This document discusses data structures and abstract data types. It covers one-dimensional and multidimensional arrays in C++. Arrays allow storing a collection of elements of the same type that can be accessed via an index. The document provides examples of declaring, initializing, accessing, and passing arrays. It also discusses how arrays are stored contiguously in memory. Functions are demonstrated that take arrays as arguments to operate on the elements. Multidimensional arrays generalize this to multiple indices.

1. 1
Data Structures and Abstract
Data Types
Chapter 2

2. 2
Chapter Contents
1 Data Structures, Abstract Data Types and
Implementations
2 Static Arrays
3 Multidimensional Arrays (optional)
4 Dynamic Arrays
5 C-Style Structs (optional)
6 Procedural Programming

3. 3
Chapter Objectives
• Look at ADTs, implementations in detail
• Introduce arrays as ADTs
• See arrays implemented as C++ static arrays
• (Optional) Describe multidimensional arrays
• Extend pointers to use in dynamic arrays
• (Optional) Show use of C++ structs to model
objects with multiple attributes
• Show example of procedural programming
paradigm

4. 4
Data Structures, Abstract Data
Types, and Implementations
• Consider example of an airplane flight with
10 seats to be assigned
• Tasks
– List available seats
– Reserve a seat
• How to store, access data?
– 10 individual variables
– An array of variables

5. 5
Data Structures, Abstract Data
Types, and Implementations
• Implementation consists of
– Storage (data) structures
– Algorithms for basic operations
• Note following figure
– C++ provides large collection of data types and
structures

6. 6
C++ Data TypesC++ Data Types
structured
array struct union class
address
pointer reference
simple
integral enum
char short int long bool
floating
float double long double

7. Structured Data Type
7
A structured data type is a type that
– Stores a collection of individual
components with one variable name
– And allows individual components
to be stored and retrieved by their
position within the collection

8. 8
Arrays
• Collection of data elements
– All of same type
– Each accessed by specifying position
• Static array
– Compiler determines how memory allocated
• Dynamic array
– Allocation takes place at run time

9. 9
Single Dimension Arrays
• Syntax:
ElementType arrayName [CAPACITY];
ElementType arrayName [CAPACITY] =
{ initializer_list };
• Example:
int b [10];
• Elements accessed by
– name and [ ] operation b[5]

10. 10
Character Arrays
• Elements of an array may be of any type
– Including characters
• Example:
char name [NAME_CAPACITY] =
"John Doe";
• If array initialized shorter than specs
– extra locations filled with null character

11. 11
Subscript Operation
• We have said elements
accessed by name and [ ]
numList[5]
• Consider the [ ] to be an
operator
– The subscript operator
– Performs address
translation
• Name of the array is a
pointer constant
– The base address

12. Declare variables to
store and total 3 blood pressures
12
int bp1, bp2, bp3;
int total;
40024000 4004
bp2bp1 bp3
cin >> bp1 >> bp2 >> bp3;
total = bp1 + bp2 + bp3;

13. What if you wanted to store and
total 1000 blood pressures?
13
int bp[1000];
// Declares an array of 1000 int values
bp[0] bp[1] bp[2] . . . . bp[999]
5000 5002 5004 5006
. . . .

14. One-Dimensional Array
Definition
14
An array is a structured collection of components
(called array elements), all of the same data type,
given a single name, and stored in adjacent
memory locations
The individual components are accessed by using
the array name together with an integral valued
index in square brackets
The index indicates the position of the component
within the collection

15. Another Example
15
• Declare an array called temps which will
hold up to 5 individual float values
float temps[5]; // Declaration allocates memory
temps[0] temps[1] temps[2] temps[3] temps[4]
7000 7004 7008 7012 7016
number of elements in the array
indexes or subscripts
Base Address

16. Declaration of an Array
16
• The index is also called the subscript
• In C++, the first array element always has
subscript 0, the second array element has
subscript 1, etc.
• The base address of an array is its
beginning address in memory
SYNTAX
DataType ArrayName[ConstIntExpression];

17. Yet Another Example
17
• Declare an array called name which will hold
up to 10 individual char values
char name[10]; // Declaration allocates memory
number of elements in the array
name[0] name[1] name[2] name[3] name[4] . . . . . name[9]
6000 6001 6002 6003 6004 6005 6006 6007 6008 6009
Base Address

