Elements of a C++ Program

• Every C++ program looks something like:

  #include <iostream>
  
  using namespace std;
  
  int Square(int n);
  int Cube(int n);
  
  int main () {
      cout << "The square of 27 is " << Square(27) << endl;
      cout << "The cube of 27 is " << Cube(27) << endl;
  
      return 0;
  }
  
  int Square (int n) {
      return n*n;
  }
  
  int Cube (int n)  {
      return n*n*n;
  }
     

• Square and Cube are functions, or subroutines
• The program
  • Prints "The square of 27 is"
  • Calls the square routine
  • Prints 27 squared
  • Prints the end of line marker
  • Prints "The cube of 27 is "
  • Calls the cube routine
  • Prints 27 cubed
  • Prints the end of line marker
  • Exits.
• SYNTAX is how to construct a statement
  • ie, most of them end in ;
• There is also SEMATICS
  • cout << " The Square of 27 is " << Square(72) << endl;
• They introduce metalanguages
  • identifier = alpha | alpha alpha-or-digitsequence
  • alpha-or-digit-sequence = alpha-or-digit | alpha-or-digit alpha-or-digitsequence
  • alpha-or-digit = alpha | digit
  • alpha = a|b|c|...z|A|B|C|...Z
  • digit = 0|1|2|...|9
• Gives us a way to specify things.
• They also discuss syntax templates.
  • You should look these over LATER
• Every program must have a main routine

  int main() {
      
      return(0);
  }
     

• Identifiers
  • We will use identifiers throughout the our programs
  • Square, Cube are both identifiers
  • There are some rules for constructing them
    • You must start with a letter
    • They may contain letters and numbers, and some special symbols
    • But not +,-,*,&,|,....
    • May not be a reserved work (just a min)
  • Some bad examples
    • 40days - must start with alpha
    • Hello There - no space
    • day+night - no +
    • main - reserved word
• Reserved Words are words with special meaning in C++
  • We will be learning these as the semester goes along
  • main is a reserved word
  • cout, endl, include
• How to make a good identifier
  • It should have a meaning. (foo is bad, TotalNumberOfStudents is good)
  • It should be a mix of upper and lower case (TOTALSUM is bad, HoursWorked is good)
• DATA
  • We will mostly be concerned about manipulating data
  • We will have a number of types of data that we will work with.
  • A data type is a specific set of data values along with a set of operations on those values
  • Think letters, integers, real numbers, ...
  • Data is stored in memory
  • Different data types take different amounts of memory
• Character data types
  • To declare (or make space in memory to store one)

    char identifier ;
           

  • for example

    char MiddleInitial;
           

  • or

    char identifier, identifier, ... identifier ;
           

  • for example

    char FirstInitial, MiddleInitial, LastInitial, ch;
           

  • They can hold any single character from the ASCII character set
  • For example:

    'a', 'A', '+' '_' '4' ...
           

  • When we want to stick a value intom memory, we use an assignment statement, and the character constant must be in ''

    MiddleInitial = 'M';
    FirstInitial = 'D';
    LastInitial = 'B';
    

  • There is much more we can do with them, but this will do to start.
  • Here is an example