1. Stuart Cunningham - Computer Platforms - 2003
COMPUTER PLATFORMS
Input, Output, and Storage
&
Introduction to Basic Computer
Architecture
Week 2
2. Stuart Cunningham - Computer Platforms - 2003
Week 2
• Input, Output, Storage
– Devices
– Media
• Computer Architecture
– The CPU
• ALU
• Control unit
• Registers
– Buses
– Von-Neumann
3. Stuart Cunningham - Computer Platforms - 2003
Input
• Sending information to the computer
• Issuing the computer with a command
• Devices for Input
• Keyboard
• Mouse
• Scanner
• Camera
• Joystick / Gamepad
• Microphone (Transducer)
• Lightpen
• Barcode Reader
• Fingerprint Scanner
4. Stuart Cunningham - Computer Platforms - 2003
Output
• Returning the result of a process
• Querying the user
• Providing the user with feedback
• Devices for Output
• Monitor
• Printer
• Plotter
• Digital Projector
• Speakers
• Synthesiser
• Robot / Machine
• LED’s
5. Stuart Cunningham - Computer Platforms - 2003
Storage
• Place to keep important data
• Kept on a storage medium
– Magnetic, Optical, physical
• Devices for Storage
• Hard Disk Drive (HDD)
• Floppy Disk Drive (FDD)
• Zip Drive
• Tape Drive
• CD / DVD (ROM, RW, R)
• Memory Chips (USB sticks, Flash memory)
• Punched Cards
• Barcodes
6. Stuart Cunningham - Computer Platforms - 2003
Computer Architecture
• What’s in the box?
CPU
Hard Disk
Drive
RAM
BIOS
Sound Card
Graphic Card
Ports
Floppy
Disk Drive
Power
Supply
7. Stuart Cunningham - Computer Platforms - 2003
Ports
• Physical interface or socket to connect a
device to a computer
• Interfaced to the computer’s motherboard
• Two main types of port:
– Serial
• Data is transferred in streams
• One bit after the other
– Parallel
• Data bits are transferred alongside each other in
waves (concurrently)
• Common ports
– USB (Universal Serial Bus)
– Serial (9-pin) & (15-pin ‘game’ port)
– Parallel (25-pin)
– SCSI (Small Computer Systems Interface)
8. Stuart Cunningham - Computer Platforms - 2003
Sound & Graphic Cards
• Interface directly onto the motherboard
• Graphics Card usually uses the AGP
(Accelerated Graphics Port)
– Provides basic and / or advanced graphics
capability
– Often have graphics co-processors
– On-board VRAM (Video RAM)
• Sound card uses a PCI (peripheral
Component Interconnect) slot
– Allows computer to output sound to speakers and
record sounds.
– Adds MIDI (Musical Instrument Digital Interface)
capability
9. Stuart Cunningham - Computer Platforms - 2003
Hard Disk Drives (HDD)
• Magnetic storage medium
• Uses rotating metal disks (platters)
• Use read and write ‘heads’ to store and
retrieve information
• Large storage capacity
Disk Platter
Spindle
Read/Write
Heads
10. Stuart Cunningham - Computer Platforms - 2003
Floppy Disk Drive (FDD)
– Magnetic storage medium
– Uses rotating single, thin magnetic
disk
– Requires a drive to read the disk,
which has the read/write heads
– Small storage capacity
• Typically 1.44 Mb (High Density 3.5”)
– Portable
– Cheap
11. Stuart Cunningham - Computer Platforms - 2003
Magnetic Disks
– How the disk works:
Sector
Cluster
Track
12. Stuart Cunningham - Computer Platforms - 2003
BIOS
• Basic Input Output System (BIOS)
• Provides the computer with basic
functionality
• Built-in software, no disk access
– Usually a ROM chip on the motherboard
• Common BIOS manufacturers
– Award, Compaq, HP
• Settings are saved to a CMOS chip,
powered by a battery
– CMOS = Complementary Metal Oxide
Semiconductor
13. Stuart Cunningham - Computer Platforms - 2003
Random Access Memory (RAM)
• Used to store instructions that are in current
use
• Two main types of RAM:
– Static RAM (SRAM)
• reliable
• does not need to be constantly refreshed
• fast
• expensive
– Dynamic RAM (DRAM)
• more common
• slower than SRAM
• cheap
• must be constantly refreshed
– Both volatile’ (contents lost when power is off)
14. Stuart Cunningham - Computer Platforms - 2003
Random Access Memory (RAM)
• Cache Memory
– Essentially RAM that the CPU can access
quickly
• Is physically close to the processor
– Usually always SRAM
• Therefore, small sizes are common compared
to size of RAM
– Two levels of cache memory
• Level 1 - Situated inside the processor
– Commonly 512 kb
• Level 2 - A separate RAM chip on the
motherboard or in expansion slot
– Commonly 1024 kb (1 Mb)
16. Stuart Cunningham - Computer Platforms - 2003
Central Processing Unit (CPU)
• CPU has three important parts:
– ALU (Arithmetic and Logic Unit)
– Control Unit
– Registers
High Speed Registers
ALU Control
Unit
CPU
17. Stuart Cunningham - Computer Platforms - 2003
Central Processing Unit (CPU)
• Arithmetic & Logic Unit
– Handles mathematical and logical functions
(numerical)
– Deals with non-numerical logic operations
• Control Unit
– Handles all low-level hardware operations
• Input & Output Devices and CPU
– Carries out instruction handling
• Fetch Execute Cycle
• Registers
– Storage areas within the CPU
– Accessible at high speed
– Anything for processing must be kept in a register
– Can also hold the address of a memory location
18. Stuart Cunningham - Computer Platforms - 2003
Buses
• A collection of wires which connects
together the internal components of
the computer
– Allows transfer of data
• Main types of bus:
– Data bus
• Carries actual data bits (information)
– Address bus
• Transfers locations where data should be sent
– Control bus
• Carries status information
19. Stuart Cunningham - Computer Platforms - 2003
Buses
• How buses fit into the computer
system
INPUT OUTPUT
CPU
MEMORY
ADDRESS BUS
DATA BUS
CONTROL BUS
20. Stuart Cunningham - Computer Platforms - 2003
Computer Architecture
• The Von Neumann Model
– 1903 - 1957
– Mathematician
– Quantum physicist
– Worked on ENIAC
• Electronic Numerical Integrator and Computer
• Major development in computer technology
– Responsible for developing the Fetch
Execute Cycle, and his namesake -
• ‘Von Neumann Model’
– The original computer geek?!
21. Stuart Cunningham - Computer Platforms - 2003
Week 2
• What we know now!
– Input, Output, Storage
• Devices
• Media
– HDD
– FDD
– How magnetic Disks work
– Computer Architecture
• BIOS
• Ports
• The CPU
– ALU
– Control unit
– Registers
• Buses
• Von-Neumann
