Problem Solving and Program Design in C (5th Edition) by Jeri R. Hanly and Elliot B. Koffman

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Problem Solving and Program Design in C (5th
Edition)by Jeri R. Hanly and Elliot B. Koffman

• CP 202
• Chapter 6

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Pointer

• C uses pointers in three different ways
• C uses pointers to create dynamic data structures
  -- data structures built up from blocks of memory
  allocated from the heap at run-time.
• C uses pointers to handle variable parameters
  passed to functions.
• Pointers in C provide an alternative way to
  access information stored in arrays. Pointer
  techniques are especially valuable when you work
  with strings. There is an intimate link between
  arrays and pointers in C.

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PointerReference Operator ()

• The memory of your computer can be imagined as a
  succession of memory cells.
• As soon as we declare a variable, the amount of
  memory needed is assigned for it at a specific
  location in memory (its memory address).
• The address that locates a variable within memory
  is what we call a reference to that variable.
• reference to a variable can be obtained by
  preceding the identifier of a variable with an
  ampersand sign (), known as reference operator.
• The variable that stores the reference to another
  variable is what we call a pointer.

andy 25 fred andy ted andy

1. we have assigned the value 25 to andy (a variable
   whose address in memory is 1776).
2. copied to fred the content of variable andy.
3. copies to ted the reference of andy.

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PointerDereference Operator ()

• Using a pointer we can directly access the value
  stored in the variable which it points to. To do
  this, we simply have to precede the pointer's
  identifier with an asterisk (), which acts as
  dereference operator and that can be literally
  translated to "value pointed by".
• Notice the difference between the reference and
  dereference operators
• is the reference operator and can be read as
  "address of
• is the dereference operator and can be read as
  "value pointed by"

andy 25 ted andy beth ted
(andy) andy
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PointerDeclaring Variables of Pointer Types

• Due to the ability of a pointer to directly refer
  to the value that it points to, it becomes
  necessary to specify in its declaration which
  data type a pointer is going point to.
• Declarationsint number char character
  float greatnumber

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PointerExample 1

• // my first pointer
• include ltiostreamgt
• using namespace std
• int main ()
• int firstvalue, secondvalue
• int mypointer
• mypointer firstvalue
• mypointer 10
• mypointer secondvalue
• mypointer 20
• printf("firstvalue is d\n", firstvalue)
• printf("secondvalue is d\n", secondvalue)
• return 0

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PointerExample 1 (OUTPUT)

• // my first pointer
• include ltiostreamgt
• using namespace std
• int main ()
• int firstvalue, secondvalue
• int mypointer
• mypointer firstvalue
• mypointer 10
• mypointer secondvalue
• mypointer 20
• printf("firstvalue is d\n", firstvalue)
• printf("secondvalue is d\n", secondvalue)
• return 0

firstvalue is 10 secondvalue is 20
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Pointer (Example 2)Function with Output Arguments

• void /-this function returns 2
  results-/calculation(int num, / input
  / int cal1, / output / int cal2) /
  output / cal1 num num cal2 num
  numint main(void) int value / input
  number entered by user / int sum / output
  num num / int multi / output num num
  / printf(Enter a value to analyzegt
  ) scanf(lf, value) calculation(value,
  sum, multi) printf(Sum d, Different
  d, sum, multi) return(0)

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Pointer (Example 3)
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Pointer (Example 3)