C++ (intro) Created by Hwansoo Han Edited by Ikjun Yeom

Why New Languages?  Already know  C, Java, Python, Matlab, …  C++  Basically extension to C  All C code compiled with C++ compilers  But many libraries and “OO” concepts added 2

Many Use C++  Most recent open source projects  Written in C++ or Java  Easier to understand – “OO” design  Natural extension to C  C and C++ can be easily mixed (with a little efforts) 3

Hello, World! 4 /* * First program in C++ : hello world */ #include using namespace std; // main function int main() { cout << “hello, world!” << endl; return 0; } /* * First program in C++ : hello world */ #include using namespace std; // main function int main() { cout << “hello, world!” << endl; return 0; } console output

C++ IDE  Download Cygwin   Set PATH to include g++ or gcc ( 제어판 > 시스템및보안 > 시스템 > 고급시스템설정 > 고급 tab> 환경변수 )  Download JRE 6.0 or above  Google “JRE 64bit windows 7”  E.g. Downloads.cnet.com  Run the downloaded file to install JRE  Download Eclipse CDT (C/C++ development tooling)   Download “Eclipse IDE for C/C++ Developers”  Unzip the downloaded file into a directory  E.g. D:\bin\ 5

Genealogy of Programming Languages 6

C++ vs. C vs. Java: Minor Differences  Boolean type  C:int myBooleanValue = 1 ;  C++: bool myBooleanValue = true;  Java: boolean myBooleanValue = true;  Printing  C: printf(“Hello!\n”);  C++: cout << “Hello!” << endl;  Java: println(“Hello!”); 7

C++ vs. C vs. Java: Minor Differences  Calling other functions  C/C++ : define before use  Java : no such worries void PrintHello(); void PrintTime() { cout << “It’s time to go!” << endl; } int main() { PrintHello();// OK – Prototype defined earlier PrintTime();// OK – Function defined earlier SayHi();// ERROR – no prototype earlier } void PrintHello() { cout << “Hello!” << endl; } void SayHi() { cout << “Hi!” << endl; } void PrintHello(); void PrintTime() { cout << “It’s time to go!” << endl; } int main() { PrintHello();// OK – Prototype defined earlier PrintTime();// OK – Function defined earlier SayHi();// ERROR – no prototype earlier } void PrintHello() { cout << “Hello!” << endl; } void SayHi() { cout << “Hi!” << endl; } 8

C++ vs. C vs. Java: Major Differences 9  C/C++ has no garbage collector  Java :Integer myInt = new Integer(); myInt = NULL;// GC will delete  C++ : programmers need to delete  C : programmers need to free  Objects  Java : memory for all objects is put on the heap  C++ : Objects can be placed either on the stack or the heap  C : no objects, malloc gets the space from the heap

C++ vs. C vs. Java: Major Differences 10  C++ can choose to pass by value, pointer, and reference  C can choose to pass by value or pointer  Java cannot choose  Primitives only pass by value  Objects only pass by reference /* Java */ void AddOne(int x) { x++; } void run() { int x = 7; AddOne(x); println(x); // output 7 } /* Java */ void AddOne(int x) { x++; } void run() { int x = 7; AddOne(x); println(x); // output 7 } /* C++ */ void AddOne(int &x) { x++; } int main() { int x = 7; AddOne(x); cout << x << endl; // output 8 } /* C++ */ void AddOne(int &x) { x++; } int main() { int x = 7; AddOne(x); cout << x << endl; // output 8 } /* C */ void AddOne(int *x) { (*x)++; } int main() { int x = 7; AddOne(&x); printf(“%d\n”, x); // output 8 } /* C */ void AddOne(int *x) { (*x)++; } int main() { int x = 7; AddOne(&x); printf(“%d\n”, x); // output 8 }

Coding Style – Managing Large Code 11  Instead putting all into a single file, separate them for easier management  Files with extension.cpp/.cc contains implementations of functions  Files with extension.h contains function prototype .h files are used to overall shape of source code  Other programmers can roughly recognize your programs through header files (.h files)  If you don’t care the details on how a function works, you don’t have to look into.cpp files.

C++ vs. C vs. Java: Similarities 12  Short circuit evaluation  if (x < 4 || y == 3) // test the first (x<4), if true skip the second  Integer division  9/4 ⇒ 2  Primitives  char, short, int, long, float, double  Type conversion  3/2.0 ⇒ 1.5  ⇒ 18.2  Functions, objects (C++/Java), arithmetic operators, …