Many students find it difficult understanding the concept of Object Oriented Programming OOP

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• Many students find it difficult understanding
  the concept of Object Oriented Programming (OOP)
• Lack of exciting labs leads to a loss of
  interest
• Created with partial support from the National
  Science Foundations Division of Undergraduate
  Education through CCD grant DUE 97-52626 and ILI
  grant DUE 98-50983.
• MIPPET has 4 switches, 4 LED's, a High Current
  Output, an A/D converter and two communication
  ports

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• Object Class provides a high level coding
  structure for the user

Mippet (int port) //
Precondition Mippet must be connected to
parallel port at //
address "port" (can be 0x378, 0x278 or 0x3BC)
// Postcondition Mippet is initialized to
all items off // (status
port bits 0-3 low, 4-7 high) void
ReadSwitches (bool switch0, bool switch1,
bool switch2, bool switch3)
// Precondition None //
Postcondition Sets the switch parameters to 0 or
1 depending on //
whether the switch is pressed or not at the
instant // the function
call is made (0 not pressed, //
1 pressed) // Returns None
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• MIPPET connects to the parallel port of a
  computer
• All inputs and outputs are through pins on the
  parallel port
• To use a port, we need to know its base address
  and the semantics of its usage provided by the
  data sheet

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• MS C/C provides two functions to write/read
  from the port inp outp
• e.g. The parallel port has a base address of
  0x378.
• To read the Status Port (located at the
  base
• address1)
• int x
• x inp(0x379)
• To set or clear a bit, need to create a mask

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• Say we want to set Logical Output 3 high.
• We know that Logical Output 3 is connected to
  pin 4, which is bit 2 on the status port
• Since we want to modify bit 2, our mask will be
  0000 0100 0x04
• But we cannot just write 0x04 (0000 0100) to
  the port as this will clear all other bits.

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• Must read in the existing value of the data
  port
• e.g. x inp(0x378)
• We take this value and OR it with our mask
  (0x04)
• ORing this mask with the value read from the
  status port sets bit 2 and keeps all other values
  unchanged.
• e.g. x 1100010 1100110
• OR 0000100 0000100
• -----------
  -----------
• 1100110 1100110

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• Talking to devices is basically a matter of
  reading/writing to ports
• Abstraction is a wonderful thing!
• Hiding
• Device changes, client does not notice

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QUESTIONS?