Creating a JavaDB with Netbeans

I am starting to put my hands on Java. Its quite amazing to see how Java connects to databases. Almost the same for all cases(tried Oracle,JavaDB). Just puting the code here to get in future.

Lets first start with creating and connecting to a JavaDB using netbeans.

first go to the services tab.

Expand the Database entry.

right click the JavaDB and click start server.

Right click again the JavaDB to create a new Database. The database create wizard shall appear.

Just type in the fields as indicated to continue this tutorial. the password is also "app".

connect to the newly created database. (right click and connect).

Expand the APP. and right click "Tables" to create a table. The table creator wizard appears.

Create your table using this wizard. When done Expand the Tables section to view your newly created table. You can add data to it if you want.

C Programming Basic - Part 1

C is a widely used language to program, specially useful for learning basic concepts of porgramming. C uses various compilers. Each of these compilers is slightly different. Each one should support the ANSI standard C functions, but each compiler will also have nonstandard functions (these functions are similar to slang spoken in different parts of a country). Sometimes the use of nonstandard functions will cause problems when you attempt to compile source code (the actual C code written by a programmer and saved as a text file) with a different compiler. These tutorials use ANSI standard C and should not suffer from this problem; fortunately, since C has been around for quite a while, there shouldn't be too many compatability issues except when your compiler tries to create C++ code.

Every full C program begins inside a function called "main". A function is simply a collection of commands that do "something". The main function is always called when the program first executes. From main, we can call other functions, whether they be written by us or by others or use built-in language features. To access the standard functions that comes with your compiler, you need to include a header with the #include directive. What this does is effectively take everything in the header and paste it into your program. Let's look at a working program:

#include 
 

int main()
{
  printf( "Hello world!" );
  return 0;

}

Let's look at the elements of the program. The #include is a "preprocessor" directive that tells the compiler to put code from the header called stdio.h into our program before actually creating the executable. By including header files, you can gain access to many different functions ( the printf ) function is included in stdio.h.

The next imporant line is int main(). This line tells the compiler that there is a function named main, and that the function returns an integer, hence int. The "curly braces" ({ and }) indicate the beginning and end of the function.

The printf function is the standard C way of displaying output on the screen. The quotes tell the compiler that you want to output the literal string as-is (almost).

Finally, at the end of the program, we return a value from main to the operating system by using the return statement. This return value is important as it can be used to tell the operating system whether our program succeeded or not. A return value of 0 means success.

The final brace closes off the function.

Interesting isn't it ? Start playing around with this. To know about compiler, you may refer to here

Compiler

What is a compiler?
A compiler is necessary to make your source code (..c, .cpp, or .cc files) into a running program. If you're just starting out, you'll need to make sure that you have one before you start. There are many compilers available



Terminology:

Compile convert a source code file into an executable, but strictly speaking, compilation is an intermediate step

Link The act of taking compiled code and turning it into an executable

Build A build refers to the process of creating the end executable (what is often colloquially refered to as compilation).

Compiler Generally, compiler refers to both a compiler and a "linker"

Linker The program that generates the executable by linking

IDE Integrated Development Environment, a combination of a text editor and a compiler, such that you can compile and run your programs directly within the IDE. IDEs facilitates debugging.

Compilers:

Windows/DOS

• Code::Blocks and MINGW Our recommended free compiler setup!
• Borland Find out how to download and set up Borland's free command-line compiler
• DJGPP Read about DJGPP, a DOS-based compiler
• Dev-C++ and Digital Mars Read about Dev-C++, a good windows based compiler, and Digital Mars

Windows Only

• Microsoft Visual C++ you must have heard about Visual C++

*nix

• g++ is a C++ compiler that comes with most *nix distributions.
• gcc is a C(and many other) compiler that comes with most *nix distributions.

Macintosh

• Apple's own Macintosh Programmer's Workshop is a compiler I've never used, but it is direct from apple and free.
• Codewarrior My experiences with Codewarrior are limited to Java programming, though it's gotten good reviews in the past. It's a full IDE rather than just a compiler, meaning that it has a text editor and debugger integrated with the compiler so you can do all your work from one place. 

