Fundamentals of Programming using C++

In general, a C++ program has five zones (or sections). If you viewed a complete program through the wrong end of a pair of binoculars, you would see these sections as shown in the following list:

Section 1: Introductory comments

These contain the name of the author, the date the program was written, the main purpose of the program and any important assumptions made by the programmer. These are recommended in all your programs and are part of the culture of 'good' programming.

Section 2.: Included header files

These statements tell the compiler what auxilary files to process before processing the actual program. Usually the files contain useful functions (sub programs) that have been pre-written. You will need to include at least one header file even in your first program. Later you will learn to include several different header files.

Section 3: Function prototypes

These are the first line (only) of the separate functions (sub-programs or modules) the programmer has designed as part of the solution. They are used to 'introduce' the names of all the functions the program uses. Your early programs will not contain any subprograms so you don't have to worry about this section just yet.

Section 4: The Main function

This is the main section or "main block" of the program. It controls the activities of all the subprograms and usually encapsulates the general logic used to solve the given problem. All your programs will have a main block.

Section 5: Function definitions

This is the actual detailed description of each and every function (subprogram) used in your program. You won't be using functions at all in the early stages.

Don't be concerned if this sample program appears complex. The ones you will be expected to write in the early stages of this course will be much simpler. However you may well be able to figure out what the sample program does. So, as well as checking for the five sections, try to interpret what the programmer is doing - make intelligent guesses!

// Section 1: (Introductory Comments)
// A sample program showing the
// overall structure of non-OOP, C++ programs
// Author's Name...
// Date created ..
// Compiler used...

// Section 2: (Included files)
#include <iostream.h>

// Section 3: (Function prototypes)
float calc_average( int n1, int n2, int n3 );

// Section 4: (The main function)
void main( void )
{
  int first, second, third;
  float result;

  cout << "Please enter three whole numbers separated by spaces";
  cin >> first >> second >> third;
  result = calc_average( first, second, third );
  cout << "The average of the numbers is " << result << endl;
}

// Section 5: (Function definitions)
float calc_average( int n1, int n2, int n3 )
{
  float answer;
  answer = (float) (n1 + n2 + n3 ) / 3;
  return answer;
}

1. Look firstly at section 4 of the sample program. This is the main function. The main function in a C++ program encapsulates the overall logic of the program. Try to recognise the main tasks done by this program.

2. The word float is used to describe floating point numbers. Can you guess what the word int describes?

Author:

Errol Chopping

Lecturer in Computing

Charles Sturt University - Mitchell

Bathurst NSW 2795

Australia.

Last Update: Nov 17, 1995