chapter 16Computer System

Organisation

INPUT OUTPUT AND MEMORY INPUT OUTPUT AND MEMORY DEVICESDEVICES

INPUT DEVICESINPUT DEVICES– KEY BOARDKEY BOARD– MOUSEMOUSE– JOYSTICKJOYSTICK

PRINTERS SPEAKERS

PRINTERSPRINTERS

IMPACT PRINTERSIMPACT PRINTERS– THERE IS MECHANICAL CONTACT THERE IS MECHANICAL CONTACT

BETWEEN THE PRINT HEAD AND PAPERBETWEEN THE PRINT HEAD AND PAPER

NON IMPACT PRINTERSNON IMPACT PRINTERS– THERE IS NO MECHANICAL CONTACT THERE IS NO MECHANICAL CONTACT

BETWEEN THE PRINT HEAD AND PAPER, BETWEEN THE PRINT HEAD AND PAPER, PRINTING WILL TAKE PLACE AS PRINTING WILL TAKE PLACE AS DIFFERENT WAYSDIFFERENT WAYS

IMPACT PRINTERS EXAMPLEIMPACT PRINTERS EXAMPLE

1. LINE PRINTERS1. LINE PRINTERS– DRUM PRINTERDRUM PRINTER

CONSIST OF CYLINDRICAL DRUM ON WHICH CONSIST OF CYLINDRICAL DRUM ON WHICH CHARACTERS ARE EMBOSSEDCHARACTERS ARE EMBOSSED

– CHAIN PRINTERCHAIN PRINTERCONSISTS OF A STEEL BAND ON WHICH ON CONSISTS OF A STEEL BAND ON WHICH ON WHICH THE CHARACTERS ARE EMBOSSEDWHICH THE CHARACTERS ARE EMBOSSED

DRUM PRINTERSDRUM PRINTERS

CHAIN PRINTERSCHAIN PRINTERS

2. CHARACTER 2. CHARACTER PRINTERS(SERIAL PRINTER)PRINTERS(SERIAL PRINTER)

– CHARACTER PRINTER PRINTS ONE CHARACTER CHARACTER PRINTER PRINTS ONE CHARACTER AT A TIME, WITH THE PRINT HEAD MOVING AT A TIME, WITH THE PRINT HEAD MOVING ACROSS A LINE, NORMALLY PRINT 30 TO 300 ACROSS A LINE, NORMALLY PRINT 30 TO 300 CHARACTERS PER SECOND.. CHARACTERS PER SECOND..

– THERE ARE TWO TYPESTHERE ARE TWO TYPES

DOT MATRIX PRINTERSDOT MATRIX PRINTERS– Printing haead contains a vertical group (array) Printing haead contains a vertical group (array)

of pins.of pins.– There are 9 pins in the print head, bottom 2 There are 9 pins in the print head, bottom 2

used to lower case, others for upper case….5 used to lower case, others for upper case….5 dot rows and 7 dot columns(5x7) format.dot rows and 7 dot columns(5x7) format.

Dot matrix printersDot matrix printers

LETTER QUALITY PRINTERSLETTER QUALITY PRINTERS– This type of printer will print full This type of printer will print full

characters not as the character made of characters not as the character made of dots.dots.

This lesson includes the following sections:

• Overview of Printers

• Dot Matrix Printers

• Ink Jet Printers

• Laser Printers

• Snapshot Printers

• Other High-Quality Printers

Overview of Printers

• Categorizing Printers

• Evaluating Printers

Overview of Printers - Categorizing Printers

Printers fall into two categories:

• Impact printers use a device to strike an inked ribbon, pressing ink from the ribbon onto the paper.

• Non-impact printers use different methods to place ink (or another substance) on the page.

Overview of Printers - Evaluating Printers

When evaluating printers, consider four criteria:

• Image quality – Measured in dots per inch (dpi). Most printers produce 300 – 600 dpi.

• Speed – Measured in pages per minute (ppm) or characters per second (cps).

• Initial cost – Consumer printers cost $250 or less, but professional printers can cost thousands of dollars.

• Cost of operation – This refers to the cost of supplies used by the printer.

Dot Matrix Printers

• How Do Dot Matrix Printers Work?

• Performance

Dot Matrix Printers -How Do Dot Matrix Printers Work?

• Dot matrix printers are a common type of impact printer.

• A dot matrix printer's print head contains a cluster of pins. The printer can push the pins out

to form patterns in rapid sequence.

• The pins press an inked ribbon against the paper, creating an image.

Dot Matrix Printers - Performance

• Lower-resolution dot matrix printers use nine pins. Higher-resolution models have 24 pins.

• Speed is measured in characters per second (cps). Some dot matrix printers print 500 cps.

Ink Jet Printers

• How Do Ink Jet Printers Work?

• Performance

Ink Jet Printers – How Do Ink Jet Printers Work?

• Ink jet printers are an example of non-impact printers.

• The printer sprays tiny droplets of ink onto the paper.

• Ink jet printers are available for color and black-and-white printing.

Ink Jet Printers - Performance

• Ink jet printers offer speeds of (2 – 4 pages per minute ppm) and resolution (300 – 600 dots per inch dpi), comparable to low-end laser printers.

• Ink jet printers are inexpensive and have low operating costs.

Laser Printers

• How Do Laser Printers Work?

• Performance

Laser Printers – How Do Laser Printers Work?

• Laser printers are non-impact printers.

• They use heat and pressure to bond particles of toner to paper.

• Laser printers are available for color and black-and-white printing.

