Program Structure

1
Program Structure
2
Hello World
Description of the program
filename

• /
  
• HELLO.CPP
• Author Adrian Chan
• Student ID 100123456
• This program is a simple program that displays
  Hello World.
• Modifications
• 08/08/07 AC First created.
• 
  /
• include ltiostreamgt
• using namespace std
• int main()
• cout ltlt "Hello world!" ltlt endl // Display
  message

Name and student ID
List of modification. Date, (yy/mm/dd), initials
of who modified the file, and comment on the
modification. In this course, since you are not
problem going to do any modifications once the
program it working, it will just have one line as
shown here.
Program comment header
3
Comments

• Programmers use comments in their code to provide
  information to the reader on what the code is
  doing. When a program is compiled, the compiler
  simply skips all comments. It is common (and
  good) practice to use a comment at the top of the
  code containing general information about the
  file, which is known as the header information.
• A comment is indicated using the deliminators /
  and /. An alternative syntax is available for
  single line comments using a //. This indicates
  that the text following the // on this line is a
  comment. An end deliminator is not needed in this
  case.

4
include

• The include directive tells the compiler that
  additional features are required in this program,
  which are not part of this file. In hello.cpp we
  have the directive
• include ltiostreamgt
• The compiler knows that it must also use the
  features that are specified in the library
  iostream. By including iostream in hello.cpp we
  are able to use the cout feature to display our
  messages.
• Commonly used library files and examples of their
  features
• iostream cin, cout
• cmath pow(), exp(), sin(), sqrt()
• cstdlib rand(), qsort(), getcwd()

5
main

• int main() specifies the name of a function
  called main. C programs begin their execution
  by calling the main function. Functions are
  specified using the following syntax
• ltoutput parametersgt ltfunction namegt(ltinput
  parametersgt)
• For the purposes of this course, the main
  function will always be specified as int main().
  This means it has no inputs from the operating
  system, hence nothing specified in the
  parentheses. It also means the main function will
  be returning an integer to the operating system
  this will be discussed at a later slide.
• The contents of a function are deliminated by
  and .

6
cout

• A simple way of displaying information on the
  monitor is using cout. The code
• cout ltlt "Hello world!" ltlt endl
• displays Hello world! on the monitor followed by
  an end of line character (similar to a Carriage
  Return key on a typewriter it brings the cursor
  to the beginning of the next line). Text is
  deliminated using quotation marks "". The ltlt
  operator is used to indicate successive inputs to
  cout.

7
semicolon

• The semicolon at the end of the cout statement is
  used as a statement terminator. Each individual
  statement must be ended with a semicolon. This
  concept is similar to a period in the English
  language, which is used to terminate each
  sentence.

8
System Pause

• The system("pause") is used to have the program
  output
• Press any key to continue . . .
• which will wait for the user to press a key to
  continue the execution of the program. It is used
  at the end of a program to stop the output window
  from closing before one is able to read the
  contents of the output window.

9
Return

• The return statement is used to return a value
  from a function. When the return statement is
  encountered, the function will exit. In the case
  of the main function, the program will stop
  (exiting the main function is equivalent to
  stopping the program). A return statement can
  return at most one value.
• For the main function, the return statement will
  be returning an integer value back to the
  operating system. This value will not be used for
  any purpose in this course. If the program
  terminates with no errors occurring, we will
  typically return a value of 0. If an error in the
  program does occur (e.g. cannot open an input
  file causing the program to terminate early) the
  program will return a non-zero value in this
  course we will typically just use a value of -1
  in such cases.

10
Code Formatting

• During compilation, white space (i.e. spaces,
  tabs, carriage returns) is ignored. The file
  hello.cpp could also be written as
• include ltiostreamgt
• using namespace stdint main()
• cout ltlt "Hello world!" ltlt endl // Display
  message
• system("pause")return 0
• It is the deliminators, including the semicolon,
  that the compiler uses to distinguish the
  components of the code.
• It should be readily apparent that the original
  code is much easier to read than the code shown
  on this slide. While the two programs function
  exactly the same, having properly formatted code
  helps to program efficiently, preventing mistakes
  and making it easier to track mistakes. Do not
  wait until your program is complete to format
  your code format properly as you create your
  code.

11
Problem 1 Hello world!!!
Write a program that displays the output shown
below.

• Hello world!!!
• This course is ECOR1606.
• This course is great!