Microphone

• The diaphragm (2) is moved by the air molecule (1)
• That makes the coil (4) to create varying electric current depends on the loudness of sound
• Analog signal out (5)

Analog sound signal

Digital sound

Sampling rate

(Number of Steps in time)

Application of Mic

• Recording sound
• Speech recognition
• ...

Telephone banking

QR Code

Think Pair Share

1. Try to list applications of QR Code in your notebook

QR Code

• Quick Response Code
• Store a very large amount of data compare to usual barcode
  • Up to 7000 numbers / 1000 characters vs 30 numbers
• Able to have error detection and recovery, small damage on the code can still be scanned

Think Pair Share

1. Give 2 advantages and 1 disadvantages of QR Code compare to Barcode [3], write in notebook. 

Monitors

• Most common type of output device
• Major types of flat-panel monitors:
  • LCD
  • LED
  • OLED

Color components in a monitor:

LCD/LED Screen

• The orientation of liquid crystal can be controlled by electricity
• Thus affects the back light to pass through or not
• Light will be filtered by the color filter to display individual color

• LCD uses CCFL (fluorescent) as back light, while LED is using LED as light

Research

• What are the benefits of LED backlight (LED Monitor) compare to CCFL backlight (LCD Monitor)?
• What is the difference between LED and OLED display?
• Which type of screen panel is suitable for smartphones? Why?

Projector

• LCD Projector
  • LCD screen is illuminated by a powerful backlight
• DLP Projector
  • Micro mirrors to deflect the light from the screen or to the screen

Printers / Cutters

• Inkjet printer
• Laser printer
• 3D Printer
• 2D and 3D Cutters 

Inkjet printer

• A moving print head sprays ink droplets on to the paper from a cartridge filled with liquid ink

Laser printer

• The rotating printing drum is given a positive charge.
• A laser removes the positive charge from certain areas of the drum as it scans across it, creating a negatively charged copy of the text/image to be printed.
• On an ink roller, the toner is given a positive charge which attracts it to only the negatively charged areas on the printing drum.
• The toner then transfers from the negatively charged areas of the drum to some positively charged paper. 

https://www.youtube.com/watch?v=_UOU5_4fnzs

3D Printers

• Create 3-dimensional object from a computer model
• Usually a computer model is created by CAD (Computer aided design) software or from 3D Scanner
• Usually refers to Additive manufacturing
• 3D objects are created by layering a material, layer by layer

2D/3D Cutter

• Computer controlled the cutting tool to cut on the stock material
• It refers as subtractive manufacturing
• Examples of 2D cutter:
  • Laser cutter
  • Waterjet
• Examples of 3D cutter:
  • CNC (Computer numeric control) Mill / Router

Compare 3D Print / 3D Cutter

Early computers

• Difference Engine - Charles Babbage
  https://www.youtube.com/watch?v=BlbQsKpq3Ak
• Machine is purposely built, only able to perform certain tasks
• ENIAC - First general purpose computer
  https://www.youtube.com/watch?v=bGk9W65vXNA
• Allows reprogram (through hardware) the computer for different tasks

Von Neumann architecture

• Stored-program computer - not only data is stored in memory, but also instructions
• Modern computer stores instructions as well as data in RAM
• Benefits of Von Neumann architecture:
  •  

Main components in the architecture

• CPU (Central processing unit) contains:
  • Arithmetic Logic Unit (ALU) - Logical comparisons and calculations
  • Control Unit (CU) - controls flow of data and different components in CPU
  • Registers - Internal memory within CPU. Holds data and instructions during processing
• Buses - Connecting components for exchange of information. There are:
  • Control bus
  • Address bus
  • Data bus

Examples of Registers

• Program counter
• Instruction register
• Address register
• Accumulator

Fetch-Execution cycle

• Tryout: Little Man Computer
• Processor fetch one instruction by one
• Execute the instruction after decoding it
• Refer to p.49 in textbook for detail (note you don't need to memorize the whole process)

High-level and Low-level (programming) languages

Machine code

• The code that is directly understand by CPU
• Represented in binary numbers

Assembly language

• Low level programming language
• Machine specific - only CPU of the same architecture can use
• Can directly translate into Machine code, for CPU to run - using translator

Assembly

Machine code

High-level languages

• More human readable codes
• Allows programmers to focus on solving problems
• Usually not platform specific - the program code can be used in many different models of computer
• Some examples (from lowest level to highest)
  • C
  • C++
  • Java
  • Python
  • Javascript

