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Programming fundamentals
week 2 : Getting Started with C++

Objective
In this chapter, you will:
• Become familiar with the basic components
and syntax of a C++ program. Explore
simple data types
• Variables declaration
• Memory used by data types
• Comments
• Escape sequence

Variables and Identifiers
• Variables have names – we call these names
identifiers.
• An identifier must begin with a letter or an
underscore _
• C++ is case sensitive upper case (capital) or
lower-case letters are considered different
characters. Average, average and AVERAGE are
three different identifiers.
• Identifiers cannot be reserved words (special
words like int, main, etc.)
• Two predefined identifiers are cout and cin

4
Variables and Identifiers
(continued)
• The following are legal identifiers in C++:
– first
– conversion
– payrate
Example of illegal identifier
Illegal identifier Description
Employee salary There can be no space between employee and salary
Hello! The exclamation mark cannot be used in an identifier
One+two The symbol + cannot be used in an idenrifie.
2nd An identifier cannot begin with a digit

5
Reserved Words (Keywords)
• Reserved words (also called keywords) are defined with
predefined meaning and syntax in the language
• Include:
• int
• float
• double
• char
• const
• void
• return

6
C++ Fundamental Data Types
• Data type: set of values together with a set of
operations
• C++ data types fall into three categories:
• Primitive data types include integer, float,
character, Boolean.
• Abstract data type include class, structure.
• Derived data types include array, function,
pointer, and reference.

7
In C++, data types are declarations for variables.
This determines the type and size of data associated
with variables. For example,
int age = 13;
Here, age is a variable of type int. meaning, the
variable can only store integers of either 2 or 4 bytes.

8
The table below shows the fundamental data types,
their meaning, and their sizes (in bytes):
Data Type Meaning Size (in bytes)
int Integer 2 or 4
float Floating-point 4
double Double floating-point 8
char Character 1
bool Boolean 1
void Empty 0

9
int Data Type
• The int keyword is used to indicate integers.
• Its size is usually 4 bytes. Meaning, it can store
values from -2147483648 to 2147483647
• Examples:
– Int salary = 85000;
• Positive integers do not need a + sign

10
• float and double are used to store floating-point
numbers (decimals and exponentials).
• The size of float is 4 bytes and the size of double
is 8 bytes. Hence, double has two times the
precision of float. To learn more, visit C++ float
and double.
• For example,
– float area = 64.74;
– double volume – 134.64534;
Floating-Point Data Types

11
char Data Type
• Keyword char is used for characters.
• Its size is 1 byte.
• Characters in C++ are enclosed inside single quotes ' '
– 'A', 'a', '0', '*', '+', '$', ‘&’
For example,
char test = ‘h’;

12
bool Data Type
• The bool data type has one of two possible values:
true or false.
• Booleans are used in conditional statements and
loops (which we will learn in later chapters).
• For example,
– bool con = false;

13
void Data Type
• The void keyword indicates an absence of data. It
means "nothing" or "no value".
• We will use void when we learn about functions
and pointers.
– Note: We cannot declare variables of the void type.

14
string Type
• Programmer-defined type supplied in Standard C++ library
• Sequence of zero or more characters
• Enclosed in double quotation marks
• Null: a string with no characters
• Each character has relative position in string
– Position of first character is 0
• Length of a string is number of characters in it
– Example: length of "William Jacob" is 13

15
Form and Style
• Consider two ways of declaring variables:
– Method 1
int feet, inch;
double x, y;
– Method 2
int a,b;double x,y;
• Both are correct; however, the second is hard to
read

Modifiers
• We can further modify some of the fundamentals data
types by using type modifiers. There are 4 type modifiers
in C++. They are:
– signed
– unsigned
– short
– long

Modified Data types List
Data Type Size (in
Bytes)
Meaning
signed int 4 Used for integers (equivalent to int0
unsigned int 4 Can only store positive integers
short 2 Used for small integers(range -32768 to 32767)
unsigned short 2 Used for small positive integers(range 0 to
65.535)
long 4 Used for large integers (equivalent to long int)
long long 8 Used for very large integers
unsigned long
long
8 Used for very large positive integers
uong double 12 Used for large floating-point numbers
signed char 1 Used for characters (range -127 to 127)

18
Use of Blanks
• In C++, you use one or more blanks to
separate numbers when data is input
• Used to separate reserved words and
identifiers from each other and from other
symbols
• Must never appear within a reserved word or
identifier

19
Constants and Variables
• Named constant: memory location whose
content can’t change during execution
• The syntax to declare a named constant is:
• In C++, const is a reserved word.
• Variable: memory location whose content
may change during execution

