What’s in your iPad?


Computers perform the same basic function: inputting, outputting, processing, and storing data. Also, most computers have the same basic components: input, output, memory, data path, and control. In other words, a computer needs input devices, output devices, storage, and a processor to function.

Liquid Crystal Display (LCD) – A display technology using a thin layer of liquid polymers that can be used to transmit or block light according to whether a charge is applied

Active Matrix Display – A LCD using a transistor to control the transmission of light at each individual pixel

Pixel – the smallest individual picture element. Screens are composed of hundred of thousands to millions organized in a matrix.

While there are a variety of ways to implement a touch screen, many tablets today use capacitive sensing. Since people are electrical conductors, if an insulator like glass is covered with a transparent conductor, touching distorts the electrostatic field of the screen, which results in a change in capacitance or storage of electrical energy. This technology can allow multiple touches simultaneously.

Input/Output Devices:

  • LCD display
  • Camera
  • Microphone
  • Headphone jack
  • Speakers
  • Accelerometer
  • Gyroscope
  • Wi-Fi network
  • Bluetooth network

Input and output devices dominate space in a device while data path, control and memory makeup a tiny portion of space.

Integrated Circuits (chips) – A device with dozens to millions of transistors

Central Processing Unit (CPU or processor) – The active part of the computer, which contains the data path and control and which adds numbers, test numbers, signals I/O device to activate, and so on. Data path performs arithmetic operations while control tells the data path, memory, and I/O device what to do according to the instructions of the program

Volatile Memory (Main or primary) – storage for programs and data for programs during runtime

  • Dynamic Random Access (DRAM) – A volatile chip that provides random access to any location with an access time of 50 nanoseconds
  • Static Random Access (SRAM) – A volatile chip that is faster and less dense than DRAM
  • Cache – A volatile, small, fast memory that acts as a buffer for a slower, larger memory

Nonvolatile Memory (Secondary) – hold data and programs between

  • Magnetic Disks – Composed of rotating platters coated with a magnetic recording material. Access times are 5 ~ 20 milliseconds
  • Flash Memory – Slower and cheaper than DRAM, yet it’s more expensive per bit and more power efficient than disks. Access times are 5 ~ 50 microseconds

Multiple DRAM chips work together to contain the instruction and data of a program.

Abstraction : Hardware and the lowest-level software such instruction set architecture and application binary interface (ABI).

Networks Advantages:

  • Communication – Exchange of information between computers at high speeds
  • Resource Sharing – Computers on the same network share I/O devices
  • Nonlocal Access – Remote access to your computer

With the dramatic rise in deployment of networking and increase in capacity, network technology became an integral part to the information revolution.

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