Friday, May 4, 2018
Programming Abstractions!
Spring 2018!
Stanford University !
Computer Science Department!
Lecturer: Chris Gregg!
reading:!
Programming Abstractions in C++, Chapter 11
CS 106B
Lecture 15: Dynamic
Memory Allocation
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Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
CS 106B Lecture 15: Dynamic Memory Allocation, Lecture notes of Operating Systems
Lecture notes from a CS 106B lecture at Stanford University. The lecture covers dynamic memory allocation in C++, including pointers, structs, the -> operator, and the new and delete keywords. The notes also include a mystery function example with output. The document could be useful as study notes or exam preparation for a computer science course covering C++ and memory allocation.
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Friday, May 4, 2018
Programming Abstractions Spring 2018 Stanford University Computer Science Department Lecturer: Chris Gregg reading: Programming Abstractions in C++, Chapter 11 CS 106B Lecture 15: Dynamic Memory Allocation
Today's Topics
- Logistics
- Question from a student: "Is there any other interesting youtube channel you can
recommend besides Numberphile?" Glad you asked! (see YouTube Video page at
the end of the slides)
- More on Pointers
- Mystery function
- Pointers and Structs
- The -> operator
- Dynamic Memory Allocation
- The new and delete keywords
- The "heap"
Introduction to Pointers
What is a pointer??
a memory address!
Mystery Function: What prints out? void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Mystery Function: What prints out? void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Answer: a 4 0x b 8 0xab c
0xf a
0x5e b //// /////// c
0x7c
Mystery Function: What prints out? void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Answer: a 4 0x b 8 0xab c
0xf a
0x5e b //// /////// c
0x7c
Mystery Function: What prints out? 4 8 - Answer: a 4 0x b 7 0xab c
0xf a
0x5e b //// /////// c
0x7c void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Mystery Function: What prints out? 4 8 - Answer: a 4 0x b 7 0xab c
0xf a
0x5e b //// /////// c
0x7c void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Mystery Function: What prints out? 4 8 - Answer: a 11 0x b 7 0xab c
0xf a
0x5e b //// /////// c
0x7c void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Mystery Function: What prints out? 4 8 - -2 11 7 Answer: a 11 0x b 7 0xab c
0xf a
0x5e b //// /////// c
0x7c void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Mystery Function: What prints out? 4 8 - -2 11 7 11 7 - Answer: a 11 0x b 7 0xab c
0xf a
0x5e b //// /////// c
0x7c void mystery(int a, int& b, int* c) { a++; (*c)--; b += *c; cout << a << " " << b << " " << *c << " " << endl; } int main() { int a = 4; int b = 8; int c = -3; cout << a << " " << b << " " << c << " " << endl; mystery(c, a, &b); cout << a << " " << b << " " << c << " " << endl; return 0; }
Pointers and Structs
- (^) Pointers can point to a struct or class instance as well as to a regular variable.
- (^) One way to do this would be to dereference and then use dot notation: date 0xa month 10 day 31 daysInMonth() toString() ... ... Date d; d.month = 7; Date dPtr = &d; cout << (dPtr).month << endl;** dPtr 0xa 0x7c
Pointers and Structs
- (^) So, we have a different, and more intuitive syntax, called the "arrow" syntax, -> : date 0xa month 10 day 31 daysInMonth() toString() ... ... Date d; d.month = 7; Date dPtr = &d; cout << dPtr->month << endl;*
- (^) We will use the arrow syntax almost exclusively when using structs. dPtr 0xa 0x7c
Pointers and Structs
- (^) The arrow syntax can be used to set a value or call a function in a struct via a pointer, as well: date 0xa month 10 day 31 daysInMonth() toString() ... ... Date d; d.month = 7; Date dPtr = &d; cout << dPtr->month << endl; p->day = 1; cout << p->day << endl; // 1 cout << p->toString() << endl; // 10/* dPtr 0xa 0x7c