1. Input & Output Statement
Computer & Programming
Group
Dept. of Computer Engineering
Kasetsart University
Adopted from Thanomkulabut’s experiences.
Brushed up by MikeLab.Net
Version 2012

2. Review
Data Type
Arithmetic Operators
Math Class

3. Data Types Type Size Description Range bool 1 byte Store truth value
true / false
char
Store one character
character code 0 – 255
byte
Store positive integer
0 – 255
short
2 byte
Store integer
-32, ,767
int
4 byte
-2.1 x x 109
long
8 byte
-9.2 x x 1018
double
16 byte
Store real number
± 5.0x ± 1.7x10308
string
N/A
Store sequence of characters

4. Priority of Arithmetic Operators
high
Operators
Associativity
Type ()
left to right
parentheses
unary postfix
++x --x + - (type)
unary prefix
* / %
multiplicative
+ -
additive
= += -= *= /= %=
x++, x--
right to left
assignment
low

5. Arithmetic Operators Example
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
Given x = 3.0, y = 2.0, b =2, what is the output?
x/y*++b
x/y*b++ 3 2
Answer: 4.5
Answer: 3.0

6. 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)
Statement
Description
var += expression
Increment var by the value of expression
var -= expression
Decrement var by the value of expression
var *= expression
Multiply var by the value of expression, then store the result in var
var /= expression
Divide var by the value of expression, then store the result in var
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. The Math Class Math Class Method/ Constant Value returned Example Call
Result PI
Value of 
Math.PI
Max(x,y)
Larger of the two
Math.Max(1,2) 2
Abs(x)
Absolute value of x
Math.Abs(-1.3)
1.3
Sqrt(x)
Square-root of x
Math.Sqrt(4.0)
2.0
Round(x)
Nearest integer to x
Math.Round(0.8) 1
Pow(x,y) xy
Math.Pow(3,2)
9.0
Log(x)
Natural log of x
Math.Log(10)
Floor(x)
Greatest integer smaller than or equal to x
Math.Floor(4.9) 4
Ceiling(x)
Smallest integer greater than or equal to x
Math.Ceiling(4.1) 5
Cos(x)
Cosine of x radians
Math.Cos(Math.PI) -1

9. Today’s Outline Input Statements Output Statements Data Conversions
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(); Console.Read();
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 ….
string st = Console.ReadLine();
Run-time error may be occurred if user’s input is incorrect

13. Console.ReadLine() Example
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.
int i;
Console.Write(“Input char:”);
i = Console.Read();
Console.WriteLine(i);
Input char: A 65

15. Output Statements

16. Output Statements Console.Write(); Console.WriteLine(); Show output
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 string integer Console.Write(“Happy”);
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}
= 9
{1}
{0}
{2}

20. Advanced Usage (2) 20

21. Advanced Usage (3) int a = 10; Symbol Meaning Example Output
D , d
Decimal
Console.WriteLine(“ {0:D} ",a}; 10
E , e
Exponential
Console.WriteLine(“ {0:E} ",a};
E+001
F , f
Fix Point
Console.WriteLine(“ {0:F} ",a};
10.00
P , p
Percent
Console.WriteLine(“ {0:P} ",a};
1, %
For a complete list of format specifiers, see

22. Escape Sequences Characters
What should you do if you would like to write “C:\mydocument”
Console.WriteLine(““C:\mydocument””);
Symbols
Output \’
Single Quote \”
Double Quote \\
Backslash \n
New line \t
Horizontal tab
\uxxxx
Unicode escape sequence for character with hex value xxxx.
Console.WriteLine(“\“C:\mydocument\””);
Console.WriteLine(“\“C:\\mydocument\””); 

23. Unicode Characters เกม 0e01 0e21 0e40
Console.Write(“\u0e40\u0e01\u0e21”);
เกม
Reference:

24. Data Conversions

25. Losing some information!!!
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 Arithmetic promotion
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/anIntVar is converted 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, int i, long l
i = (int)b; l = (long)b + (long)i;
int
byte
int
long
long

28. Casting (2) 100% 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; int imob=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
char
alpha = ‘d’
byte
double
string
st = 100

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