20
Programming Example:
Variables and Constants
• Variables
int feet; //variable to hold given feet
int inches; //variable to hold given inches
double centimeters; //variable to hold length in
//centimeters
• Named Constant
const double CENTIMETERS_PER_INCH = 2.54;
const int INCHES_PER_FOOT = 12;

21
Whitespaces
• Every C++ program contains whitespaces
– Include blanks, tabs, and newline characters
• Used to separate special symbols, reserved
words, and identifiers
• Proper utilization of whitespaces is
important
– Can be used to make the program readable

22
Declaring & Initializing
Variables
• Ways to place data into a variable:
– Use C++’s assignment statement
•feet = 35;
– Use input (read) statements
•cin >> feet;

23
Declaring & Initializing
Variables
– Use C++’s assignment statement example
int first=13, second=10;
char ch=' ';
double x=12.6;
• All variables must be initialized before they
are used
– But not necessarily during declaration

24
Input (Read) Statement
• cin is used with >> to gather input
• The stream extraction operator is >>
• For example, if miles is a double variable
cin >> miles;
– Causes computer to get a value of type
double
– Places it in the variable miles

25
Input (Read) Statement
(continued)
• Using more than one variable in cin allows
more than one value to be read at a time
• For example, if feet and inches are
variables of type int, a statement such as:
cin >> feet >> inches;
– Inputs two integers from the keyboard
– Places them in variables feet and inches
respectively

26
Output
• The syntax of cout and << is:
– Called an output statement
• The stream insertion operator is <<
• Expression evaluated and its value is
printed at the current cursor position on the
screen

27
Output (continued)
• A manipulator is used to format the output
– endl causes insertion point to move to
beginning of next line
– Example:

28
Output (continued)
• The new line character is 'n'
– May appear anywhere in the string
cout << "Hello there.";
cout << "My name is James.";
• Output:
Hello there.My name is James.
cout << "Hello there.n";
cout << "My name is James.";
• Output :
Hello there.
My name is James.

30
Comments
• Comments are for the reader, not the compiler
• Two types:
– Single line
// This is a C++ program. It prints the sentence:
// Welcome to C++ Programming.
– Multiple line
/*
You can include comments that can
occupy several lines.
*/

31
Documentation
• A well-documented program is easier to
understand and modify
• You use comments to document programs
• Comments should appear in a program to:
– Explain the purpose of the program
– Identify who wrote it
– Explain the purpose of particular statements

32
Preprocessor Directives
• C++ has a small number of operations
• Many functions and symbols needed to run a C++
program are provided as collection of libraries
• Every library has a name and is referred to by a
header file
• Preprocessor directives are commands supplied to
the preprocessor
• All preprocessor commands begin with #
• No semicolon at the end of these commands

33
Preprocessor Directives
(continued)
• Syntax to include a header file:
• For example:
#include <iostream>
The #include is a preprocessor directive used to include files
in our program. This allows us to use cout in our program
to print output on the screen and cin to take input from
user.

34
namespace and Using cin and
cout in a Program
• cin and cout are declared in the header file
iostream, but within std namespace
• To use cin and cout in a program, use the
following two statements:
#include <iostream>
using namespace std;
• using namespace std means that we can use
names for objects and variables from the standard
library.

35
Creating a C++ Program
• C++ program has two parts:
– Preprocessor directives
– The program
• Preprocessor directives and program statements
constitute C++ source code (.cpp)
• Executable code is produced and saved in a file
with the file extension .exe

36
(continued)
• A C++ program is a collection of functions, one of which
is the function main
• The first line of the function main is called the heading of
the function:
int main()
• The statements enclosed between the curly braces ({ and
}).
• A valid C++ program must have the main() function. The
curly braces indicate the start and the end of the function.
• The execution of code beings from this function.

37
Example: Body of the Function
Program:
#include <iostream>
using namespace std;
int main(){
cout<<“Hello World”;
}
Output:
Hello World

38
(continued)

39
(continued)
Sample Run:
Line 9: firstNum = 18
Line 10: Enter an integer: 15
Line 13: secondNum = 15
Line 15: The new value of firstNum = 60

40
Program Style and Form
• Every C++ program has a function main
• It must also follow the syntax rules
• Other rules serve the purpose of giving
precise meaning to the language

41
Use of Semicolons, Brackets, and
Commas
• All C++ statements end with a semicolon
– Also called a statement terminator
• { and } are not C++ statements
• Commas separate items in a list

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