CMSC104

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Lecture 24: Separate Compilation and Pointers

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Reading Assigned: 6.1-6.2 and 8.5

Homework Due:  Homework 11

Homework Assigned:  Homework 12

Classwork Assigned:  Classwork 13

Topics Covered:

• Homework 11 questions?
• Upcoming Homework 12 questions?
• Quiz 4 - Results
• Reminder about how final grade is calculated
• Go back and finish separate compilation
• Pointers (aka How to Get Multiple Values Back from Functions)
  • Remember variables are stored at a defined location in memory
  • Normally when we pass arguments to functions, the computer allocates a new memory region
  • To get a value back from a function, we used to have to set a variable equal to the return value
  • Pointers allow us to pass a pointer to the memory location of a variable to a function
  • The function can then modify the same memory location occupied by the original variable
  • Pointers are one of the more complicated parts of C, so it will take a while to "get it"
• Pointer syntax
  • A normal integer variable "int x;"
  • A pointer to an integer "int *y;"
  • Getting the address of a normal variable "&x"
  • Setting a integer pointer to point to an integer: "int *y = &x;"
  • A program example
  • A program using pointers to pass back a value
• Operators used with pointers
  • * - dereference operator
  • & - address of operator