Pointers and memory Ch 9 & 13.1 Highlights - new & delete - PowerPoint PPT Presentation

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Pointers and memory Ch 9 & 13.1 Highlights - new & delete Pointers A pointer is used to store a memory address and denoted by a * (star!) Here variable xp is a integer pointer The * goes from address to variable (much like when you

Pointers and memory Ch 9 & 13.1
Highlights - new & delete
Pointers A pointer is used to store a memory address and denoted by a * (star!) Here variable xp is a integer pointer The * goes from address to variable (much like when you hit ENTER on a url) (See last time: pointerBasics.cpp)
Boxes What is comes next in this pattern? Basic programming: Ask for one box with a name Intermediate programming: Ask for multiple boxes with one name Advanced programming: ??? ???
Boxes What is comes next in this pattern? Basic programming: Ask for one box with a name Intermediate programming: Ask for multiple boxes with one name Advanced programming: Ask for a box without giving it a name
new Pointers are also especially useful to use with the new command The new command will create a variable (box) of the type you want ask for box The new integer has no separate name, just part of xp (as array boxes part of array name) (See: newMemory.cpp)
new What does this do?
new What does this do? Asking for a lot of boxes there... (See: memoryLeak.cpp)
delete When your program exits, the operating system will clean up your memory If you want to clean up your memory while the program is running, use delete command (See: deleteMemory.cpp)
delete As you can manage how you want to create new variables/boxes, using new/delete is called dynamic memory Before, the computer took care of memory by creating variables/boxes when you use a type then deleting when the function ends Before Now
delete This is also a memory leak: By the 3 rd line, there is no link back to the box on the 2 nd line (dangling pointer) There should be a “delete” for every “new”
delete Memory management is a hard part of C++ You need to ensure you delete all your boxes after you are done with them, but before the pointer falls out of scope (see: lostPointer.cpp) Some other languages manage memory for you
Person class The ability to have non-named boxes allows you to more easily initialize pointers (See: personV3.cpp)
Pointer to pointer You can have multiple stars next to types: Each star indicates how many arrows you need to follow before you find the variable int*** int** int* int 8 x (See: pointerPointers.cpp)

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