Understanding Data Types and Arithmetic Operators in Programming

1. Input & OutputStatement 01204111 Computer & Programming Group 350-352 Dept. of Computer Engineering Kasetsart University Adopted from Thanomkulabut’s experiences. Brushed up by MikeLab.Net Factory @KU. Version 2012

2. Review • Data Type • Arithmetic Operators • Math Class

3. Data Types

4. Priority of Arithmetic Operators high low

5. Arithmetic Arithmetic Operators Example • x/y*b++ • int a, b, c; • a = 2-10*3/5+(6%4); • b = 5*(15%4+(2-3))/9; • c = 5+9%2*4-14/4%3 Answer a = -2 b = 1 c = 9 2 3 Given x = 3.0, y = 2.0, b =2, what is the output? • x/y*++b • Answer: 4.5 • Answer: 3.0

6. Arithmetic Arithmetic Operators Example Answer int a=1, b=2, c=3; Console.WriteLine(a++ + ++b); Console.WriteLine(a++ - ++b); Console.WriteLine(++a + b++ + c++); Console.WriteLine(++a + b++ - c++); Console.WriteLine(++a - b++ - c++); 4 -2 7 1 -3 4, -2, 11, 6, -5

7. Arithmetic Operators Example(2) sum += x; // is equivalent to sum = sum + x prod *= 2.5; // is equivalent to prod =prod * 2.5 y -= 3+a; // is equivalent to y = y – (3+a)

8. Math Class The Math Class

9. Today’s Outline • Input Statements • Console.ReadLine() / Console.Read() • Basic Data Conversions • Output Statements • Console.Write() /Console.WriteLine() • Output format • Escape Sequences Characters • Data Conversions • Type of Conversions • Convert class, Parse() methods

10. Input Statements

11. Input Statements • Console.ReadLine(); • Read all characters (in form of string) • Use with Convert or Parse commands frequently • Console.Read(); • Read ASCII code of the first character

12. Console.ReadLine() • Console.ReadLine() • Use to get the input (String) from user • Convert string to other data type • int.Parse() Convert string to integer • double.Parse()  Convert string to double • …. stringst = Console.ReadLine(); Run-time error may be occurred if user’s input is incorrect

13. Console.ReadLine() Example Ex1: string myname; myname = Console.ReadLine(); Console.WriteLine(“Your name is {0}”, myname); Kun Toto Your name is Kun Toto Ex2: int x; Console.Write(“Input x:”); string temp = Console.ReadLine(); x= int.Parse(temp); x = x*x; Console.WriteLine(“x^2 = {0}”, x); Input x:12 X^2 = 144

14. Console.Read() • Console.Read returns an ACSII value (Integer) of the code of the first typed character. inti; Console.Write(“Input char:”); i = Console.Read(); Console.WriteLine(i); Input char: A 65

15. Output Statements

16. Output Statements • Console.Write(); • Show output • Console.WriteLine(); • Show output and shift to new line

17. Statement Output Statements • Use the method Write or WriteLine in the Console class (which is in System namespace) • Basic usage: • Advanced usage with formatting Console.WriteLine("Hello"); Console.WriteLine(area); Console.WriteLine(”Size {0}x{1}”, width, height); double salary=12000; Console.WriteLine("My salary is {0:f2}.", salary);

18. Basic Usage Console.Write(“Happy”); Console.Write(2009); Output : Happy2009 string Console.WriteLine(“Happy”); Console.WriteLine(2009); Output : integer Happy 2009

19. Advanced Usage int a=7, b=2; Console.WriteLine(“a={0} and b={1}”,a,b); Console.WriteLine(“{1}+{0}={2}”,b,a,a+b); a=7 and b=2 {0} {1} 7 + 2 = 9 {1} {0} {2}

20. Advanced Usage (2) 20

21. Advanced Usage (3) int a = 10; For a complete list of format specifiers, see http://msdn.microsoft.com/library/en-us/csref/html/vclrfFormattingNumericResultsTable.asp

22. Escape Sequences Characters • What should you do if you would like to write “C:\mydocument” Console.WriteLine(““C:\mydocument””); Console.WriteLine(“\“C:\mydocument\””); Console.WriteLine(“\“C:\\mydocument\””); 

23. Unicode Characters เกม 0e40 0e01 0e21 Console.Write(“\u0e40\u0e01\u0e21”); เกม Reference: http://unicode.org/charts/PDF/U0E00.pdf

24. Data Conversions

25. Data Conversions • In some situation we have to convert data from one type to another. • We may want to convert width and height of rectangle from Console.ReadLine() to int and calculate the rectangle area from the converted data. • Type of conversions • Widening conversions • Convert from a smaller data type to a larger one • Ex; int  double • Narrowing conversions • Convert from a larger data type to smaller one • Ex; double  int Losing some information!!!

26. Data Conversions (2) • Assignment conversion • Occurs automatically when a value of one type is assigned to a variable of another. • Ex: aFloatVar = anIntVar; • Arithmetic promotion • Occurs automatically • Ex: aFloatVar/anIntVar • Casting Value of anIntVar is converted to float data type automatically Value of aFloatVar/anIntVarisconverted to float (Larger data type)

27. Casting • Both widening and narrowing conversions can be accomplished by explicitly casting a value. • To cast, the type is put in parentheses in front of the value being converted. • Example • byte b, inti, long l • i = (int)b; l = (long)b + (long)i; int byte int long long

28. Casting (2) • Example • byte b; int i; long l; double d; • d = (double) i /10; • b = (byte) l +3; • i = (int) d – 10; int double double int 100% OK, but may yield unpredictable result in some case byte long OK, but may yield unpredictable result in some case

29. Convert.To<type>(); byte boy=100; intimob=100; double dawn=100.0; char alpha=‘d’; string st=“1”; • boy = Convert.ToByte(imob); • dawn = Convert.ToDouble(st); • imob= Convert.ToInt32(alpha); • alpha = Convert.ToChar(boy); • st = Convert.ToString(imob); boy = 100 i = 100 byte int int char dawn = 1 byte char alpha = ‘d’ double string st = 100

30. <type>.Parse(); • Convert string data to others • Example • d = double.Parse(st); byte b=100; int i=100; double d=100.0; char c=‘d’; string st=“1”; • i = int.Parse (st); • c = char.Parse(st); • b = byte.Parse(st); d = 1 i = 1 double string int string c = 1 b = 1

31. Test I • Write a program which • Input : Your name • Output : Your name is <your name>.

32. Test II • Write a program which • Input : 3 numbers • Output : average of the 3 input numbers

33. Test III • Write a program which • Input : Length of radius of circle • Output : Area of the circle