports.It are used to enabled • Communications Between programs. • Phone Ports. Is a port that allows connecting • telephone equipment with the computer sound card.