2. 2
C++ has a large number of fundamental or built-in object types
The fundamental object types fall into one of three categories
Integer objects
Floating-point objects
Character objects
Integer object type
The basic integer object type is int
The size of an int depends on the machine and the compiler
On PCs it is normally 16 or 32 bits
Other integers object types
short: typically uses less bits (often 2 bytes)
long: typically uses more bits (often 4 bytes)
Different types allow programmers to use resources more efficiently
Standard arithmetic and relational operations are available for these
types
Fundamental C++ Objects
3. 3
Integer constants
Integer constants are positive or negative whole numbers
Integer constant forms
Decimal
Digits 0, 1, 2, 3, 4, 5, 6, 7
Octal (base 8)
Digits 0, 1, 2, 3, 4, 5, 6, 7
Hexadecimal (base 16)
Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a , b, c, d, e, f, A, B, C, D, E, F
Consider
31 oct and 25 dec
Decimal Constants
Examples
97
40000
50000
23a (illegal)
The type of the constant depends on its size, unless the type is
specified
4. 4
Character object type
Char is for specifying character data
char variable may hold only a single lowercase letter, a single
upper case letter, a single digit, or a single special character
like a $, 7, *, etc.
case sensitive, i.e. a and A are not same.
ASCII is the dominant encoding scheme
Examples
' ' encoded as 32 '+' encoded as 43
'A' encoded as 65 'Z' encoded as 90
'a' encoded as 97 'z' encoded as 122
5. 5
Character object type
Explicit (literal) characters within single quotes
'a','D','*‘
Special characters - delineated by a backslash
Two character sequences (escape codes)
Some important special escape codes
t denotes a tab n denotes a new line
denotes a backslash ' denotes a single quote
" denotes a double quote
't' is the explicit tab character, 'n' is the explicit
new line character, and so on
6. 6
Floating-point object
Floating-point object types represent real numbers
Integer part
Fractional part
The number 108.1517 breaks down into the following parts
108 - integer part
1517 - fractional part
C++ provides three floating-point object types
Float
(often 4 bytes) Declares floating point numbers with up to 7 significant digits
Double
long double
(often 10 bytes) Declares floating point numbers with up to 19 significant digits.
7. 7
Memory Concepts
Variable
Variables are names of memory locations
Correspond to actual locations in computer's memory
Every variable has name, type, size and value
When new value placed into variable, overwrites previous value
Reading variables from memory is nondestructive
cin >> integer1;
Assume user entered 45
cin >> integer2;
Assume user entered 72
sum = integer1 + integer2;
integer1 45
integer2 72
integer1 45
sum 117
integer2 72
integer1 45
8. 8
Names (naming entities)
Used to denote program values or components
A valid name is a sequence of
Letters (upper and lowercase)
A name cannot start with a digit
Names are case sensitive
MyObject is a different name than MYOBJECT
There are two kinds of names
Keywords
Identifiers
9. 9
Keywords
Keywords are words reserved as part of the language
int, return, float, double
They cannot be used by the programmer to name things
They consist of lowercase letters only
They have special meaning to the compiler
10. 10
C++ key words
C++ Keywords
Keywords common to the
C and C++ programming
languages
auto break case char const
continue default do double else
enum extern float for goto
if int long register return
short signed sizeof static struct
switch typedef union unsigned void
volatile while
C++ only keywords
asm bool catch class const_cast
delete dynamic_cast explicit false friend
inline mutable namespace new operator
private protected public reinterpret_cast
static_cast template this throw true
try typeid typename using virtual
wchar_t
11. 11
Identifiers
Identifiers are used to name entities in c++
It consists of letters, digits or underscore
Starts with a letter or underscore
Can not start with a digit
Identifiers should be
Short enough to be reasonable to type
Standard abbreviations are fine (but only standard abbreviations)
Long enough to be understandable
When using multiple word identifiers capitalize the first letter of each
word
Examples
Grade
Temperature
CameraAngle
IntegerValue
12. 12
Definitions/declaration
All objects (or variable)
that are used in a program
must be defined (declared)
An object definition specifies
Type
Identifier
General definition form
Type Id, Id, ..., Id;
Known
type
List of one or
more identifiers
(Value of an object is whatever is in
its assigned memory location)
Examples
Char Response;
int MinElement;
float Score;
float Temperature;
int i;
int n;
char c;
float x;
Location in memory
where a value can
be stored for
program use
13. 13
Type compatibilities
Rule is to store the values in variables of the same type
This is a type mismatch:
int int_variable;
int_variable = 2.99;
If your compiler allows this, int variable will
most likely contain the value 2, not 2.99
14. 14
Stream extraction and assignment operator
>> (stream extraction operator)
When used with cin, waits for the user to input a value and
stores the value in the variable to the right of the operator
The user types a value, then presses the Enter (Return) key to
send the data to the computer
Example:
int myVariable;
cin >> myVariable;
Waits for user input, then stores input in myVariable
= (assignment operator)
Assigns value to a variable
Binary operator (has two operands)
Example:
sum = variable1 + variable2;
15. 15
A simple program to add two numbers
1//example
2// program to add two numbers
3#include <iostream.h>
4
5int main()
6{
7 int integer1, integer2, sum; // declaration
8
9 cout << "Enter first integern"; // prompt
10 cin >> integer1; // read an integer
11 cout << "Enter second integern"; // prompt
12 cin >> integer2; // read an integer
13 sum = integer1 + integer2; // assignment of sum
14 cout << "Sum is " << sum << endl; // print sum
15
16 return 0; // indicate that program ended successfully
17 }
•Notice how cin is used to get user input.
General form is cin>>identifier;
•Cin is an I stream object
•streams input from standard input
•uses the >> (input operator)
•Note that data entered from the keyboard
must be compatible with the data type of the
variable
endl flushes the buffer and prints a
newline.
•Variables can be output using cout << variableName.
•Generl form is cout<<expression;
•An expression is any c++ expression(string constant,
identifier, formula or function call)
•Cout is an o stream object
•streams output to standard output
•uses the << (output) operator
Calculations can be performed in output statements: alternative for
lines 13 and 14:
cout << "Sum is " << integer1 + integer2 << std::endl;
Use stream extraction
operator with standard input
stream to obtain user input.
Concatenating, chaining or
cascading stream insertion
operations.
19. 19
Program to find total number of students in all sections
1. //example
2. //to find the total number of students in all sections.
3. # include <iostream> //preprocessor directive
4. int main()
5. {
6. int number_of_sections, students_per_section; //declaration
7. int total_students;
8. cout<<"enter the number of sectionsn"; //prompt to enter total number of
sections
9. cin>>number_of_sections; //reading number of sections
10. cout<<"enter the number of students per sectionn"; //prompt to enter number
11. // of students per section
12. cin>>students_per_section; //reading students per section
13.
14. total_students = number_of_sections * students_per_section; //assignment to total
students
15. cout<<"total number of students in all the sections isn"; //prompt
16. cout<<total_students; // show the number of
total students
17. return 0;
18. }
