quartz/content/notes/09-intro-to-c-2.md

title	aliases	tags
09-intro-to-c-2		cosc204

Variables and Pointers

va memory[3]
*va memory[memory[3]]
**va memory[memory[memory[3]]]

* is known as dereferncing ** is known as double-dereferncing

Names and places

names are allocated to emmory locations of declaration

&b; wherever in memory b is stored

Why Pointers

• abstractions
  • dont need to know which "object" to manipulate
• ability to change a parameter
• multiple return values from a routine
• efficiency
  • dont need to copy anything to pass a pointer

Call by value

• The value of the variable is passed to the called routine.
• changes to the parameter do not propogate to the caller

Call by address

• address of parameter is passed to the rountine
• changes do propogate back to the caller
• more efficient because we only need to pass a pointer and not a value

Multiple results

• c routine can return at most one value
• you can use input parameters which are pointers for "returning" results

Arrays

• strings
  • terminated by "\0"
• argc, argv[]
  • length specified
• null terminated
  • array of pointers

Pointer arithmetic

• ++ move a pointer fowards in an array
• -- move a pointer back in an array
• these operations are "type aware" and increment (the pointer) by the size of the elements of the array