Structures

• A record is a structured data type with a fixed number of components. The components may be accessed by name. The components may be heterogeneous.
• A field is a member of a record.
• Think of drivers license.
• Records in c/c++ are implemented as structs.
• Syntax:

  struct identifier {
      memberlist
  };
      

• And a member list is

• DataType identifier_list;
      

• struct StudentT {
      string firstName, 
             lastName;
      char   middleInitial;
  };
      

• Please note, this declares a type, it does not allocate memory.
• In some sense it provides a template, so the compiler knows how to build one of these.
• This should be done in the global declaration space at the top.
• It probably should be done before function prototypes, as you will probably want to use structs to pass parameters.
• Remember, int C++ everything must be declared before it is used (or at least partially declared, as we will see later).
• We declare instances of a struct just as we declare instances of any other type.

• int main() {
     float  GPA;
     StudentT theStudent;
     StudentT studentOne, 
              studentTwo;
      

• A member selector is an expression use to access components of a struct instance.
  • structInstance.fieldName
  • theStudent.firstName = "Dan";
  • cout &tl;< theStudent.lastName
• Operations on the entire structure are known as Aggregate Operations
• An Aggregate operation is an operation on an entire data structure, as opposed to an operation on an individual component.
• Aggregate operations supported on structures
  • NO IO cout << studentOne
  • Yes to assignment, studentOne = studentTwo
  • No (sort of) to Math, studentOne = studentTwo + theStudent
  • No to comparison if (studentOne == studentTwo)
  • Yes to pass as parameters
  • Yes to return values from functions.
• Structure data should be cohesive.