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C++ This slide show introduces C++ & compares it to C. Vocabulary: attribute bool cin cout encapsulation iostream method namespace object oriented private public string w_char Christine S. Wolfe Ohio University Lancaster 2008-Aug-01

C appeared in 1972. It was developed by Dennis Ritchie at Bell Labs. In 1979, Bjarn Stroustrup at Bell Labs became interested in adding classes to C and overcoming some of the common problems with C. His additions were adopted in 1983 as C++. C++ was first standardized in 1998.

C++ is a superset of C. C++ C

The name: BCPl (Basic Combined Programming Language) …evolved into a language nicknamed “B” Dennis Ritchie adopted parts of B into his new language. Because it was a successor to B, he called it C. Bjarne Stoustrup extended the C language to invent C++ He coined the name C++ to imitate the increment operator (++) adapted from Dale. Weems. “Programming and Problem Solving with C++)

C++ supports (but does not require) object-oriented programming The main objects are in the std namespace and the line using namespace std; appears after the last #include statement

C++ includes two additional data types C Fundamental Data Types void char int float double C++ Fundamental Data Types void char int float double bool wchar_t

Differences: Standard I/O C++ #include <iostream> #include <iomanip> cout cin C #include <stdio.h> printf scanf printf(“The answer is %d\n”, Result); cout << “The answer is “ << Result <<endl; cin >> Rate; scanf(“\n%f”, &Rate) cout <<setw(8) << setprecision(4) << my_float; printf(“%8.4f“, my_float);

C++ provides a robust string header that includes a string data type. C Code #include <stdio.h> #include <string.h> int main () { char FirstName[25]; strcpy(FirstName, “Oscar”); return 0; } C++ Code #include <iostream> #include <string> using namespace std; int main () { string FirstName; FirstName = “Oscar”; return 0; }

C vs C++ Comparison of the Hello World program /* my first program in C */ #include <stdio.h> int main () { printf("Hello World!“); return 0; } // my first program in C++ #include <iostream> using namespace std; int main () { cout << "Hello World!"; return 0; }

C and C++ use the same arithmetic operators: + - * / % C and C++ use the same unary operators: ++ -- - C and C++ use the same logical operators: ! && || C and C++ use the same comparison operators: == < <= > >= != C and C++ use the same assignment operators: = *= /= %= += -=

C vs C++ keyboard input #include <iostream> #include <iomanip.h> #include <stdio.h> scanf(“\n %d”, &x); cin >> x;

In C, the programmer can define a new data type based on the fundamental types. The new data type is called a structure and is declared using the struct keyword. Inside the structure, attributes are defined based on existing data types. struct TestScore { char Pnumber[8]; int TestNum; float score; }; Variables can now be declared as type TestScore. data types variable names int Age; float Salary; TestScore StudentIn;

C++ expands the structure to include both the data (attributes) and functions (methods). A class is an expanded concept of a data structure: instead of holding only data, it can hold both data and functions. http://cplusplus.com The concept that all the attributes and behaviors of an entity are bound together in a single class is called Encapsulation class Cat { public: int GetAge(void); void SetAge(int age); void Meow(void); private: int itsAge; } ;

When a language supports the use of classes/objects, it is referred to as object-oriented. Procedure oriented programming the traditional programming that is based on algorithms or a logical step-by-step process for solving a problem. http://www.pcai.com/web/glossary/pcai_p_s_glossary.html Object oriented programming a class of programming languages and techniques based on the concept of an “object” which is a data structure encapsulated with a set of routines which operate on the data. C++ and Java are object oriented programs http://www.powerhousemuseum.com/hsc/lexicon/glossary.htm

Classes are diagrammed as shown below. class name Cat attributes itsAge GetAge(void); SetAge(int age); Meow(void); methods

An object is an instantiation of a class. In terms of variables, a class would be the type, and an object would be the variable. class Cat { public: int GetAge(void); void SetAge(int age); void Meow(void); private: int itsAge; } ; class object int Age; float Salary; TestScore StudentIn; Cat Puff;

Each method must be defined. Methods are defined in the same manner as a subfunction. The name of the method is justified by the prepending the class name + :: class Cat { public: int GetAge(void); void SetAge(int age); void Meow(void); private: int itsAge; } ; void Cat::SetAge(int age) { itsAge = age; } method prototype method definition

When calling a method, or referring to an attribute of the class, prepend the OBJECT name (not the class name) and a period to the method or attribute. class Cat { public: int GetAge(void); void SetAge(int age); void Meow(void); private: int itsAge; } ; int main() { Cat Frisky; int Years; int YearCtr; printf("\nPlease enter Frisky's age "); fflush(stdin); scanf("\n%d", &Years); Frisky.SetAge(Years); cout << "Frisky is a cat who is "; cout << Frisky.GetAge() << " years old.\n"; for(YearCtr = 1; YearCtr <= Years; ++YearCtr) { Frisky.Meow(); } printf("\n\n\n\n"); return 0; }

Differences: String class C #include <string.h> …for C-strings C++ #include <cstring> …for C-strings #include <string> …for string class A C-string is an array of chars terminated with NULL A class string is an object and has methods that can be used to manipulate the string. By default, a literal such as “Ohio University” is a C-string.

Declaring strings C-strings are declared and manipulated as in C string class objects are declared as type string string FirstName; string Greeting = “Hello”; A string declared as type string can... use the assignment operator FirstName = “Jane”; use the + operator Greeting = Greeting + “ “ + Firstname (note, at least one of the operands must be a string class object) use string methods FirstName.substr etc use comparison operators == != < <= >= > (watch out for upper/lower case)

C++ cin >> >> (extraction operator) extracts desired data value from the input stream skips any leading whitespace characters if data value is a char >> extracts exactly 1 character if data value is an int >> extracts characters until first inappropriate character if data value is a float >> extracts characters until first inappropriate character if data value is a string >> extracts characters until first whitespace Examples: (given: i & j are ints, x is float, ch is char, str is a string) Statement Data Result cin >> I; 32 cin >> i >> j; 4 60 cin >> i >> ch >> x; 25 A 16.9 cin >> i >> ch >> x; 25A16.9 cin >> i >> j >> x; 12 8 cin >> i >> x; 46 32.4 15 cin >> str; Jane cin >> str; Jane Doe

C++ • Drawbacks to the >> operator when inputting strings • If string isn’t large enough, the >> operator will continue to store characters into memory beyond the end of the array. • The >> operator cannot be used to input strings with embedded whitespace.

Solution cin.get() (assume ch is a char and str is a string and n is an int) get() does not skip leading whitespace cin.get(ch ); reads a single character (even a whitespace) cin.get(str, n); reads up to n-1 chars & appends ‘\0’ stops at newline, or n-1 chars newline left in stream cin.get(str, n , delimiter) reads up to n-1 chars & appends ‘\0’ stops at delimiter, or n-1 chars delimiter left in stream getline(cin, str) reads entire line up to ‘ \n’ extracts newline from stream and stores

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