PROGLANG-DATATYPES

• Data type


  Defines a collection of data values and a set of predefined operations on those values
• Primitive data type


  Data types that are not defined in terms of other types
• Primitive data types


  • Numeric
  • Boolean
  • Character
• Integer


  The most common primitive numeric data type
• Floating-point data type


  Models real numbers, but the representations are only approximations of many real numbers
• Decimal data type


  Stores a fixed number of decimal digits, with the decimal point at a fixed position in value
• Boolean data type


  Has a range of values that has only two (2) elements, one for true and one for false
• Character data type


  Used to store only a single character
• Character string (or string) type

  Has values that consist of sequences of characters
• Common string operations


  • Assignment
  • Concatenation
  • Substring reference
  • Comparison
  • Pattern matching
• String length options


  • Static length string
  • Limited dynamic length string
  • Dynamic length string
• Ordinal type


  Consists of a range of possible values that can be easily associated with the set of positive integers
• User-defined ordinal types


  • Enumeration type
  • Subrange type
• Array


  A container object that stores a fixed number of values of a single type
• Categories of arrays


  • Static array
  • Fixed stack-dynamic array
  • Stack-dynamic array
  • Fixed-heap dynamic array
  • Heap-dynamic array
• Common array operations


  • Assignment
  • Concatenation
  • Comparison for equality and inequality
  • Slices
• Rectangular array


  A multidimensional array in which all of the rows and columns have the same number of elements
• Jagged array


  Consists of rows with different number of elements
• Slice


  Another array produced after extracting certain elements from an array
• Associative array


  An unordered collection of data elements that are indexed by an equal number of values called keys
• Record


  A collection of data elements in which the individual elements are identified by names and accessed through offsets from the beginning of the structure
• Tuple


  A data type that is similar to a record, except that the elements are not named
• List


  Represents an ordered sequence of values, which is usually not separated by any punctuation
• Union


  A type whose variables may store different type of values at different times during program execution
• Types of unions


  • Free unions
  • Discriminated unions
• Pointer type


  One in which the variables have a range of values that consists of memory addresses and a special value called nil
• Heap-dynamic variable


  Variables that are dynamically allocated form the heap
• Fundamental pointer operations


  • Assignment
  • Dereferencing
• Reference type


  A variable that refers to an object or a value in memory
• Type checking


  The activity of ensuring that the operands of an operator are of compatible types
• Coercion


  The process automatically converting an operator
• Type error


  The application of an operator to an operand of an inappropriate type
• Dynamic type checking


  Type checking at run time
• Strongly typed programming language


  One where type errors are always detected
• Type equivalence


  Two (2) types are equivalent if an operand of one (1) type in an expression is substituted for one of the other type, without coercion
• Approaches to defining type equivalence

  • Name type equivalence
  • Structure type equivalence