18. Assigning Values to
Individual Array Elements
18
float temps[5]; int m = 4; // Allocates memory
temps[2] = 98.6;
temps[3] = 101.2;
temps[0] = 99.4;
temps[m] = temps[3] / 2.0;
temps[1] = temps[3] - 1.2;
// What value is assigned?
temps[0] temps[1] temps[2] temps[3] temps[4]
7000 7004 7008 7012 7016
99.4 ? 98.6 101.2 50.6

19. What values are assigned?
19
float temps[5]; // Allocates memory
int m;
for (m = 0; m < 5; m++)
{
temps[m] = 100.0 + m * 0.2 ;
}
temps[0] temps[1] temps[2] temps[3] temps[4]
7000 7004 7008 7012 7016
? ? ? ? ?

20. Now what values are printed?
20
float temps[5]; // Allocates memory
Int m;
. . . . .
for (m = 4; m >= 0; m--)
{
cout << temps[m] << endl;
}
temps[0] temps[1] temps[2] temps[3] temps[4]
7000 7004 7008 7012 7016
100.0 100.2 100.4 100.6 100.8

21. Variable Subscripts
21
float temps[5]; // Allocates memory
int m = 3;
. . . . . .
What is temps[m + 1] ?
What is temps[m] + 1 ?
temps[0] temps[1] temps[2] temps[3] temps[4]
7000 7004 7008 7012 7016
100.0 100.2 100.4 100.6 100.8

22. A Closer Look at the Compiler
22
float temps[5]; // Allocates memory
To the compiler, the value of the identifier temps is
the base address of the array
We say temps is a pointer (because its value is an
address); it “points” to a memory location
temps[0] temps[1] temps[2] temps[3] temps[4]
7000 7004 7008 7012 7016
100.0 100.2 100.4 100.6 100.8

23. Initializing in a Declaration
23
int ages[5] ={ 40, 13, 20, 19, 36 };
for (int m = 0; m < 5; m++)
{
cout << ages[m];
}
ages[0] ages[1] ages[2] ages[3] ages[4]
6000 6002 6004 6006 6008
40 13 20 19 36

24. Passing Arrays as Arguments
24
• In C++, arrays are always
passed by reference
• Whenever an array is passed as
an argument, its base address is
sent to the called function

25. In C++,
No Aggregate Array Operations
25
• The only thing you can do with an
entire array as a whole (aggregate)
is to pass it as an argument to a
function
• Exception: aggregate I/O is
permitted for C strings (special
kinds of char arrays)

26. Using Arrays as
Arguments to Functions
26
Generally, functions that work with
arrays require 2 items of information
– The beginning memory address of the
array (base address)
– The number of elements to process in the
array

27. Example with Array Parameters
27
#include <iomanip>
#include <iostream>
void Obtain (int[], int); // Prototypes here
void FindWarmest (const int[], int , int&);
void FindAverage (const int[], int , int&);
void Print (const int[], int);
using namespace std;
int main ( )
{
// Array to hold up to 31 temperatures
int temp[31]
int numDays;
int average;
int hottest;
int m;
27

28. Example continued
28
cout << “How many daily temperatures? ”;
cin >> numDays;
Obtain(temp, numDays);
// Call passes value of numDays and address temp
cout << numDays << “ temperatures“ << endl;
Print (temp, numDays);
FindAverage (temp, numDays, average);
FindWarmest (temp, numDays, hottest);
cout << endl << “Average was: “ << average
<< endl;
cout << “Highest was: “ << hottest << endl;
return 0;
}
28

29. Memory Allocated for Array
29
temp[0] temp[1] temp[2] temp[3] temp[4] . . . . . temp[30]
6000
Base Address
50 65 70 62 68 . . . . . .
int temp[31];// Array to hold up to 31 temperatures

30. 30
void Obtain ( /* out */ int temp[] ,
/* in */ int number )
// User enters number temperatures at keyboard
// Precondition:
// number is assigned && number > 0
// Postcondition:
// temp[0 . . number -1] are assigned
{
int m;
for (m = 0; m < number; m++)
{
cout << “Enter a temperature : “;
cin >> temp[m];
}
} 30

