1 Topic 2 Beginning With C Outline 2

1 Topic 2– Beginning With C++ Outline 2. 1 What is C++ 2. 2 Applications of C++ 2. 3 A Simple C++ Program 2. 4 More C++ Statements 2. 5 Compiling & Linking

2 2. 1 What is C++ • History of C++ – Extension of C – Early 1980 s: Bjarne Stroustrup (Bell Laboratories) – Provides capabilities for object-oriented programming • Objects: reusable software components – Model items in real world • Object-oriented programs – Easy to understand, correct and modify – Hybrid language • C-like style • Object-oriented style • Both

3 2. 2 Applications of C++ • Versatile Language – Suitable for developing editors, Compilers, databases, Communication Systems – Can create hierarchy-related objects – Can Map real world problems – Easy to maintain and expand – General Purpose language

2. 3 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 # 4

1 2 3 // Fig. 1. 2: fig 01_02. cpp // A first program in C++. Function main #include <iostream> 4 5 6 7 8 // function main int main() { std: : cout << "Welcome to C++!n"; 9 10 11 12 5 Single-line comments. returns an directive to integer value. Left brace { begins Preprocessor function include input/output Statements stream begins execution Function main appears body. program end with a header file <iostream>. exactly once in every C++ semicolon ; . program. . return 0; // } // end function Welcome to C++! Corresponding right brace } indicate thatbody. program ended successfully ends function Stream insertion Name cout belongs to operator. main namespace std. Keyword return is one of several means to exit function; value 0 indicates program terminated successfully.

2. 3 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 6

7 2. 4 More C++ Statements

1 2 3 // Fig. 1. 4: fig 01_04. cpp // Printing a line with multiple statements. #include <iostream> 4 5 6 7 8 9 // function main begins program execution int main() { std: : cout << "Welcome "; std: : cout << "to C++!n"; 10 11 12 13 return 0; Multiple stream insertion statements produce one line of output. // indicate that program ended successfully } // end function main Welcome to C++! 8

1 2 3 // Fig. 1. 5: fig 01_05. cpp // Printing multiple lines with a single statement #include <iostream> 4 5 6 7 8 // function main begins program execution Using newline characters print on multiple lines. int main() { std: : cout << "Welcomentonn. C++!n"; 9 10 11 12 return 0; // indicate that program ended successfully } // end function main Welcome to C++! 9 to

10 2. 4 More C++ Statements • 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 integer 1; integer 2; int sum; – Can declare several variables of same type in one declaration • Comma-separated list integer 1, integer 2, sum;

11 2. 4 More C++ Statements • Variables – Variable names • Valid identifier – Series of characters (letters, digits, underscores) – Cannot begin with digit – Case sensitive

12 2. 4 More C++ Statements • 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 = variable 1 + variable 2;

13 1 2 3 // Fig. 1. 6: fig 01_06. cpp // Addition program. #include <iostream> 4 5 6 7 8 9 10 // function main begins program execution int main() Declare integer variables. { integer 1; // first number to be input by user integer 2; // second number to be input by user Usewhich stream extraction int sum; // variable in sum will be operator stored with standard input stream to obtain user input. integern"; // prompt 11 12 13 std: : cout << "Enter first std: : cin >> integer 1; 14 15 16 std: : cout << "Enter second integern" ; // prompt std: : cin >> integer 2; // read an integer Calculations can be performed in output 17 18 sum = integer 1 + integer 2; 19 20 std: : cout << "Sum is " << sum << std: : endl; // print 21 22 return 0; 23 24 // read an integer lines 18 and 20: // assign result to sum statements: alternative for Stream manipulator std: : endl outputs a newline, then “flushes output integer 1 + integer 2 << std: : endl; sum buffer. ” // indicate that program ended successfully } // end function main Concatenating, chaining or cascading stream insertion operations.

Enter first integer 45 Enter second integer 72 Sum is 117 14

15 2. 4 More C++ Statements • Arithmetic calculations – * • Multiplication – / • Division • Integer division truncates remainder – 7 / 5 evaluates to 1 – % • Modulus operator returns remainder – 7 % 5 evaluates to 2

16 2. 4 More C++ Statements • 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

17 2. 4 More C++ Statements • if structure – Make decision based on truth or falsity of condition • If condition met, body executed • Else, body not executed • Equality and relational operators – Equality operators • Same level of precedence – Relational operators • Same level of precedence – Associate left to right

18 2. 4 More C++ Statements

19 2. 4 More C++ Statements • using statements – Eliminate use of std: : prefix – Write cout instead of std: : cout

20 1 2 3 4 // Fig. 1. 14: fig 01_14. cpp // Using if statements, relational // operators, and equality operators. #include <iostream> 5 6 7 8 using std: : cout; using std: : cin; using std: : endl; 9 10 11 12 13 14 variables. // function main begins program. Declare execution int main() { Can write cin int num 1; // first number to becout read and from user without std: : prefix. int num 2; // second number to be read from user // program uses cout // program uses cin // program uses endl using statements eliminate need for std: : prefix. 15 16 17 18 cout << "Enter two integers, and I will tell youn" if structure compares values << "the relationships they satisfy: " ; of num 1 and num 2 to test for If condition is true cin >> num 1 >> num 2; // read two integers 19 20 21 if ( num 1 == num 2 ) cout << num 1 << " is 22 23 24 if ( num 1 != num 2 ) cout << num 1 << " is not equal to " << num 2 << endl; 25 (i. e. , values equality. are equal), execute this if structure compares values statement. of num 1 andnum 2 test for If condition is true (i. e. , values equal to " << << to endl; are not equal), execute this inequality. statement.

26 27 if ( num 1 < num 2 ) cout << num 1 << " is less than " << num 2 << endl; 28 29 30 if ( num 1 > num 2 ) cout << num 1 << " is greater than " << num 2 << endl; 31 32 33 34 if ( num 1 <= num 2 ) cout << num 1 << " is less than or equal to " << num 2 << endl; 35 36 37 38 if ( num 1 >= num 2 ) cout << num 1 << " is greater than or equal to " << num 2 << endl; 39 40 return 0; 41 42 // indicate that program ended successfully } // end function main Enter two integers, and I will tell you the relationships they satisfy: 22 12 22 is not equal to 12 22 is greater than or equal to 12 21 Statements may be split over several lines.

Enter two integers, and I will tell you the relationships they satisfy: 7 7 7 is equal to 7 7 is less than or equal to 7 7 is greater than or equal to 7 22

23 2. 5 Compiling & Linking Phases of C++ Programs: 1. Edit 2. Preprocess 3. Compile Editor Preprocessor Compiler Linker 4. Link Loader 5. Load Disk 6. Execute Disk Program is created in the editor and stored on disk. Disk Preprocessor program processes the code. Disk Compiler creates object code and stores it on disk. Disk Primary Memory Linker links the object code with the libraries, creates a. out and stores it on disk Loader puts program in memory. . . . Primary Memory CPU . . . CPU takes each instruction and executes it, possibly storing new data values as the program executes.

24 2. 5 Compiling & Linking • • Unix AT & T C++ Turbo C++ & Borland C++ Visual C++ Eclipse