This chapter discusses computer input and output devices, monitors, and printers. It covers the major components like the keyboard, mouse, trackball, touchscreen, and scanners for input. For monitors, it explains size, resolution, refresh rate, and dot pitch. It also covers LCD, inkjet, and laser printers. The chapter concludes with an overview of serial, parallel, and SCSI interfaces that allow communication between devices and the computer system.

1. Chapter 3
Peter Norton’s Introduction to Computers
Interacting with Your
Computer

2. Input Devices:
• Keyboard
• Mouse
• Trackball
• Trackpad
• Pen
• Touch Screen
• Bar Code Reader
• Image Scanner
• Microphone
• Video

3. Factors Affecting
Monitors:
• Size
• Resolution
• Refresh rate
• Dot pitch

4. Size is measured
diagonally.
Resolution = no. of pixels
(i.e. 1024 x 768)
Image clarity or sharpness
Refresh rate = number of
Times persecond that the
electron gun scans every
pixel on the screen
frames in one second
The picture is scanned
from left to right and
from top to bottom.
One complete set of scan
lines is called a frame.
1 pixel in a color monitor

5. Flat-Panel Monitors:
• LCD (Liquid Crystal Display)
(Notebooks use LCD displays)

6. Types of Printers:
• Ink Jet Home and Offices
• Laser Home and Offices
• Dot-Matrix Home and Office
• Plotter Commercially
used for printing
of sign boards or
large images

7. Ink jets are popular because of their
relatively low cost and color capability.

8. Paper is given a
static charge
Laser beam
Heat roller bonds
toner to paper
Toner transferred
from drum to paper
Rotating
mirror
Laser transfers
image to drum
Laser printers are faster and capable of high resolution.

9. Printer Criteria:
• Image Quality DPI
• Speed PPM
• Initial Cost Normal
• Cost of Operation Normal

10. Machine Cycle
• Fetching
CU receives command / data from memory
• Decoding
CU breaks down commands into instructions
• Executing
After command execution CPU converts them into
microcode
• Storing
CPU stores results into memory

11. Types of Interfaces:
• Serial
• Parallel
• SCSI (Small Computer System Interface)

12. Bit 0Start bitBit 1Bit 2Bit 3Bit 4Bit 5Bit 6Bit 7Stop Bit
RS232
Driver
To modemTransmitter
Receiver
Control Serial data transmission
is relatively slow!
The serial ports transfer data one bit at a time.

13. Transmitter
Receiver
Control
To printer
The parallel port transfers data one byte at a time.
Drivers

14. A SCSI card can be plugged
into an expansion slot. SCSI
devices can be daisychained.

16. The major computer system components (processor, main
memory, I/O modules) need to be interconnected in order to
exchange data and control signals
A bus is a communication pathway connecting two or more
devices
A bus that connects major computer components (processor,
memory, I/O) is called a system bus.
Bus = a shared transmission medium. Only one device at a
time Can successfully transmit.
shared system bus consisting of multiple lines
a hierarchy of buses to improve performance.
Key design elements for buses include: Arbitration, Timing,
width

18. Program
A sequence of (machine) instructions
(Machine) Instruction
A group of bits that tell the computer to perform a specific operation
(a sequence of micro-operation)
The instructions of a program, along with any needed data are stored in
memory
The CPU reads the next instruction from memory
It is placed in an Instruction Register (IR)

19. A computer instruction is often divided into two parts
An opcode (Operation Code) that specifies the operation for that
instruction
An address that specifies the registers and/or locations in memory
to use for that operation
In the Basic Computer, bit 15 of the instruction specifies the
addressing mode (0: direct addressing, 1: indirect addressing)
Since the memory words, and hence the instructions, are 16 bits long,
that leaves 3 bits for the instruction’s
Opcode Address
Instruction Format
15 14 12 0
I
11
Addressing
mode

20. Learning Objectives:
Chapter 3 Review
• List at least three common input and output devices.
• Name the processes a video monitor uses to displays images.
• Name the components of a mouse and list the common
techniques used to maintain a mouse.
• Name three types of printers and list the advantages and
disadvantages of each.
• Explain how input and output devices communicate with the
other parts of the computer.