Lecture # 1 introduction revision - 1

CS-200
Object Oriented Programming
4(3+1)
MuhammadUsman
MS(Computer Science) – Artificial Intelligence

Course Objectives
 Understand object-oriented programming features in C++
 Apply these features to program design and implementation
 Understand object-oriented concepts and how they are
supported by C++
 Gain some practical experience of C++
 Understand implementation issues related to object-oriented
techniques
 Build good quality software using object-oriented techniques
 Understand the role of patterns in object-orienteddesign.

Textbook and Tools
Textbook
 Object-OrientedProgramming in C++
4th Ed., Robert Lafore; SAMS Publishing
 C++ How to Programming
9th Editionby Deitel & Deitel
Programming Tools
 Dev C++
 Microsoft Visual Studio

Mid-Term
Examination
30% 30 Marks
Assignments &
Quizzes
20%
20 Marks
4 Quizzes (10 Marks)
(2 Quiz before Mid & 2 Quiz After Mid)
4 Assignments (10 Marks)
(2 Assignments before Mid & 2 Assignments After Mid)
Final Examination 50% (25 % of Mid-Term Must Include) 50 Marks
Class Evaluation and Contact
 Contact
 Class Representative(s)
 mhmdusmaan@gmail.com / muhammad.usman@abasynisb.edu.pk

Introduction to C++
C++ Origins
Low-level languages
Machine, assembly
High-level languages
 C, C++, ADA, COBOL, FORTRAN
Object-Oriented-Programming in C++
C++ Terminology
Programs and functions
Basic Input/Output (I/O) with cin and cout

Display 1.1
A Sample C++ Program (1 of 2)

Display 1.1
A Sample C++ Program (2 of 2)

Constants
Naming your constants
Literal constants are "OK", but provide
little meaning
e.g., seeing 24 in a pgm, tells nothing about
what it represents
Use named constants instead
Meaningful name to represent data
const int NUMBER_OF_STUDENTS = 24;
Called a "declared constant" or "named constant"
Now use it’s name wherever needed in program
Added benefit: changes to value result in one fix

Arithmetic Operators:
Display 1.4 Named Constant (1 of 2)
 Standard Arithmetic Operators
 Precedence rules – standard rules

Arithmetic Operators:
Display 1.4 Named Constant (2 of 2)

C++ Variables
C++ Identifiers
Keywords/reserved words vs. Identifiers
Case-sensitivity and validity of identifiers
Meaningful names!
Variables
A memory location to store data for a program
Must declare all data before use in program

Data Types:
Display 1.2 Simple Types (1 of 2)

Data Types:
Display 1.2 Simple Types (2 of 2)

Assigning Data
Initializing data in declaration statement
Results "undefined" if you don’t!
int myValue = 0;
Assigning data during execution
Lvalues (left-side) & Rvalues (right-side)
Lvalues must be variables
Rvalues can be any expression
Example:
distance = rate * time;
Lvalue: "distance"
Rvalue: "rate * time"

Assigning Data: Shorthand Notations

Data Assignment Rules
Compatibility of Data Assignments
Type mismatches
General Rule: Cannot place value of one type into variable of
another type
intVar = 2.99; // 2 is assigned to intVar!
Only integer part "fits", so that’s all that goes
Called "implicit" or "automatic type conversion"
Literals
2, 5.75, "Z", "Hello World"
Considered "constants": can’t change in program

Literal Data
Literals
Examples:
2 // Literal constant int
5.75 // Literal constant double
"Z" // Literal constant char
"Hello World" // Literal constant string
Cannot change values during execution
Called "literals" because you "literally typed"
them in your program!

Escape Sequences
 "Extend" character set
 Backslash, preceding a character
 Instructs compiler: a special "escape
character" is coming
 Following character treated as
"escape sequence char"
 Display 1.3 next slide

Display 1.3
Some Escape Sequences (1 of 2)

Display 1.3
Some Escape Sequences (2 of 2)

Arithmetic Precision
 Precision of Calculations
 VERY important consideration!
Expressions in C++ might not evaluate as you’d "expect"!
 "Highest-orderoperand" determines type of arithmetic"precision"
performed
 Commonpitfall!

Arithmetic Precision Examples
Examples:
17 / 5 evaluates to 3 in C++!
Both operands are integers
Integer division is performed!
17.0 / 5 equals 3.4 in C++!
Highest-order operand is "double type"
Double "precision" division is performed!
int intVar1 =1, intVar2=2;
intVar1 / intVar2;
Performs integer division!
Result: 0!

Individual Arithmetic Precision
Calculations done "one-by-one"
1 / 2 / 3.0 / 4 performs 3 separate divisions.
First→ 1 / 2 equals 0
Then→ 0 / 3.0 equals 0.0
Then→ 0.0 / 4 equals 0.0!
So not necessarily sufficient to change
just "one operand" in a large expression
Must keep in mind all individual calculations
that will be performed during evaluation!

