CIS-255 Home http://www.c-jump.com/bcc/c255c/c255syllabus.htm

C++ you already know

1. CIS-255 Object Oriented Programming in C++
2. C++ you already know
3. Stream I/O
4. Enumerations
5. User-defined types
6. Using existing classes
7. Adding functions to structs
8. A Bit of Advice
9. C++ Comments

Object Oriented Programming in C++

• Hello World

// My first C++ program
#include <iostream>
int main()
{
    std::cout << "Hello, World" << std::endl;
    return 0;
}

C++ you already know

• Control constructs: function calls,
  

  
  for, while, if, switch, etc.
  

• Native types
  

  
  int, float, double, char, void, bool b = true;
  

• Type modifiers

  
  int arr[100]; float* pf; unsigned char uch; long int num;
  
  

• Arrays and pointers:
  C++ uses specific dynamic allocation syntax

Stream I/O

• #include <iostream>

• std::cout, std::cin, std::cerr

  These correspond to stdout, stdin, and stderr in C
  
  
• The << and >> operators (a mixed blessing)

• std::endl

Enumerations

• keyword

  enum

enum Suit { CLUB, DIAMOND, HEART, SPADE };
Suit s; // enum keyword here not required
s = CLUB; // of course
s = (Suit) 1; // Ok, not recommended
s = 1; // ERROR
enum PrintFlags {COLOR=1, LANDSCAPE=2, TWOSIDE=4};
// Range is [0:7]
PrintFlags pf = COLOR | TWOSIDE;
pf = (PrintFlags) 6;
pf = (PrintFlags) 11; // Undefined!!
switch ( s ) { // use a default label!!

User-defined types

• keywords

  struct and class

  
  struct point { int x; int y; };
  point p1; // Note: struct keyword not needed
  p1.x = 9; // and so on...
  
  

• C++ structs and classes can also have functions

Using existing classes

#include <iostream>
#include <string>
using std::string;
int main()
{
    string s1 = "This is a string";
    std::cout
        << "There are "
        << s1.size()
        << " chars in "
        << s1
        << std::endl
        ;
    return 0;
}

Adding functions to structs

struct point {
    int x; // member variables
    int y;
    void adjust( int x_, int y_ ) // member function
    {
        x += x_;
        y += y_;
    }
}; // don't forget this semicolon

void main()
{
    // Now we can:
    point p;
    p.x = p.y = 4; // access to member variables
    p.adjust( 1, 1 ); // member function call
}

A Bit of Advice

• First, try being a client:
       use existing objects where possible.
  
  
• Second, design your own classes,
       but keep in mind the client perspective.

C++ Comments

• // comments from there to end of line
  
  
• /* */ works as in C
  
  
• Avoid mixing comments,
  since neither type respects the other:

  
  // this --> /* is not effective
  so this becomes an error */
  /* this --> // is not effective */ so this is an error
  
  

• Some compilers may give you a warning.