BSM550 C Programming Language

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1 BSM550 C Programming Language Major Differences between C and C++ Prof. Manar Mohaisen Department of EEC Engineering

2 Lecture Objectives v Discover The major differences between C and C++ languages v Make your way To master C++ language It is the perfect time! 2

3 General Differences v Level C is regarded a low-level language Access to machine hardware Not user friendly and has a difficult interpretation C++ is middle-level language Has properties of low-level (as before) and high-level languages (concentrate on the program) v Security Data is not secured in C while the data is secured in C++. v Building blocks C is function-driven language C++ is object-driven language (object of a class) 3

4 General Differences v NAMESPACE C does not have the namespace feature while C++ has Namespace: This feature avoids name collision of identifiers v Standard input and output C language uses the header <stdio.h> with functions scanf and printf C++ language uses the header <iostream.h> with functions cin>> and cout<< <stdio.h> is included in <iostream.h> v File input/output C++ language uses the header <fstream.h> with the << and >> directives 4

5 Function Overloading v Function overloading C++ supports function overloading while C does not. Two or more functions can have the same name with the help of Polymorphism # include <stdlib.h> // 3 different functions having the same name double add(double, double); int add(int a, int b); void add(int *a, int b); void main() int ii = -3, jj = 5, kk = 0; double a = 5, b = 6, c = 0; c = add(a, b); kk = add(ii, jj); add(&ii, jj); double add(double a, double b) return(a + b); int add(int a, int b) return(a + b); void add(int &a, int b) (*a += b); 5

6 Dynamic Memory Management v Memory allocation C: calloc(), malloc() C++: new v Memory release C: free() C++: delete v Both Use the NULL # include <stdlib.h> void main() int ii = 0, jj = 0; int **in, N = 10; in = new int * [N]; for(ii = 0; ii < N; ii++) in[ii] = new int [N]; for(ii = 0; ii < N; ii++) for(jj = 0; jj < N; jj++) in[ii][jj] = rand() % 11-5; for(ii = 0; ii < N; ii++) delete [] in[ii]; in[ii] = NULL; delete [] in; in = NULL; 6

7 File Input / Output v C++ language It uses the header file <fstream.h> # include <fstream.h> void main() long start, end; ofstream fileout; // out file stream ifstream filein; // in file stream fileout.open("myfile.txt", ios::out); // open a file for writing if(fileout.is_open()) fileout<<"i am a student."; fileout.close(); filein.open("myfile.txt", ios::in); // open a file for reading start = filein.tellg(); // current location filein.seekg(0, ios::end); // move to end of file end = filein.tellg(); cout<<"the size of file is "<<(end - start) <<"Bytes"<<endl; filein.close(); 7

8 Structure in C++ v In C++ language Structures can have functions v In C language This feature is absent void main() struct COMPLEX cvar = 4, 8, result; double powv; powv = cvar.power(); cout<<powv<<endl; result = cvar.cconj(); cout<<result.real<<"\t"<<result.imag<<endl; # include <stdlib.h> struct COMPLEX double real; double imag; // function dec/def inside a structure double power() return(real*real + imag*imag); //another function dec/def COMPLEX Cconj() struct COMPLEX out = real, -imag; return out; ; 8

9 Structure in C++ v In C++ language Structures can have functions v In C language This feature is absent void main() struct Complex cvar = 4, 8, result; double powv; powv = cvar.power(); cout<<powv<<endl; result = cvar.cconj(); cout<<result.real<<"\t"<<result.imag<<endl; # include <stdlib.h> struct Complex double real; double imag; // function inside a structure Complex Cconj; double power(); ; Complex Complex::Cconj() struct Complex out = real, -imag; return out; double Complex::power() return(real*real + imag*imag); 9

