Data Structures 605.202.91

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Data Structures 605.202.91

• Robert Holder
• Johns Hopkins University
• Applied Physics Laboratory
• robert.holder_at_jhuapl.edu

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Agenda

• Whats wrong with the way I program now??
• Modularity
• Abstraction
• Program design with abstraction

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Whats wrong with the way I program now??

• testing
• human comprehension
• reusability
• redundancy
• maintenance
• divide and conquer

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Modularity

• What is modularity?
• What are the benefits of modularity?

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What is modularity?

• describes a program organized into loosely
  coupled, highly cohesive modules
• -Carrano and Prichard, p. 7
• a technique that keeps the complexity of a large
  program manageable by systematically controlling
  the interaction of its components
  -Carrano and Prichard, p. 106

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What are the benefits of modularity? (These may
sound familiar)

• testing
• human comprehension
• reusability
• redundancy
• maintenance
• divide and conquer

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Abstraction

• what, NOT how
• procedural abstraction
• data abstraction

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Abstraction

• what
• method lookup() accepts a name and returns a
  phone number
• how
• method lookup() accepts a name to use as a key to
  find the corresponding personnel record in a
  hashtable, and returns the stored phone number

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Abstraction

• procedural abstraction
• method lookup() accepts a name and returns a
  phone number
• data abstraction
• given a set of personnel records, a user may add
  a record, delete a record, or lookup a phone
  number

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Abstraction
data abstraction
abstract data type (ADT)
add()
delete()
data structure
name
lookup()
phone number
procedural abstraction
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Program design with abstraction

• specification
• implementation

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Specification

• what information do you have?
• what operations can be performed on that data?
  (data abstraction)
• what will the interface be for those operations?
  (procedural abstraction)

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Implementation

• how will the information be represented? (data
  structure)
• implement operations
• information hiding