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 preprocessor 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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