Basics of C++

• We will discuss the basics of a c++ program.
• Unfortunately this is not part of your book.
• There are numerous on-line resources however.
  • I will point to some of these as we go.
• Basic program structure
  • Not all of this is required,
  • We will discuss most of these parts in turn.
  • But some will not be discussed in detail until much later.
  • but for now please use the following shell

  • #include <iostream>
    
    using namespace std;
    
    int main() {
    
        return 0;
    }

• Note this structure contains some style conventions as well.
  • Whitespace
    • We generally put one statement per line.
    • We generally blank lines to separate different ideas.
    • We generally indent inside of {} blocks.
    • For more information see the local guide.
  • Whitespace in statements
    • Generally separate everything with one space.
    • Inside braces, indent four spaces per bracket.
  • Placing brackets
    • There are multiple ways you can place brackets.
    • I like this way (K&R)

    • int main() {
           code indented
      } 

    • Others like this (Allman)

    • int main()
      {
          code indented
      }

    • Pick one of these and stick with it.
• #include <iostream>
  • In c++ this is a preprocessor directive.
    • The preprocessor gets code ready for the compiler.
    • In this case we are asking to include code from the iostream library.
    • A library is a set of auxiliary routines that are not part of the core programming language.
    • g++ -E shell.cpp
    • Notice that this produces c++ code.
      • But it is 36000 lines long!
  • Why is I/O in a library?
    • I/O tends to be different for each OS and each architecture.
    • Specifying it in a library allows the language to be more portable.
  • A list of c++ preprocessor directives can be found here.
  • The syntax for include can be found here.
  • We will discuss iostream in detail soon.
  • Note, it does not end in a ; because it is not a c++ statement.
  • Later we will include other things, and we might not even include iostrem, but please include it for now.
  • Wow, only one statement!
• using namespace std;
  • using and namespace are reserved or keywords in c++
  • See this reference for a full list of the current keywords.
  • Namespaces are somewhat complex and we will hold off full discussion until OOP.
  • But right now, we have multiple people with the same name.
    • In my wife's family is Dan Bennett and Dan Blackman.
    • To distinguish we use namespace bennett means all calls to Dan refers to me.
    • use the full name Dan_Blackman to get to the other Dan.
  • The word std
    • Refers to the standard namespace.
    • In this case, it is the "standard" library, part of which was included above.
    • This is a standard identifier (unfortunately the word standard means different items here).
  • Later we might not use this statement, but for now put it in please.
• int main () { }
  • This tells the compiler which code we wish to execute first.
  • main is a standard identifier.
    • Compilers build the program so it starts executing the code in main.
    • main is a function.
    • In c++ functions can take parameters inside the ()
      • In this case it does not.
      • Later we will discuss how to pass parameters.
    • In c++ functions potentially return a value
      • In this case it returns a integer.
  • int is a reserved word
    • It means the integer type.
    • In this case, main will return an integer.
  • { } is a codeblock.
    • This groups multiple statements into a single statement.
    • It is required for main.
    • We indent code inside of a code block.
• return 0;
  • This is really the only executable statement in the program.
  • return is a reserved word.
  • It says to return from the current function.
  • In this case it transfers control back from the function main to the operating system.
  • 0 is an literal constant.
    • Literal because it is literally in the code.
    • Constant because it is a non-changeable value.