A Summary of Chapter 1

• Overall View
• Variables
• Arithmetic
• if statements
• Loops

Well, this is the end of Chapter 1 of the tutorial - and it's only taken me three weeks to write it. Here's a summary of what you really ought to know by now:

Overall View

• C++ programs are written in plain text files which are then translated into machine code ready for the computer to run. The program that translates them is called a compiler.

• Programs which intend to include input and/or output (which is all of them) should start with #include <iostream.h>.

• The main part of the program should start with void main (). The word void means that the program does not return a number to whatever called it (the Operating System, presumably). The word main means that this is the main part of the program. The () means that there are no parameters passed to the main program.

• The program consists of one or more instructions, called statements. The statements that make up the main part of the program are enclosed between { and }.

• It is possible to block statements together so that they can act as one statement. Statements are blocked using { and }. Any situation that requires one single statement can have a block of statements instead.

• Each statement ends with a semicolon.

• C++ is very tolerant of the layout of the program. The only place you can't put a new line or a space is in the middle of a keyword or a string constant.

• Things are printed on the screen using cout and are passed to cout using <<

• Comments are included either using //, in which case everything else on that line is the comment, or by including the comments between /* and */.

Variables

• Data can be stored in a program using variables. These are like small boxes in memory, each variable having a name, a contents and a data type.

• Variables must be given names consisting of letters, digits and/or underscore _.

• The name must not start with a digit but it can start with a letter or underscore.

• The three common types (there are others) are int, float and char, representing whole numbers (integers), decimal numbers (floating point numbers) and letters (or characters).

  int x;
  float height;
  char index_letter;
  int a,b,c;
  float mm, age;
  

• Variables must be declared before being used. This is done by putting either int, float or char followed the name(s) of one or more variables. If you are going to declare more than one variable in one line, then separate them with commas. Either way, the line should end with a semicolon, as any statement should.

• Three other types are double, which stores floating point decimal numbers to a higher precision than float, long which stores large positive or negative whole numbers, and unsigned int which is similar to int except that it can store higher numbers at the expense of negative whole numbers.

• Variables are assigned to values using =.

  my_try = 3;
  

• Alternatively, variables can be assigned during declaration:

  float step_value = 3.01;
  

• Or you can get the user to type in a variable value using cin >>.

Arithmetic

• Arithmetic is done using + (for addition), - (for subtraction), * (for multiplication), / (for division) or % (for the remainder when division is done).

• Be careful when you use / with integer variables - they will produce the whole number part of the division only!

• Multiplication and division are always done before addition and subtraction, unless brackets are put round the addition and subtraction to "promote" it:

  30 - 6 * 2 produces the value 18
  (30 - 6) * 2 produces the value 48

• You can put one set of brackets inside another:

  (2 * (3 + 4) - 7) % 2
  

if statements

• These test conditions to see whether they are true or not.

• If the condition is true, then one statement or block of statements is carried out.

• If the condition fails, there may be another statement or block of statements that executes (the else part).

• Conditions may include any of these operators:

  ==	Equal to
  !=	Not equal to
  >	Greater than
  <	Less than
  >=	Greater than or equal to (i.e. not less than)
  <=	Less than or equal to (i.e. not greater than)

• Simple conditions can be joined together to form compound conditions using && (for AND), || (for OR) and ! (for NOT).

Loops

• Loops are ways of repeating instructions many times without having to write them out many times.

• Loops can be performed a fixed number of times, or until some condition is met.

• There are three basic types of loop, the for loop, the while loop and the do ... while loop.

• The the for loop has this structure:

  for ( <initialisation>; <terminating condition>; <increment> )
      { one statement or block of statements }
  

  The the initialisation section tells the program what variable(s) to set up at the start of the loop. The the terminating condition is the condition which determines when the loop stops (the loop runs until the condition fails) and the the increment part indicates what the program is supposed to do at the end of each section - normally increasing or decreasing a counter value for the loop.

• The while loop has this structure:

  while ( <condition> )
       { one statement or a block of statements }
  

  The loop continues all the time that the condition is true. If the condition fails the first time round, the loop never executes.

• The do ... while loop has this structure:

  do
       { one statement or a block of statements }
  while ( <condition> );
  

  The loop continues all the time that the condition is true, but, unlike the while loop, the condition is tested at the end of each time round the loop. The statement(s) inside the loop are always executed at least once, as they have already been carried out when the condition is tested for the first time.

Crumbs, you have learned a lot, haven't you!

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