Announcements Starting next week class 6-8 on Thursday Homework 1 on the web  Due January 29 – next class meeting  Homework policy No late assignments Graded out of 10 points Receive 5 points for turning it in

Lecture 2

Topics of this lecture Introduce first program  Explore inputs and outputs of a program Arithmetic using C++ Introduce the conditional statement

General Notes About C++ and This Book Book geared toward novice programmers  Stress programming clarity  C and C++ are portable languages Portability  C and C++ programs can run on many different computers Compatibility  Many features of current versions of C++ not compatible with older implementations

Introduction to C++ Programming C++ language  Facilitates structured and disciplined approach to computer program design Following several examples  Illustrate many important features of C++  Each analyzed one statement at a time Structured programming Object-oriented programming

A Simple Program: Printing a Line of Text Comments  Document programs  Improve program readability  Ignored by compiler  Single-line comment Begin with // Preprocessor directives  Processed by preprocessor before compiling  Begin with #

Basics of a Typical C++ Environment Input/output  cin Standard input stream Normally keyboard  cout Standard output stream Normally computer screen  cerr Standard error stream Display error messages

fig01_02.cpp (1 of 1) fig01_02.cpp output (1 of 1) 1 // Fig. 1.2: fig01_02.cpp 2 // A first program in C++. 3 #include 4 5 // function main begins program execution 6 int main() 7 { 8 std::cout << "Welcome to C++!\n"; 9 10 return 0; // indicate that program ended successfully } // end function main Welcome to C++! Single-line comments.Preprocessor directive to include input/output stream header file. Function main appears exactly once in every C++ program.. Function main returns an integer value. Left brace { begins function body. Corresponding right brace } ends function body. Statements end with a semicolon ;. Name cout belongs to namespace std. Stream insertion operator. Keyword return is one of several means to exit function; value 0 indicates program terminated successfully.

A Simple Program: Printing a Line of Text Standard output stream object  std::cout  “Connected” to screen  << Stream insertion operator Value to right (right operand) inserted into output stream Namespace  std:: specifies using name that belongs to “namespace” std  std:: removed through use of using statements Escape characters  \  Indicates “special” character output

A Simple Program: Printing a Line of Text Make some modifications to First Program

Another Simple Program: Adding Two Integers Variables  Location in memory where value can be stored  Common data types int - integer numbers char - characters double - floating point numbers  Declare variables with name and data type before use int integer1; int integer2; int sum;  Can declare several variables of same type in one declaration Comma-separated list int integer1, integer2, sum;

Another Simple Program: Adding Two Integers Variables  Variable names Valid identifier  Series of characters (letters, digits, underscores)  Cannot begin with digit  Case sensitive

Another Simple Program: Adding Two Integers Input stream object  >> (stream extraction operator) Used with std::cin Waits for user to input value, then press Enter (Return) key Stores value in variable to right of operator  Converts value to variable data type = (assignment operator)  Assigns value to variable  Binary operator (two operands)  Example: sum = variable1 + variable2;

1 // Fig. 1.6: fig01_06.cpp 2 // Addition program. 3 #include 4 // function main begins program execution 5 int main() { 6 int integer1; // first number to be input by user 7 int integer2; // second number to be input by user 8 int sum; // variable in which sum will be stored 9 10 std::cout << "Enter first integer\n"; // prompt 11 std::cin >> integer1; // read an integer std::cout << "Enter second integer\n"; // prompt 14 std::cin >> integer2; // read an integer sum = integer1 + integer2; // assign result to sum 17 std::cout << "Sum is " << sum << std::endl; // print sum return 0; // indicate that program ended successfully 20 } // end function main Declare integer variables.Use stream extraction operator with standard input stream to obtain user input. Stream manipulator std::endl outputs a newline, then “flushes output buffer.” Concatenating, chaining or cascading stream insertion operations. Calculations can be performed in output statements: alternative for lines 18 and 20: std::cout << "Sum is " << integer1 + integer2 << std::endl; fig01_06.cpp (1 of 1)

Microsoft Visual C++ numeric data types Type NameBytesOther NamesRange of Values int*signed, signed intSystem dependent unsigned int*unsignedSystem dependent __int81char, signed char–128 to 127 __int162short, short int, signed short int –32,768 to 32,767 __int324signed, signed int–2,147,483,648 to 2,147,483,647 __int648none–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 char1signed char–128 to 127 unsigned char1none0 to 255

Type Name BytesOther NamesRange of Values short2short int, signed short int –32,768 to 32,767 unsigned short2unsigned short int0 to 65,535 long4long int, signed long int–2,147,483,648 to 2,147,483,647 unsigned long4unsigned long int0 to 4,294,967,295 enum*noneSame as int float4none3.4E +/- 38 (7 digits) double8none1.7E +/- 308 (15 digits) long double10none1.2E +/ (19 digits) Microsoft Visual C++ numeric data types

Memory Concepts Variable names  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 nondestructive

Memory Concepts std::cin >> integer1;  Assume user entered 45 std::cin >> integer2;  Assume user entered 72 sum = integer1 + integer2; integer1 45 integer1 45 integer2 72 integer1 45 integer2 72 sum 117

Effect of Several Assignments What are the values of a and b after all statements are executed? int a = 1; int b; b = a; a = 2; a = 2, b = 1

Arithmetic Arithmetic calculations  * Multiplication  / Division Integer division truncates remainder  7 / 5 evaluates to 1  % Modulus operator returns remainder  7 % 5 evaluates to 2

Arithmetic Rules of operator precedence  Operators in parentheses evaluated first Nested/embedded parentheses  Operators in innermost pair first  Multiplication, division, modulus applied next Operators applied from left to right  Addition, subtraction applied last Operators applied from left to right X = / 2 * (3 * ( 4 – 3) + 5) % 2 + 3

Decision Making: Equality and Relational Operators if structure  Make decision based on truth or falsity of condition If condition met, body executed Else, body not executed Equality and relational operators  Lower precedence than arithmetic operators  Equality operators Same level of precedence  Relational operators Same level of precedence  Associate left to right

Decision Making: Equality and Relational Operators Notice: “==“ (not “=“)

Decision Making: Equality and Relational Operators using statements  Eliminate the need to use the std:: prefix  Allow us to write cout instead of std::cout  To use the following functions without the std:: prefix, write the following at the top of the program using std::cout; using std::cin; using std::endl; Look at example program

Thinking About Objects: Introduction to Object Technology and the Unified Modeling Language Object orientation  Natural way to think about the world and to write computer programs  Attributes - properties of objects Size, shape, color, weight, etc.  Behaviors - actions A ball rolls, bounces, inflates and deflates Objects can perform actions as well  Inheritance New classes of objects absorb characteristics from existing classes  Information hiding Objects usually do not know how other objects are implemented

Thinking About Objects: Introduction to Object Technology and the Unified Modeling Language Abstraction - view the big picture  See a photograph rather than a group of colored dots  Think in terms of houses, not bricks Class - unit of programming  Classes serve as a “Blueprint" of objects Objects are created from a class  Classes contain functions Used to implement behaviors  Classes contain data Used to implement attributes  Classes are reusable

Thinking About Objects: Introduction to Object Technology and the Unified Modeling Language Unified Modeling Language (UML)  Used to model object-oriented systems and aid with their design  Complex, feature-rich graphical language