Introduction to C, C++, Java
P.J. Drongowski
15 September 2004

Some history
  + C
    - Dennis Ritchie
    - Bell Laboratories 1972
    - Predecessors: B (developed by Ken Thompson) and BCPL
    - Ken Thompson wanted to create computing environment -- led to UNIX
    - The C Programming Language: Brian Kernighan and Dennis Ritchie
    - Language was standardized in the mid-1980's (X3J11)
    - http://cm.bell-labs.com/cm/cs/who/dmr/chist.html
  + C++
    - Bjarne Sroustrup
    - AT&T Bell Laboratories 1983-1985
    - First called "C with Classes"
    - Inspired by object-orientation in Simula67
    - Stronger type checking than C
    - Was initially implemented as a C++ to C translator
    - Standardized (ISO/IEC 14882)
  + Java
    - Origins began in project at BridgeSystems; delivered to Sun in 1991
    - "Industrial strength Smalltalk written in C++"
    - Java is *not* Smalltalk
    - Team at Sun began development on Oak interpreter, leading to Java
    - May 1995 Sun publically announces Java
    - Bill Joy and Jim Gosling (Sun Microsystems)
    - Eliminate warts from C++, "run anywhere," security features (most
      importantly, references instead of pointers/addresses and no applet
        input/output)

We will use C strings in this course
  + Why?
    - C strings are in general use everywhere; all programmers know C strings
    - C++ strings are supported through a library
    - C strings are supported by just a handful of library routines -- easy
      to learn
    - C++ string library has many functions -- more difficult to learn
  + What is a C string?
    - A one-dimensional array of characters
    - Indexed from zero like all C arrays
    - String is usually terminated by a null (zero) character
  + C is a dangerous language
    - What happens when a string is overrun?
    - Security issue: buffer overrun vulnerability
    - Cracker sends message that overruns a string array on the execution
      stack with the intention of overwriting the return address
    - Program transfers control to another part of message holding the
      infectious payload
    - Always check array bounds!

/*
 * A fun C++ example using inheritance ("one from the crypt" :-)
 */

#include <iostream>
using namespace std ;

class Register {
private:
  unsigned int value ;
public:
  Register() { value = 0 ; }
  void clear() { value = 0 ; }
  void load(int newValue) { value = newValue ; }
  unsigned int read() { return(value) ; }
} ;

class Counter : public Register {
public:
  void increment() { load(read() + 1) ; }
  void decrement() { load(read() - 1) ; }
} ;

class ShiftRegister : public Register {
public:
  void left() { load(read() << 1) ; }
  void right() { load(read() >> 1) ; }
} ;

int main(int argc, char *argv[])
{
  Register ir ;
  Counter pc ;
  ShiftRegister ac ;

  pc.clear() ;
  pc.increment() ;
  pc.increment() ;
  ac.load(0x80) ;
  ac.right() ;

  cout << "pc: " << pc.read() << endl ;
  cout << "ac: " << hex << ac.read() << endl ;
}