Methods to manipulate a collection of values under one name.

1
Arrays and Structures

• Methods to manipulate a collection of values
  under one name.
• Arrays
• Homogenous data
• Variable quantity of data items all of the same
  type
• Structures
• Heterogeneous data
• Fixed quantity of data values of different types

2
Arrays

• Declaration
• ltdata-typegt ltvar-namegtint-qty
• Access
• ltvar-namegtsubscript
• Subscript
• Integer
• In the range 0 to n-1, where n is the number of
  elements

3
Structures

• Definition
• struct ltstruct-namegt // typically in global area
• ltelementsgt. / composed of data types and
  element names /
• Declaration
• ltstruct-namegt ltvar-namegt
• Access
• ltvar-namegt.ltelement-expressiongt

4
Array Examples

• int counts100 counts0 0
• double speeds2000 speeds1999 1.23
• string names500 cout ltlt Name ltlt
  names10

5
Structures Example

• Structures
• struct employee
• string name
• float annual_salary
• int dept_num
• employee boss
• boss.name Bill
• cout ltlt Annual Salary is ltlt boss.annual_salary
  ltlt \n

6
Nesting

• An array may be an array of arrays or an array of
  structures.
• A structure may have arrays as members or other
  structures as members.
• These arrays or structures may also have arrays
  or structures as members, and so forth to any
  arbitrary depth.

7
Nesting Example

• struct class
• string time
• string place
• string students30 // structure w/ array
• class schedule5 // array of structures
• schedule0.place Robinson 310
• schedule0.students0 Bill

8
Arrays and For Loops

• For loops are typically used to process arrays.
• Typically when using arrays, the number of
  elements that actually contain valid data is
  saved in a variable.
• for (i0 iltNUM_ELEMENTS i)
• countsi 0
• for (i0 iltn i)
• areai basei heighti

9
Sentinals

• int SENTINEL -1
• Sentinels may also be used
• i 0
• while (speedsi ! SENTINEL)
• cout ltlt speedi ltlt \n
• i

10
Terminology

• Scalars a single data value
• Vectors a one-dimensional array
• Matrices a two-dimensional array

11
Strings

• A string is a array of characters.
• A string literal is delimited by double-quotation
  marks.
• Examples
• Computer
• special characters in it !_at_\\\
• one
• 1
• NOT strings a, 1, 1, one

12
Another method to do input

• getline(cin, a_string, \n)
• This will accept all input up to a newline
  character. It will store the input (NOT the
  newline) in a_string.
• There are functions to do character-at-a-time
  input, as well as other special input functions
  (see lecture on streams and files).
• In practice, these functions sometimes do not mix
  well with cin, with erratic results.

13
Using Strings in C

• include ltstringgt
• Declaring strings
• string name
• string account_number
• Using strings
• Name Bob
• cin gtgt account_number
• whole_name last_name , first_name //
  Concatenation
• Name_length name.length()

14
Pointers

• A pointer is a variable that contains the address
  of another variable, that is, a memory address.
• Definition ltdata-typegt ltvar-namegt
• Access ltvar-namegt for the pointer itself
  ltvar-namegt for the variable pointed to
  (de-referencing).

15
Dynamic Memory

• Three areas of memory
• Global defined outside any function (allocated
  once)
• Local defined inside a function (allocated on
  the system stack)
• Dynamic (also known as the heap)
• Accessed through operators new and delete
• To request a section of memory
• ltpntr-vargt new ltdata-typegt
• To access that memory use operators , , -gt
• To return that memory delete ltpntr-vargt

16
Memory Examples

• include ltiostreamgt
• using namespace std
• int g // global visible from here to end of
  file
• void main()
• float l // local visible from here to end of
  block
• double h new double // heap allocation
• delete h // heap de-allocation
• int weights new intnum_weights // delete

17
Reading

• Chapter 9
• Chapter 11, Section 1-2
• Chapter 13, Sections 1-2