Translators

• CPU can only understands machine code, therefore translators is needed to translate from programming languages
• Examples are:
  • Assemblers: for assembly languages
  • Compilers
  • Intrepreters 

Assemblers

• To translate assembly language into machine code
• Translation is more or less one-to-one mapping
• i.e. One line of assembly code became one single machine code instruction

Compilers

• Translate higher level languages to machine code
• Compiler will read the whole program, translate into machine code, and save as executable file
• Any syntax error in the code will stops the compilation and error message will display for the programmer to fix
• Examples of languages that needs compiler:
  • C++
  • Java

Interpreters

• Directly reads the code written in high level languages and instruct the computer to run
• Read and execute code one by one
• Will not store machine code
• Syntax errors usually not found until that line of code is executed
• Intrepreter must be installed to run such programs
• Usually refer as script languages, for example:
  • Python
  • Javascript

Main Memory

Memory unit (RAM)

• Made up of partitions
• Each partition has it's own address and contains content
• Usually each partition is 8 bit in content (1 byte)

• How many bits in each memory partition (content)?
• 8
• How many bits in each memory address?
• 32
• What is the maximum size of a 32 bit address? Show your working.

Study the memory illustration of a certain computer:

RAM: Random Access Memory

ROM: Read Only Memory

Firmware: ROM that holds programs to run on embedded computer

Bootstrap: ROM that contains startup instruction for computer

EPROM: Erasable Programmable ROM

Flashing: the process of erasing and rewriting data to ROM

RAM

• Random access memory
• Allows read and write of the content
• Volatile, temporary (working) memory for modern computer
• If RAM is full, modern Operating System will move data to HDD or other secondary storage devices
  • thus only keep those running program in RAM
  • too many running program will be v. slow
• Examples of RAM are DRAM and SRAM

Types of data access

• Sequential access
• Random Access / Direct access

from: wikipedia

ROM

• Read Only Memory
• Non-volatile / permanent memory
• Often store startup instructions for the computer:
  • Firmware: for embedded computer system
  • Bootstrap: for general purpose computers
    • Basic Input Output System (BIOS)
    • UEFI - replace BIOS and often found in recent PCs

BIOS (left) and UEFI 

EPROM

• Some types of ROM can be changed, one of them is EPROM (Erasable programmable read only memory)
  • Firmware of devices might need upgrade, e.g. Router
  • BIOS is also upgradable
• The act to modify EPROM is called flashing

Compare RAM and ROM

Secondary Storage

• Non-volatile
• Usually holds large amount of data (compare to main memory)
• Three main types (technology):
  • Magnetic
  • Optical
  • Solid-state

Punch card - one of the earliest storage media

Magnetic storage devices

• Read and write data by using electromagnets and magnetic fields to control tiny magnetic dots of data
• Represents 0 or 1 with the polarity of magnetic field
• Hard disk drive (HDD) stores data on the magnetic disk
  • Most common type of magnetic device
  • Cheap and fast enough
• Magnetic tape
  • Sequential access, very large in capacity
  • Great for backup large amount of data

Optical storage

• Optical disc are plastic disks with small pits on it
• Data is read by shining laser beam onto the surface and detect whether it is pit or bump (thus 1 or 0)
• Writing data required burning the pit on the surface with higher laser power
• DVD-RAM / DVD-RW are rewritable type of optical storage media

Comparison of Optical Disc

Solid state

• Solid state storage devices store data electronically (e.g. Flash memory, EEPROM)
• Unlike magnetic / optical, it involved no mechanical moving parts when read/write
• Access speed (time to locate required data) is much faster than mechanical media and also data transfer speed
• Examples are: SSD, Flash memory Drive (USB drive), Flash Memory (SD Card etc.)

HDD (mechanical) vs SSD

Create a mind map about storage devices

Calculate storage requirements of a file

Storage unit and conversion

Note: the short form for byte is B while short form for bit is b

Note 2: Storage usually measured in byte, while transfer speed usually in bit per second (bps)

Class exercise

Calculate the storage requirements for the following cases:

1. A plain text file containing the following text:
   This is a text file.
2. A 16x16 black-and-white image
3. A 16x16 Grayscale (8-bit) image
4. Uncompressed 2 hour HD
   (1280x720) movie

Revision Questions