1. technology and computing
2. hardware
3. computer

Major Hardware Components of
a Computer System
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Central Processing Unit
Auxiliary Storage
Input Devices
Output Devices
Central Processing Unit
• Arithmetic/Logic Unit (ALU): processes data
arithmetically (addition, subtraction,
multiplication, division) or logically (greater than,
less than, equal to)
• Control Unit: works with the operating system to
move data between auxiliary storage and main
memory; and between main memory and the ALU
• Main Memory: contains both program instructions
and the data that is required.
• A single machine can have multiple CPUs to
share processing tasks (co-processors,
multiprocessing), but each CPU can execute only
a single task.
Inside the System Unit
• Main component: motherboard
– Circuit board that “houses” integrated circuits
(microscopic elements … wires, transistors,
etc…) required to make the digital pulse flow
inside of the computer. Pulses flow from
component to component via the “bus”
– Some microcomputers contain a special local
bus (VESA or PCI) which increase data transfer
rates to the display and/or storage devices
Motherboard (cont.)
– Attachments to the motherboard include:
• Main Memory: types of main memory include:
– RAM - temporary (includes virtual memory storage). Include RAM
cache
– ROM - permanent
– CMOS - semipermanent battery powered
» Memory chips attach with either a DIP (dual inline pin - old PCs)
or as a SIMM (single inline memory module) board
– When add main memory, make sure add-on chips are compatible
• Real time clock (current date and time)
• Microprocessor or CPU (central processing unit)
– Control Unit: traffic cop portion of the CPU
– ALU: arithmetic logic unit processes all math and logical operations
performed by the computer
Motherboard (cont.)
• Expansion slots/add on boards - allow “cards” that attach
various peripheral devices to the motherboard
– monitors, hard drive, internal fax/modem, network cards,etc
– PCMCIA slots: special slots developed for laptops to attach
devices and add on RAM
• Expansion devices may provide an external “port” which you
connect a cable to. Device ports will either be from an internal
or external bay in the system unit.
– Serial Port: transmits data one bit at a time (modem)
– Parallel Port: transmits 8 bits simultaneously (printers, backup
devices, etc.)
– SCSI Port: allows several devices to be chained together and
connected through a single SCSI (small computer system
interface)
– MIDI Port: musical instrument digital interface
Main Memory
• Random Access Memory (RAM): allows data
and instructions to be accessed randomly from any
memory location (address). Primary storage.
– Volatile - lost when power is turned off
• Read Only Memory (ROM): usually contains
programs that help the computer system operate:
– can only be read: cannot be written to or altered by the
user (usually)
– ROM is not volatile
Main Memory
• Data and instructions are stored as BITS (binary
digits). Everything from our world is translated
into a computer recognizable format called binary
(zeros or ones)
– The combination of binary digits represents our letters
or numbers. One character represented is equal to a
byte.
• Memory capacity is measured in bytes. Today’s
most common measurement is megabytes
Kilo = 1,000 (KB) Thousand
Mega = 1,000,000 (MB) Million
Giga = 1,000,000,000 (GB) Billion
• Bytes are composed using either the ASCII
coding system (7 bits = character) or EBCDIC (8
bits = character)
Microprocessor Families
• Intel (IBM) and Motorola (Macintosh
68000) two main manufacturers
• Microprocessors are “families” - upward
increases in speed (early SX vs DX chips)
• Increase in bus capacity indicates a new
generation
The Boot Process
• When you turn your computer on, the following
activities happen:
– Power is sent to the internal fan and the motherboard
– The boot program stored inside of ROM activates
– The Power-On Self-Test (POST)runs and tests required
system components
– The operating system/environment is loaded
– Configuration and customization routines are executed
which set your computer environment
Input/Output Peripheral Devices
• Badge Reader
• Bar-code Reader
• Cartridge & cassette
drives
• CD Rom
• Digital camera
• Digital tables & scanners
• Keyboard, mouse, pens
• MICR
• Voice
• OCR
• Touch screen
• SASD & DASD drives
• Printers
– Page vs line or character
printers
– Impact vs nonimpact
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Plotter
Robotics
Speech synthesizer
VDT
Microforms
Storage
Required because main memory is limited, expensive
and volatile.