Type Casting
Casting for Variables
Can add ".0" to literals to force precision
arithmetic, but what about variables?
We can’t use "myInt.0"!
static_cast<double>intVar
Explicitly "casts" or "converts" intVar to
double type
Result of conversion is then used
Example expression:
doubleVar = static_cast<double>intVar1 / intVar2;
 Casting forces double-precision division to take place
among two integer variables!

Type Casting
Two types
Implicit—also called "Automatic"
Done FOR you, automatically
17 / 5.5
This expression causes an "implicit type cast" to
take place, casting the 17 → 17.0
Explicit type conversion
Programmer specifies conversion with cast operator
(double)17 / 5.5
Same expression as above, using explicit cast
(double)myInt / myDouble
More typical use; cast operator on variable

Shorthand Operators
 Increment & Decrement Operators
 Just short-hand notation
 Increment operator, ++
intVar++; is equivalent to
intVar = intVar + 1;
 Decrement operator, --
intVar--; is equivalent to
intVar = intVar – 1;

Shorthand Operators: Two Options
Post-Increment
intVar++
Uses current value of variable, THEN increments it
Pre-Increment
++intVar
Increments variable first, THEN uses new value
"Use" is defined as whatever "context"
variable is currently in
No difference if "alone" in statement:
intVar++; and ++intVar; → identical result

Post-Increment in Action
Post-Increment in Expressions:
int n = 2,
valueProduced;
valueProduced = 2 * (n++);
cout << valueProduced << endl;
cout << n << endl;
This code segment produces the output:
4
3
Since post-increment was used

Pre-Increment in Action
Now using Pre-increment:
int n = 2,
valueProduced;
valueProduced = 2 * (++n);
cout << valueProduced << endl;
cout << n << endl;
This code segment produces the output:
6
3
Because pre-increment was used

Console Input/Output
I/O objects cin, cout, cerr
Defined in the C++ library called
<iostream>
Must have these lines (called pre-
processor directives) near start of file:
#include <iostream>
using namespace std;
Tells C++ to use appropriate library so we can
use the I/O objects cin, cout, cerr

Console Output
What can be outputted?
Any data can be outputted to display screen
Variables
Constants
Literals
Expressions (which can include all of above)
cout << numberOfGames << " games played.";
2 values are outputted:
"value" of variable numberOfGames,
literal string " games played."
Cascading: multiple values in one cout

Separating Lines of Output
New lines in output
Recall: "n" is escape sequence for the
char "newline"
A second method: object endl
Examples:
cout << "Hello Worldn";
Sends string "Hello World" to display, & escape
sequence "n", skipping to next line
cout << "Hello World" << endl;
Same result as above

Formatting Output
 Formatting numeric values for output
 Values may not display as you’d expect!
cout << "The price is $" << price << endl;
If price (declared double) has value78.5, you
might get:
 The price is $78.500000 or:
 The price is $78.5
 We must explicitly tell C++ how to output numbers in our
programs!

Input Using cin
cin for input, cout for output
Differences:
">>" (extraction operator) points opposite
Think of it as "pointing toward where the data goes"
Object name "cin" used instead of "cout"
No literals allowed for cin
Must input "to a variable"
cin >> num;
Waits on-screen for keyboard entry
Value entered at keyboard is "assigned" to num

Prompting for Input: cin and cout
Always "prompt" user for input
cout << "Enter number of dragons: ";
cin >> numOfDragons;
Note no "n" in cout. Prompt "waits" on same
line for keyboard input as follows:
Enter number of dragons: ____
Underscore above denotes where keyboard entry
is made
Every cin should have cout prompt
Maximizes user-friendly input/output

Program Style
 Bottom-line: Make programs easy to read and modify
 Comments, two methods:
 // Two slashes indicate entire line is to be ignored
 /*Delimiters indicates everything between is ignored*/
 Both methods commonly used
 Identifier naming
 ALL_CAPS for constants
 lowerToUpper for variables
 Most important: MEANINGFUL NAMES!

Libraries
 C++ Standard Libraries
 #include <Library_Name>
 Directive to"add" contents of library file to
your program
 Called "preprocessor directive"
Executes before compiler, and simply "copies"
library file into your program file
 C++ has many libraries
 Input/output, math, strings, etc.

Namespaces
 Namespaces defined:
 Collection of name definitions
 For now: interested in namespace "std"
 Has all standard library definitions we need
 Examples:
#include <iostream>
using namespace std;
 Includes entire standard library of name definitions
 #include <iostream>
using std::cin;
using std::cout;
 Can specify just the objects we want

Summary 1
 C++ is case-sensitive
 Use meaningful names
 For variables and constants
 Variables must be declared before use
 Should also be initialized
 Use care in numeric manipulation
 Precision, parentheses, order of operations
 #include C++ libraries as needed

Summary 2
Object cout
Used for console output
Object cin
Used for console input
Use comments to aid understanding of
your program
Do not overcomment

Lecture # 1 introduction revision - 1

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