31. 31
void Print ( /* in */ const int temp[],
/* in */ int number )
// Prints number temperature values to screen
// Precondition:
// number is assigned && number > 0
// temp[0 . . number -1] are assigned
// Postcondition:
// temp[0 . . number -1] printed 5 per line
{
int m;
cout << “You entered: “;
for (m = 0; m < number; m++)
{
if (m % 5 == 0)
cout << endl;
cout << setw(7) << temp[m];
}
}
31

32. 32
Using Arrays
• Accessing array for output
– See Fig. 1
• Accessing array for input from keyboard
– See Fig. 2
• Note use of arrays as parameters
– Must specify number of elements of array being
used

33. Figure1:Array Output
Function
void display(int theArray[], int numValues)
/*-----------------------------------------------------------------
Display values in an array of integers. Precondition: 0 <=
numValues < capacity of theArray. Postcondition: The
first numValues integers stored in theArray have been
output to cout.
-------------------------------------------------------------------------*/
{
for (int i = 0; i < numValues; i++)
cout « theArray[i] « 00 " .
cout « endl;
} 33

34. Figure 2: Array Input Function
#include <cassert>
void read(IntArray theArray, int capacity, int numValues)
/*-------------------------------------------------------------------------
Input values into an array of integers from the keyboard.
Preconditions: 0 <= numValues < capacity, which is the capacity
of theArray. Postcondition: numValues integers entered from the
keyboard have been stored in the first NumValues positions of
theArray
-------------------------------------------------------------------------/*
{
assert (numValues >= 0 && numValues <= capacity);
for (int i = 0; i < numValues; i++)
cin » theArray[i] ;
}
34

35. 35
#include <iostream>
using namespace std;
void main()
{
int Nums[4];
int Sum=0;
cout<<"Enter 4 Numbers :n";
for(int i=0;i<4;i++)
cin>>Nums[i];
for(int j=0;j<4;j++)
Sum+=Nums[j];
cout<<"Sum = "<<Sum<<endl;
}

36. 36
Multidimensional Arrays
• Consider multiple pages of the student grade
book
const int NUM_ROWS = 10, NUM_COLS = 5,
NUM_RANKS = 10;
typedef double
ThreeDimArray[NUM_ROWS][NUM_COLS][NUM_RANKS];
. . .

37. Example on Multidimensional Arrays
• #include <iostream> using namespace std;
• int main()
• {
• // A 2-Dimensional array
• double distance[2][4] = {44.14, 720.52, 96.08, 468.78, 6.28, 68.04, 364.55, 6234.12};
• // Scan the array from the 3rd to the 7th member
• cout << "Members of the array";
• cout << "nDistance [0][0]" << ": " << distance[0][0];
• cout << "nDistance [0][1]" << ": " << distance[0][1];
• cout << "nDistance [0][2]" << ": " << distance[0][2];
• cout << "nDistance [0][3]" << ": " << distance[0][3];
• cout << "nDistance [1][0]" << ": " << distance[1][0];
• cout << "nDistance [1][1]" << ": " << distance[1][1];
• cout << "nDistance [1][2]" << ": " << distance[1][2];
• cout << "nDistance [1][3]" << ": " << distance[1][3];
• cout << endl; return 0;
• }
• This would produce: Members of the array
• Distance [0][0]: 44.14 Distance [0][1]: 720.52
• Distance [0][2]: 96.08 Distance [0][3]: 468.78
• Distance [1][0]: 6.28 Distance [1][1]: 68.04
• Distance [1][2]: 364.55 Distance [1][3]: 6234.12 37

38. 38
Array of Array Declarations
• An array of arrays
– An array whose elements are other arrays

39. 39
Array of Array Declarations
• Each of the rows is itself a one dimensional
array of values
scoresTable[2]
is the whole row numbered 2
scoresTable[2]
is the whole row numbered 2
scoresTable [1][3]scoresTable [1][3]

40. 40
Memory Allocation in
2-Dimensional Arrays
• Elements
stored in
rowwise order
• Also called
column major
order
location [0][4] is followed in
memory by location [1][0]
location [0][4] is followed in
memory by location [1][0]