• Sequential Access Storage Devices (SASD): data is stored
in sequential order. Retrieval is also sequential.
– Storage media is magnetic tape.
– Supports batch processing environment
– Excellent form of backup
• Direct Access Storage Devices (DASD): data can be stored
and retrieved randomly.
– Storage capacity is referred to as density. How tightly
packed data is on the disk.
– DASD is required for transaction processing.
• Memory capacity is measured in bytes. Today’s most
common measurement is kilobytes, megabytes and gigabits.
Printer Considerations
• Dot matrix - low price & inexpensive to
operate. Lower quality. Impact - can print
carbon forms. Color option. Slow.
• Ink jet - moderate price & better output.
Color option. Nonimpact. Quieter.
• Laserjet - more expensive. Faster. High
quality. Nonimpact.
Display Considerations
• Screen size- diagonal measurement from corner to
corner. Popular sizes are 14”, 15” and 17”
• Dot pitch - measure of image clarity. The smaller
the dot pitch, the crisper the image or resolution.
• Video adapters/cards impact image resolution and
display speed. Today, most monitors are Super
VGA (1024 x 768)and use non-interlaced
projection technology (flicker)
• Laptop - liquid crystal display (LCD). Passive
matrix vs active matrix screen (display method
which impacts image quality). Active matrix is
much better but more expensive and can have
problems.
DASD
• Floppy Disk: removable DASD. Most common
density is 1.44Mb.
• Hard Disk: usually don’t remove (but newer
devices you can). Higher storage capacity than
floppy disks. Faster access.
– Winchester drive architecture is not removable.
– Can be drives that have removable disk platters.
– Optical disk: CD_ROM (read-only) Erasable optical
disk is also available. WORM - write once, read many.
– Flash memory: main memory on a card. Non volatile.
PCMCIA card.
DASD cont.
• All data stored on DASD media is stored in pieshaped sectors that determines how much data is
moved into and out of main memory at a time.
• Virtual storage: operating system uses hard disk
drive as an extension of main memory.
• Cache memory: operating system assumes that
most data used by an application is accessed over
and over again. Cache is a special area in main
memory where such data is put instead of paging
it back and forth to DASD.
DASD cont
• WORM: write-once, read many. (CD
ROM). Also have rewriteable CD ROM.
• Floptical Disk: optical storage capacities on
floppy disk.
• DVD: Digital video disk
• Hierarchical Storage: use of many different
types of DASD & SASD devices to achieve
storage requirements.
Other considerations:
• Desktop vs Laptop - expansion slots and
capability
– Port replicators vs docking station
– Pointing device. Track ball, touch pad, erase point.
– Power management & battery considerations (hot
swap)
• Multimedia devices - sound cards, speakers and
MPC standards
• Bundled software
Common File Types
• Data Files: files of information created when
people use various types of software
• Executable Files: Types of systems files that are
used by the computer to perform certain tasks.
With some executable files (.exe., .com, .bat) you
can initiate the processing while with others the
computer initiates the process (.dll, .sys, .drv, etc.)
• You and your AUTOEXEC.BAT file.
Anatomy of a Filename
• Rules for creating valid filenames
(appropriate characters, length of names,
etc.) depends on the operating system being
used.
• Components of a filename consist of:
File name from
you
Drive Designation
C:/foldername/filename.ext
Folder/subdirectory
name
File extension
supplied by the
program
File Storage
• Logical Storage:
How you perceive that data
is stored on an auxiliary
storage media
• Physical Storage
How data actually
resides on your
auxiliary storage
media
File/disk directory
No indication of
fragmentation
File Allocation Table
(FAT)
Fragmentation is normal
Measurements of Computer Power
• Clock speed: electronic pulses used to
synchronize processing. Faster clock speeds result
in more operations in a give amount of time.
Measured in megahertz (MHz).
• Bus width: determines how much data can be
transferred at any one time. 16 bit, 32 bit, 64 bit.
– IBM’s Microchannel (MCA) Architecture vs EISA
(open architecture)
• Word size: number of bits/bytes manipulated at
once. Same as the bus width.
• Other determinants include main memory
capacity, MIPs.
• This is not the same as throughput but it can affect
throughput..