Data, Variables and Expressions

Part:   1  2  3   4 

(Continued from previous part...)

Now let's review what have learned in this section with a sample program:

class Variables {
   public static void Main() {
      bool is_ok;
      int n;
      int num_of_sec; 
      long number_of_sec_in_a_year;
      float sqrt_s;
      double sqrt_d;
      char c1, c2, c3;
      char cr, cn;
      
      is_ok = true;
      num_of_sec = 86400;
      number_of_sec_in_a_year = 30458700;
      sqrt_s = 1.4142F;
      sqrt_d = 1.4142135623730950488016887242097;
      c1 = 'a';
      c2 = 'A';
      c3 = '0';
      cr = '\r';
      cn = '\n';

      n = 1;
      System.Console.WriteLine("Value of is_ok = {0}.", is_ok);
      System.Console.WriteLine("1 day = {0} seconds.", num_of_sec);
      System.Console.WriteLine("1 year = {0} seconds.", 
         number_of_sec_in_a_year);
      System.Console.WriteLine("Square root of 2 (float) = {0}.",sqrt_s);
      System.Console.WriteLine("Square root of 2 (double) = {0}.", 
         sqrt_d);
      System.Console.WriteLine("Some regular characters: {0}, {1}, {2}.",
         c1, c2, c3);
      System.Console.WriteLine("The return character: {0}.", cr);
      System.Console.WriteLine("The new line character: {0}.", cn); 
      n = 9;
      System.Console.WriteLine("WriteLine() is used {0} times.", n);
   }
}

Output of the program will be:

Value of is_ok = True.
1 day = 86400 seconds.
1 year = 30458700 seconds.
Square root of 2 (float) = 1.4142.
Square root of 2 (double) = 1.4142135623731.
Some regular characters: a, A, 0.
.he return character:
The new line character:
.
WriteLine() is used 9 times.

Observations from this program:

• Suffix 'F' is used in literal "1.4142", because real literals are considered to be of 64-bit size, which requires variable type "double" to hold the value. The suffix 'F' is forcing a real literal to be of 32-bit size.
• Literal "1.4142135623730950488016887242097" gets truncated and rounded to "1.4142135623731" during the execution of the assignment statement, because the double variable name sqrt_d can only hold about 14 decimal digits.
• Variable "n" gets assigned twice in the program. Variables can be assigned to new values many times.

Advice: Avoid using "int" and "float". Use "long" and "double" instead. In the old days, 32-bit data requires less memory to store and computer time to process than 64-bit data. This is not totally true now, because today's computers are designed to store and process data 64 bits at a time, not 32 bits at a time.

Expressions

So far we have learned how to enter data, store data, and retrieve data. The next step is to learn how to operate data, like how to add two values together to get the sum. This requires the help of data operations. Let's start with arithmetic operations first. Other types of operations will be discussed in later chapters.

There are 4 basic arithmetic operations that we can perform on integral and real data. Each of them is represented by special symbol called operator. Bellow is the operators of the 4 arithmetic operations:

• "*": Multiplication
• "/": Division
• "+": Addition
• "-": Subtraction

A single arithmetic operation can be entered into C# statements in a format called arithmetic expression, with the following syntax:

arithmetic_expression:
   literal arithmetic_operator literal

Note that the literals used in an arithmetic expression must be of the integral or real data type. For example: 1 + 2, 1.4142 * 1.4142, 10 / 3.

(Continued on next part...)

Part:   1  2  3   4