Transcript Data Structures

CPS120: Introduction to
Computer Science
Lecture 15A
Structures
Pointer Use in C++.
A pointer is a variable or constant
that holds a memory address
a) Hexadecimal numbers are used for
representing memory locations
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i
iptr
Using Pointers
Pointers must be initialized
e.g. iptr =&I;
This reads iptr is assigned the address of i
Intializing Pointers
Declare pointers before use, as with
other variables.
Each variable being declared as a
pointer must be preceded by an
asterisk (*).
Initialize pointers before use to a 0,
NULL or an address to prevent
unexpected results
Pointer Operators
& is the address operator which
returns the address of its operand
* is the indirection operator or
dereferencing operator and returns
the value to which the operand
(pointer) points.
sizeof - used to determine the size of
an array during program compiliation
Relationship between Pointers
and Arrays
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I
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state_code
C++ and Strings
C++ numbers the individual characters in a
string beginning with index position 0. So
after the declaration statement,
string stateName = "Michigan";
is made, the 'M' is considered to be in the
index position 0, the first 'i' in the index
position 1, the 'c' in the index position 2, and so
on. Note that index positions may contain a
blank space, which is, of course, a valid
character. A blank space has an ASCII value of
32.
Changing Values in an Array
You may use subscript notation to change
the value of one specific character within a
string. The assignment statement,
stateName[1] = 'I';
would change the lowercase e originally
found in index position 1 of the example
above to an uppercase I. So the string is
now "MIchigan".
Using enum
enum allows you to create your own simple
data types for special purposes
Create a type
Give it a name
Specify values that are acceptable
enum sizes {small, medium, large, jumbo};
The compiler assigns an integer to each enum
item
typedef
typedef gives a new name to an
existing data type
typedef float real;
Confusing to the reader, should be
used sparingly
Structures
Structures group variables together in
order to make one's programming task
more efficient.
Any combination of variables can be combined
into one structure.
This is a useful and efficient way to store data.
struct Student
{
string socSecNum;
string lastName;
string firstName;
int pointsEarned;
double gpa;
};
Using Structures
Each of the different variables are called
members of the structure
Structures allow us to keep related data
referring to individual members together
Strings, integer, and floating-point
variables may be grouped together into one
structure.
In effect, we have created our own customized
data type.
The semicolon after the closing curly brace
is required
Using the new data structure
The structure definition should be placed
above the main function of a program but
below the compiler directives
Declare an actual variable of this
programmer-created data type within a
function (such as main) in order to make
use of this structureDone with a
declaration statement like
Student freshmen;
This reates a variable called freshmen of
the data type Student
Assigning values to the structure
To assign a grade point average (GPA) of
3.4 to the gpa member of the variable
freshmen, use the statement:
freshmen.gpa = 3.4;
The period (.) that is used between the
variable name freshmen and the member
gpa is called the dot operator.
The dot operator simply us to reference
individual members of a structure
Nested Structures
You can use a previously defined structure as a member of another
structure
Address is nested inside of the Customer structure.
Since Address is used within Customer, the structure definition for
Address must be placed above Customer in order to avoid compile
errors
struct Address
{
string street;
string city;
string state;
int zip;
};
struct Customer
{
string name;
string phone;
Address homeAddress;
Address businessAddress; };