CS139 - Abstract Concepts

Value

• Note difference between the value and how a value is communicated
• A value is an abstraction
• Examples of simple values: one, 52, XII, red, truth, the character 'p'
• Example of complex value: a checking account entry (date, check#, amount, recipient, etc)
• For complex values, maybe "state" is a better word

Data Type

• A set of values
• Examples: integers, rational numbers, colors, boolean, characters

Primitives and Objects

• For now, we will think of them as the same thing
• A "container" for a value
• Store a single value of a particular data type (but that value may be "complex")
• Has a "name"
• Creating a "container" is called "instantiation" or declaration.

Variables, contants, literals

• Different kinds of "containers":
  • Literals: store explicit values: 1, 'a', true
  • Constants: store unchanging values that represent some concept: MAX_SAT_SCORE, GPA_FOR_A, INCHES_PER_FOOT
  • Variables: store values that can change

Identifiers/Names

• Naming conventions:
  • titlecase: ThisIsTitleCase
  • mixedcase: thisIsMixedCase
  • uppercase: THIS_IS_UPPERCASE
  • lowercase: thisislowercase
  • lowercase hyphenated: this-is-lowercase-hypenated

Operations/Functions and Methods

• Examples: addition, !=, >, &&
• Function concept in math
• Range and domain
• Zero or more "operands"
• Operands and result may not all be the same data type
• Side effects
• Assignment

Abstract Data Type

• A data type and the operations for that data type

Type Conversion

• Implicit or explicit
• Example: 2 / 1.4

Input/Output

• Queues (sequential), also known as "streams"
• No knowledge of prior or future input
• Interface with world outside the program
• out, in, err
• Mapped to file or device by operating system

Date: 09/04/2005