10 Operator Overloading v C++ language Supports operator overloading while C language does not. # include <stdlib.h> struct Complex double real; double imag; // the product (*) overloading Complex operator*(const Complex &in2) const; ; void main() struct Complex in1 = 2, 3, in2 = 1, -1, in3 = 0, 0; in3 = in1 * in2; // overloaded * cout<<in3.real<<"\t"<<in3.imag<<endl; Complex Complex::operator*(const Complex &in2) const struct Complex out; out.real = real * in2.real - imag * in2.imag; out.imag = real * in2.imag + imag * in2.real; return out; 10

11 Operator Overloading v Combining Operator and function overloading # include <stdlib.h> struct Complex double real; double imag; Complex operator/(double a); // define this function Complex operator/(struct Complex *in1); ; void main() struct Complex in1 = 2, 3, in2 = 1, -1, in3 = 0, 0; Complex Complex::operator/(double a) struct Complex out; out.real = real / a; out.imag = imag / a; return out; in3 = in1 / in2; // overloaded / in1 = in1 / 3.; // overloaded / 11

12 Classes v Presence C++ language has classes while C does not have. # include <stdlib.h> class ComplexC private: //default type double * cvector; public: double real; double imag; double initiate(); ; void main() ComplexC cnum1; cnum1.cvector = new double [5]; // WRONG cnum1.initiate(); void ComplexC::initiate() real = imag = 0.; // possible cvector = new double [10]; private: [default access specifier] Accessible only by other members of the class or from their friends public: Accessible from anywhere the object is visible. protected: Same as private + that they are accessible from members of their derived classes. 12

13 Classes v Constructor It is used to initiate an object of a class It has the same name of the class but might have arguments v Destructor It is used to delete an object It has the same name class proceeded by ~ # include <stdlib.h> class ComplexC public: double real; double imag; ComplexC(); ComplexC(double a, double b); ~ComplexC(); // constructor overloading ; void main() ComplexC cnum1; ComplexC cnum2(3, 5); ComplexC::ComplexC(double a, double b) real = a; imag = b; ComplexC::ComplexC() real = imag = 0; ComplexC::~ComplexC() 13

14 Classes v Friendship # include <stdlib.h> # include <math.h> class ComplexEx; class ComplexC private: double real; double imag; public: ComplexC polar2rect(complexex in); ; class ComplexEx private: double angle; double value; public: void set(double a, double b) angle = a; value = b; friend class ComplexC; ; void main() ComplexEx cex; ComplexC cnum; cex.set(5, ); cnum.polar2rect(cex); ComplexC ComplexC::polar2rect(ComplexEx in) (*this).real = in.value * cos(in.angle); (*this).imag = in.value * sin(in.angle); return(*this); 14

15 Classes v Inheritance The possibility to create classes derived from other classes The new classes include some of its parents members, plus its own. Format of declaring a derived class class derived_class_name : public parent_class_name Example Note that the derived class can t access the private members of the parent class. class ComplexC protected: double real; double imag; public: ComplexC rect2polar(complexex in); ; class ComplexEx : public ComplexC private: double angle; double value; ; 15

16 Classes v Inheritance Note that: Derived classes can only access protected and public members of the father class. class derived_class_name : public parent_class_name The access specifier public indicates the most accessible level the inherited members will have. Then, protected members will be inherited as protected members public members will be inherited as public members class derived_class_name : protected parent_class_name All inherited members will become protected in the derived class. class derived_class_name : private parent_class_name All inherited members will become private in the derived class. 16

17 Classes v Inheritance Multiple inheritance class derived_class : public parent_class_1, public parent_class_2/* */ Default access level is private class derived_class : parent_class /* */ This is equivalent to class derived_class : private parent_class /* */ More topics Have fun discovering them by yourself! 17

18 Q&A v Discussions v General remarks on this course 18

C Programming Language

Department of Electrical, Electronics, and Communication Engineering C Programming Language Storage Classes, Linkage, and Memory Management Manar Mohaisen Office: F208 Email: manar.subhi@kut.ac.kr Department