CP1300 C++ Pointers

• Pointer variables
  • Nothing useful yet, just the idea
  • Pointers to primitive types
    • Declaring pointer variables
    • Setting the pointer
    • Accessing and changing the contents pointed to
    • Assigning pointers to pointers
    • PrimitivePointers.cpp - program demonstrating pointers to primitive types
    • The null pointer
    • NullPointer.cpp - program demonstrating a null pointer
  • Pointers to structs
    • Setting the pointer
    • Accessing the struct
    • Accessing the fields
    • StructPointers.cpp - program demonstrating pointers to structs
    • Pointer fields
    • StructPointerFields.cpp - program demonstrating pointer fields in structs
    • Pointers inside structs (oooh, look, linked structures)
  • Arrays and pointers
    • Array of pointers
    • ElementPoints.cpp - program demonstrating use of an array of pointers
    • Pointers into arrays are arrays
    • ArrayPointer.cpp - program using a pointer as an array name

• Dynamic memory allocation
  • Creating new simple types
  • DynamicPrimitives.cpp - program demonstrating the creation of new primitive types
  • Creating new arrays
  • DynamicArrays.cpp - program demonstrating the creation of new arrays

• Pointers to objects
  • Pointers to existing objects
  • Accessing methods
  • SimpleClass.h, SimpleClass.cpp, UseSimpleClass.cpp - program demonstrating pointers to objects
  • Creating new objects
  • SimpleClass.h, SimpleClass.cpp, UseNewSimpleClass.cpp - program demonstrating creation of new objects
  • Pointers inside objects (ooh, look, linked object structure)

• Pointers as parameters
  • Pass by value (= pass the referred object by reference)
  • PassByValue.cpp - program demonstrating passing pointers by value
  • Pass by reference
  • PassByReference.cpp - program demonstrating passing pointers by reference

• Simple pointers

Tutorial Questions

• Linked structs

Exam style questions

1. Write a declaration for a variable that points at a char.
2. What is the output from this code?

   int anInt;
   int *intP1;
   int *intP2;
   
   intP1 = &anInt;
   *intP1 = 27;
   anInt = 27;
   intP2 = new int;
   *intP2 = 16;
   intP1 = intP2;
   *intP1 = 27;
   
   cout << anInt << " " << *intP1 << " " << *intP2 << endl;
        

3. Write a code segment that declares an array of 10 pointers to int, initializes all of them to point at the int variable anInt, and finally prints out the contents of anInt using the 5th array element.
4. What is the output from the following code?

   char name[12];
   char *offset;
   
   strcpy(name,"Sutcliffe");
   offset = &name[4];
   cout << offset << endl;
        

5. Write a code segment that declares a pointer to a float, and then makes the pointer be the "name" of a newly created array of 10 floats.
6. If FredsClass is a class that has only a default constructor, write a code segment that declares a pointer to a FredsClass object, and creates a new object pointed to by the variable.
7. What is the output from the following program?

   //-----------------------------------------------------------------------------
   #include 
   
   typedef int *intPointer;
   
   void makeANewInt(intPointer intP1,intPointer &intP2);
   //-----------------------------------------------------------------------------
   int main(void) {
   
   int anInt;
   intPointer pointAtInt;
   
   anInt = 27;
   pointAtInt = &anInt;
   makeANewInt(pointAtInt,pointAtInt);
   cout << *pointAtInt << endl;
   
   return(0);
   }
   //-----------------------------------------------------------------------------
   void makeANewInt(intPointer intP1,intPointer &intP2) {
   
   intP2 = new int;
   *intP2 = *intP1 *2;
   
   }
   //-----------------------------------------------------------------------------