Laser Printers - Performance

• Laser printers provide resolutions from 300 – 1200 dpi and higher.

• Black-and-white laser printers usually produce 4 – 16 ppm.

• Laser printers produce higher-quality print than ink jet printers, but are more expensive.

Snapshot Printers

• Snapshot printers are specialized, small-format printers that print digital photographs.

• Snapshot printers are fairly slow, and can be more expensive to operate

Snapshot printers are popular among digital camera users

Other High-Quality Printers

Print shops and publishers use these printers to create high-quality color images:

• Thermal-wax

• Dye-sublimation

• Fiery

• IRIS

• Plotters

Plotters use mechanical, ink jet, or thermal technologyto create large-format images for architectural or engineering uses.

Review

• List the three most commonly used types of printers.

• List the four criteria you should consider when evaluating printers.

• Describe how a dot matrix printer creates an image on a page.

• Explain the process by which a laser printer operates.

• List five types of high-quality printing devices commonly used in business.

 

 

AN ESSENTIAL COMPONENT OF EVERY COMPUTER IS ITS MEMORY

EACH AND EVERY WORD IS ASSIGNED AN ADDRESS IN THE MEMORY.

EACH WORD CONSISTS OF SAME BITS IS CALLED WORD LENGTH. MEMORIES CAN BE READ FROM OR WRITTEN INTO MEMORIES THAT CAN BE BOTH READ FROM AND WRITTEN INTO

ARE CALLED READ-WRITE MOMORIES. SOME MEMORIES HAVE PROGRAM OR DATA PERMANENTLY

STORED AND ARE CALLED READ ONLY MEMORY. THERE ARE TWO TYPES OF MEMORY DEVICE

PRIMARY MEMORY (RAM, ROM) SECONDARY MEMORY (HARD DISK, FLOPPY, CD, PEN DRIVE)

THERE ARE TWO TYPES OF RAM DYNAMIC RAM (DRAM) STATIC RAM(SRAM)

DRAM CONSISTS OF A TRANSISTOR AND CAPACITOR. CAPACITOR THAT’S CAPABLE OF STORING AN ELECTRIC

CHARGE DEPENDING ON THE SWITCHING ACTION OF THE TRANSISTOR.

CAPACITOR EITHER CONTAIN NO CHARGE (0 BIT) OR DOES HOLD A CHARGE (1BIT)

DRAM PROVIDES VOLATILE STORAGE IT MEANS IF POWER FAILURE MEANS IT WILL LOST ITS MEMORY

DRAM CONTAINS TWO ELEMENTS MOSFET (METAL OXIDE SEMICONDUCTOR

FIELD EFFECT TRANSISTOR) CAPACITOR EACH CHIP WILL HAVE THE STORAGE

CAPACITY OF 64 BIT.

THE AMOUNT OF TIME TAKEN TO PRODUCE DATA REQUIRED FROM MEMORY, FROM THE START OF ACCESS UNTIL THE AVAILABLILITY OF DATA IS CALLED MEMORY ACCESS TIME.

DRAM CHIPS HAVE ACCESS TIME RANGING FROM BELOW 7 TO 70 NANOSECONDS.

DRAM CELL CONSISTS OF ONLY ONE TRANSISTOR AND CAPACITOR PER BIT

GENERALLY DRAM CHIPS ARE AVAILABLE WITH 128 BIT OR 256 BIT DENSITIES OR MORE

THE PROBLEM OF CAPACITOR IS THAT IT STARTS LOSING THE CHARGE OVER A PERIOD OF TIME

THEREFORE THE MEMORY CONTROLLER NEEDS TO REFRESH THE MEMORY CONTENTS AS MANY AS THOUSAND TIMES A SECOND, WHICH IS CALLED MEMORY REFRESHING.

EDO DRAM Extended Data Out Dynamic Random Access Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU.

It has a dual pipeline architecture

BECAUSE OF NUMBER OF WIRES IN A SINGLE CABLE(MULTIPLEXING) , EDO DRAM CHIPS CANNOT OPERATE IN LOCK AND STEP INTO THEIR HOST MICROPROCESSORS.

THIS IS CALLED ASYNCHRONOUS MEMORY PERFORMANCES

THIS WILL KEEP THE MEMORY BUS SPEED LIMITED TO 66MHz.

TO REDUCE THIS PROBLEM, IT WAS MADE POSSIBLE BY REDESIGNING THE BASIC MEMORY CHIP INTERFACE CALLED SYNCHRONISED DRAM

RAMBUS DRAM DOUBLE DATA RATE (DDR) SDRAM

THIS RAM IS FAIRLY FAST, AND IT WIL TRIED TO ADDRESS SOME OF THE COMPLEX ELECTRICAL AND PHYSICAL PROBLEMS INVOLVED WITH MEMORY.

RDRAM IS NOT MULTIPLEXING, RATHER THAN IT CREATES INDEPENDENT CONTROL.

SDRAM WIL SUPPORTS ONE OPERATION IN EACH CLOCK CYCLE,

BUT DDR SDRAM CAN DO TWO OPERATION PER CLOCK CYCLE

SO THAT IT HAS DOUBLING THE MEMORY BANDWITDTH

IT IS ALSO A VOLATILE BUT AS LONG AS THEY ARE SUPPLIED WITH POWER.

THAT MEANS IF POWER GOES MEANS IT WILL STORE THE BINARY FORMAT OF CONTENTS, IT WILL REMAINS TO THE SYSTEM WHEN POWER IS APPLIED TO THE SYSTEM.