Introduction to C Introduced by Bjarne Stroustrup of

Introduction to C++ • Introduced by Bjarne Stroustrup of AT&T’s Bell Laboratories in mid-1980’s • Based on C • C++ extended C to support object-oriented programming Professor John Carelli Kutztown University Source: Pearson Education, Inc.

Procedural Programming • Earlier programming approach • intuitive • task based • Problem was broken into manageable sub-tasks • Code was written to accomplish each sub-task • Resulting “functions” assembled to solve overall problem • Like a recipe Professor John Carelli Kutztown University Computer Science Department

Object Oriented Programming • Newer programming approach • Data based rather than task based • Abstract objects are created • representing the data elements to be worked with • Each object is self-contained • Storing both data and procedures for manipulating the data • Details hidden from the user – i. e. a “black-box” • Objects are manipulated to solve a given problem • Advantage: “black-box” localizes software changes • Large software projects are more manageable and supportable Professor John Carelli Kutztown University Computer Science Department

C++ Language Elements • Compiler directives • Function main • Declaration statements • Executable statements /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; // Convert the distance to kilometers. kms = km_per_mile * miles; • Example: miles. cpp // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } Professor John Carelli return 0; Kutztown University Source: Pearson Education, Inc.

Comments • // symbols indicate a line comment apply to just the rest of the line • Block comments start with /* and end with */ - apply to as many lines as you like • Used to describe the code in English or provide non-code information • E. g. to include the name of the program or the author’s name /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; // Convert the distance to kilometers. kms = km_per_mile * miles; // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } Professor John Carelli return 0; Kutztown University Source: Pearson Education, Inc.

#include • Compiler directive • Includes previously written code from a library into your program • Libraries allow for code reuse /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; • E. g. • #include <iostream> • has operators for performing input and output within the program • The compiler knows where to locate libraries enclosed in <> • iostream will be needed in our programs in order to use cin and cout, as shown … Professor John Carelli // Convert the distance to kilometers. kms = km_per_mile * miles; // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } return 0; Kutztown University Source: Pearson Education, Inc.

using namespace std; • Indicates to compiler that this program uses objects defined by a standard namespace called std. • i. e. a portion of the iostream library /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; • Ends with a semicolon • Follows #include directives in the code // Convert the distance to kilometers. kms = km_per_mile * miles; // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } Professor John Carelli return 0; Kutztown University Source: Pearson Education, Inc.

Function main() /* miles. cpp - convert distance in miles to kilometers. */ • Exactly one main function per program #include <iostream> // class for stream input/output using namespace std; // use the standard namespace • A function is a collection of related statements that perform a specific set of tasks • int indicates the return type of the function • ( ) any input to the function would normally go here • empty parenthesis indicate that no special information is being passed to the function by the operating system Professor John Carelli int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; // Convert the distance to kilometers. kms = km_per_mile * miles; // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; return 0; } // end of main function Kutztown University Source: Pearson Education, Inc.

Types of Statements • All C++ statements end with “; ” • A single statement may span multiple lines • Two main types of statements • Declaration statements • describe the data the function needs: const float KM_PER_MILE = 1. 609; /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; float miles, kms; (note: this is all one line!) // Convert the distance to kilometers. kms = km_per_mile * miles; • Executable statements • specify actions the program will take cout << “Enter the distance in miles: “; cin >> miles; Professor John Carelli // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } return 0; Kutztown University Source: Pearson Education, Inc.

Reserved Words (Keywords) • Have special meaning in C++ • Cannot be used for other purposes /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; // Convert the distance to kilometers. kms = km_per_mile * miles; // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } Professor John Carelli return 0; Kutztown University Source: Pearson Education, Inc.

Identifiers • Names for data and objects (variables) to be manipulated by the program • Must begin with a letter or underscore (not recommended) • Consist only of letters, digits, and underscores • Cannot be reserved word • Upper and lower case significant /* miles. cpp - convert distance in miles to kilometers. */ #include <iostream> // class for stream input/output using namespace std; // use the standard namespace int main() // start of main function { const float km_per_mile = 1. 609; // 1. 609 km in a mile float miles= -1, // input: distance in miles kms; // output: dist in kilometers // Get the distance in miles. // Note: does not check if miles is valid!!! (i. e. >= 0) cout << "Enter the distance in miles: "; cin >> miles; // Convert the distance to kilometers. kms = km_per_mile * miles; // Output the distance in miles. cout << "The distance in miles is: " << miles << endl; • miles. cpp cin, cout, kms, km_per_mile, miles, std, endl Professor John Carelli // Output the distance in kilometers. cout << "The distance in kilometers is: " << kms << endl; } return 0; Kutztown University Source: Pearson Education, Inc.