Hello World 2 What does all that mean?

The Evolution of Programming Languages Early computers programmed in machine language To calculate wages = rate * hours in machine language: 100100 010001 //Load 100110 010010 //Multiply 100010 010011 //Store

The Evolution of Programming Languages (cont’d.) Assembly language instructions are mnemonic Assembler: translates a program written in assembly language into machine language

The Evolution of Programming Languages (cont’d.) High-level languages Express algorithms at a more abstract level: int wages = rate * hours; Ex: Basic, FORTRAN, COBOL, Pascal, C, C++, C#, and Java http://oreilly.com/news/graphics/prog_lang_poster.pdf http://www.digibarn.com/collections/posters/tongues/tongues.jpg Current popularities http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

The Evolution of Programming Languages (cont’d.) Compiler: translates a program written in a high-level language into machine language

Processing a C++ Program (cont’d.) To execute a C++ program: Create a text source program in C++ Preprocessor directives begin with # and are processed by the preprocessor Compiler: Checks that the program obeys the language rules Translates into machine language (object program)

Processing a C++ Program (cont’d.) To execute a C++ program (cont'd.): Linker: Combines object program with other programs provided by the SDK to create executable code Library: contains prewritten code you can use

How the code works: # : preprocessor directive Instructions to do before compiling Bring the code from the library iostream into this file

How the code works: Use all the names that are in the "standard" grouping in my program Alternative:

How the code works: ; statement terminator Ends a "sentence of code"

How the code works: int main() The starting point of our program Program instructions go inside { }

How the code works: Comment : computer ignores // : rest of line is comment /* : everything is comment until */ /** : special comment – machine readable

Documentation Every file should have comment like this at top:

How the code works: cout : console output

How the code works: cout : console output << "send to output"

How the code works: cout : console output << "send to output" "Hello" : a string – piece of text

How the code works: cout : console output << "send to output" "Hello" : a string – piece of text endl : symbol representing "end of line"

How the code works: return 0 Program ran successfully Anything BUT 0 indicates error

Working with numbers We can output numbers to console: Can do math using + - / * Division may give interesting results…

Everything Counts Indentation & Style matter (to humans) Spelling & Capitalization matter (to humans & computers)