Course Logistics

What is this course about?

"How to program" is bigger than "C++" or any other language. Programming is a creative process, in which you construct a model world inside the computer that interacts with the real world via keyboards, mice, monitors, speakers network connections, and so forth. It's very rewarding and exciting; you will never be bored!

This course focuses on solid understanding of foundational concepts, so please be patient with the fact that your programs will usually be reading and writing text and not interacting with all the fancy peripherals mentioned above.

Words of Advice

The structure of a simple C++ program

#include <iostream>




using namespace std;





int main()
{
 
  cout << "The answer is ";
  cout << 7*6;
  cout << endl;



  return 0;
}

← This "includes" code needed to use the "standard library" iostream.
  Libraries are repositories of compiled C++ code that we can use in
  our own programs. iostream provides input/output functionality.

← This allows us to use shorter names for standard library  objects. 
  For example, without this line we have to  write "std::cout" rather
  than simply "cout".  The line is saying "just assume the 'std::'
  part".

← The "main" function.  For now, all our C++ code goes in between
  these { }'s.

← "cout << x" is how we write output.  The right-hand side can be 
  almost any expression. "std::cout" is the full name of the output
  stream associated with the terminal.  "cout << endl" sends a
  newline to the output stream.  

← A program actually returns a number to the command shell that
  launched it.  Returning 0 is like saying "this program exited
  normally".

Some more comments follow:

• In the early part of the course, the C++ statements in your program are listed between the { }'s in the body of the "main function".
• Usually there is one statement per line of the program. Each statement must end with a semicolon ";".
• These statements are executed one after the other from top to bottom.
• An object x can be printed to "standard out" using the syntax:

  cout << x

  The object x can be either a number or a string (a string is a sequence of characters). For short, you can print several things out in a single "cout" statement by separating them with "<<", like this:

  cout << "I am " << 44*12 + 3 << " months old!" << endl

• "endl" stands for end of line and produces a newline.

Compiled vs interpreted, and why C++ is different than Javascript

• Javascript is an interpreted language.
  This means that the code you write is read and processed by the browser, which then executes the steps demanded by that code.
• C++ is a compiled language.
  As shown in the figure below, this means that the code you write is read and processed by a special-purpose program called a compiler, which translates it into the zeros and ones that the CPU speaks, and stores it in an executable file. At some later point, the OS is told to start the program stored in the executable file running, and the CPU initiates its fetch-decode-execute cycle on the code contained in that file.

	Step 1: Source code writing. Use an editor to create the file hello.cpp containing the source code for the program.
$ g++ hello.cpp -o hello $	Step 2: Compilation. Use a compiler to translate the human-readable C++ source code into a binary (machine-readable), executable program hello. We will run the compiler by executing the left command on the terminal. In particular, g++ is a binary executable program that serves as a compiler. hello.cpp is the source code we wrote in Step 1. -o hello specifies the filename of the output binary program.
$ g++ hello.cpp -o hello $ ./hello Hello World! $	Step 3: Execution. Use the OS to initiate execution of (i.e. start the fetch-decode-execute cycle on) the program hello. In particular, Note that hello is the binary program that the compiler created in Step 2. To execute it, we prepend ./ (i.e., dot slash), which tells the terminal that the file is under the current directory. The binary program printed "Hello World!" just as we wanted!

All these steps are kind of a pain in the neck, but remember: we're writing a program that is executing on "bare metal", i.e. directly on the CPU.

Practice Problems

Do you know ...

http://xkcd.com/303/

• How are Javascript and C++ different?
• What are four steps you need to go through, when you write a program with the C++ programming language?