Download C++

Introducing C++ Elements
Outline
algorithms’ constructs
 General form of a C++ program {section
2.5}
 C++ language elements {section 2.1}
 Executable statements {section 2.4}
 Reserved words and symbols {section
2.2}
 Data types {section 2.3}
 Main
CSCE 106
2
Main Algorithms’ Constucts


An algorithm is written as a step-by-step
procedure (sequence) in which choices can be
made where necessary (selection), and all or
part of the algorithm can be repeated
(repetition).
Thus, the basic control structures of algorithms
are:
1- Sequence
2- Selection
3- Repetition
CSCE 106
3
Sequence
 An
algorithm is based on the
notion of sequence, which is the
ordering of steps/statements.
 Step
n cannot be started until
step n-1 is complete.
CSCE 106
4
General Form of a C++ Program
// File: filename
// Program description: ….
#include directives
using namespace std;
void main()
{
Variables declaration section
Executable statements section
}
CSCE 106
5
General Form of a C++ Program
(cont’d)
Function (a collection of related statements) is
the basic unit in C++
 A C++ program must contain a main function
void main ()
 void - function returns no value
 main - lower case followed by ()
 { } - braces define the function body

CSCE 106
6
General Form of a C++ Program
(cont’d)

General form of function body parts
 Declaration statements
 Variables and constants
 Executable statements
 C++ statements
CSCE 106
7
Comments
Comments make a program easier to
understand
 They are ignored (i.e. not translated) by the
compiler
 // used to signify a comment on a single line
 /* Text text */ used for comments on
multiple lines

CSCE 106
8
Compiler Directives
#include
 Compiler directive
 Processed during compilation process
 Instructs on what you want in the program
 #include <iostream>
 Adds library class/file called iostream to
program
 Used with < >
 Also “ “ user defined

CSCE 106
9
Program Processing Diagram
CSCE 106
10
Program Processing Diagram (2)
CSCE 106
11
<iostream>
Included in iostream


cout refers to the standard
output device; i.e. the screen
cout << "Hello!";
 << output operator
(insertion operator)
cin refers to the standard input
device; i.e. the keyboard
cin >> N1 >> N2;
 >> input operator
(extraction operator)
directs input to variable
CSCE 106
12
Executable Statements
 cout
displays output on the screen
cout << “Enter the distance in miles: ”;
 cin
gets input from the keyboard
cin >> miles;
 Assignment
kms = KM_PER_MILES * miles;
CSCE 106
13
Reserved Words and Symbols

Reserved words have special meanings
 Can NOT be used for other purposes (const,
float and void are some examples)

Special symbols / delimiters
 C++ has rules for special symbols
= * ; { } ( ) // << >> [ ] , + -
CSCE 106
14
Data Types

Predefined data types
 int
(integer)
 Positive or negative whole number
 1000
12
199 100000
 The size of an int depends on the machine and the
compiler. On a PC it is usually a word (16 bits).
 Other integers types are:
• short: uses less bits (usually a byte)
• long: typically uses more bits (usually 2 words)
CSCE 106
15
Data Types (cont’d)


float
(floating point / real number)
 Positive or negative decimal number
 10.5
1.2
100.02
99.88
 Integer part and fraction part
 The number 108.1517 breaks down into the following
parts
• 108 - integer part
• 1517 - fractional part
 Other floating-point data types are:
• double
• long double
bool
(boolean)
 true
 false
CSCE 106
16
Data Types (cont’d)

char (character)
 Represents a character
Individual character value (letter or
number)
 Character literal enclosed in single quotes
‘A’
 Characters are encoded using a scheme
where an integer represents a particular
character

CSCE 106
17
Exercise


Problem
Analyse, design (using a flow chart), and implement
(using C++) an algorithm that calculates, and outputs
the sum (sum) of three numbers (n1, n2 & n3) input
by the user.
Analysis
Input
float n1: first variable
float n2: second variable
float n3: third variable
 Output
float sum: sum of n1, n2, & n3

CSCE 106
18
Exercise (cont’d)

Design
START

#include <iostream>
using namespace std;
void main ()
{
float n1, n2, n3, sum;
cout << “Please input three numbers”;
cin >> n1 >> n2 >> n3;
INPUT
n1, n2, n3
sum = n1 + n2 +n3;
sum = n1 + n2 + n3
cout << “The sum is” << sum;
OUTPUT
sum
CSCE 106
STOP
Implementation (C++)
}
19
Addition.cpp
/* FILE: Addition.cpp
PROGRAM: Adds three numbers input by the user */
#include <iostream>
using namespace std;
void main ()
{
float n1, n2, n3, sum;
// declaring variables
cout << “Please input three numbers”;
cin >> n1 >> n2 >> n3; // inputting 3 variables
sum = n1 + n2 + n3;
// adding the 3 variables
cout << “The sum is:” << sum; // outputting sum
}
CSCE 106
20
Next lecture will be about
Arithmetic Expressions
CSCE 106
21