To know about how to compile you can refer to their manual.  GCC compilation process is given here

Assembly Language Part 3

For 8086 programs to perform useful tasks, there must be a way to make decisions and repeat sections of the code. Inthis section we will discuss the the basic flow control instructions of MASM

In assembly program flow is managed by jumping isntructions. There are 2 types of jump

1) Unconditional
             The JMP instruction causes an unconditional transfer of control. The basic form is-
            JMP label

2)Conditional
            The transfer of control depends on the previous instruction. It is often done by CMP. for example
          CMP operand1,operand2
          Jxx    end

Here the jump Jxx can be any of the following -

Jcc Instructions for Signed Comparisons

Instruction	Description	Condition	Aliases	Opposite
JG	Jump if greater (>)	Sign = Ovrflw or Zero=0	JNLE	JNG
JNLE	Jump if not less than or equal (not <=)	Sign = Ovrflw or Zero=0	JG	JLE
JGE	Jump if greater than or equal (>=)	Sign = Ovrflw	JNL	JGE
JNL	Jump if not less than (not <)	Sign = Ovrflw	JGE	JL
JL	Jump if less than (<)	Sign Ovrflw	JNGE	JNL
JNGE	Jump if not greater or equal (not >=)	Sign Ovrflw	JL	JGE
JLE	Jump if less than or equal (<=)	Sign Ovrflw or Zero = 1	JNG	JNLE
JNG	Jump if not greater than (not >)	Sign Ovrflw or Zero = 1	JLE	JG
JE	Jump if equal (=)	Zero = 1	JZ	JNE
JNE	Jump if not equal ()	Zero = 0	JNZ	JE

Jcc Instructions That Test Flags

Instruction	Description	Condition	Aliases	Opposite
JC	Jump if carry	Carry = 1	JB, JNAE	JNC
JNC	Jump if no carry	Carry = 0	JNB, JAE	JC
JZ	Jump if zero	Zero = 1	JE	JNZ
JNZ	Jump if not zero	Zero = 0	JNE	JZ
JS	Jump if sign	Sign = 1	-	JNS
JNS	Jump if no sign	Sign = 0	-	JS
JO	Jump if overflow	Ovrflw=1	-	JNO
JNO	Jump if no Ovrflw	Ovrflw=0	-	JO
JP	Jump if parity	Parity = 1	JPE	JNP
JPE	Jump if parity even	Parity = 1	JP	JPO
JNP	Jump if no parity	Parity = 0	JPO	JP
JPO	Jump if parity odd	Parity = 0	JNP	JPE

Jcc Instructions for Unsigned Comparisons

Instruction	Description	Condition	Aliases	Opposite
JA	Jump if above (>)	Carry=0, Zero=0	JNBE	JNA
JNBE	Jump if not below or equal (not <=)	Carry=0, Zero=0	JA	JBE
JAE	Jump if above or equal (>=)	Carry = 0	JNC, JNB	JNAE
JNB	Jump if not below (not <)	Carry = 0	JNC, JAE	JB
JB	Jump if below (<)	Carry = 1	JC, JNAE	JNB
JNAE	Jump if not above or equal (not >=)	Carry = 1	JC, JB	JAE
JBE	Jump if below or equal (<=)	Carry = 1 or Zero = 1	JNA	JNBE
JNA	Jump if not above (not >)	Carry = 1 or Zero = 1	JBE	JA
JE	Jump if equal (=)	Zero = 1	JZ	JNE
JNE	Jump if not equal ()	Zero = 0	JNZ	JE

 As we have seen earlier that the conditional jump isntruction is often followed by the CMP instruction. Wnen CPU executes the CMP instruction it compares the first operand with the second operand. Then if the condition described by the following jump instruction is true - a change of flow control is occured. You may want to see the example -

       CMP AX,BX
       JL  axislower    ;  If AX is lower than BX then control transferred to axislower

The TEST instruction
    The TEST instruction performs an AND operation, but does not store
the result. It only sets the FLAGS register based on what the result would
be (much like how the CMP instruction performs a subtraction but only sets
FLAGS).

TEST DESTINATION, SOURCE


Effect on flags -

SF,ZF, PF - Reflect the result

AF  -  Undefined

CF,OF - 0                    

The test instruction can be used to examine individual bits in a operand. For that case the mask(source) should contain 1s in the desired bit positions and 0s in the rest. See the pseudocode and MASM code -

IF AL is EVEN
   THEN JUMP TO END_X

MASM code-

TEST AL,1
JZ END_X

END_X:
  

If we wish to check the 1st bit we TEST it by 1. (here the mask is 1 i.e = 0000 0001 in binary. And we know that an even number shall have 1 in the 1st bit position.)
The and product should be zero if 1st bit is 0, the AL would then remain same but the ZF (zero flag = 0 if result is zero) is 0. So the JZ instruction shall be executed.

 Further reading:
 The art of Assembly Language             URL:  http://www.arl.wustl.edu/

 The Intel Microprocessor Architecture, Programming & Interfacing
    by  Barry B. Brey

Assembly Language Part 4

Conditional Branching in MASM
We have shown that the jump instructions can be used to implement branches and looops. However these instructions are difficult for beginners to apply as a substitute of high level branching statements.

In high level languages we use these basic structures -

IF-THEN
The if-then structure is the most common type of branching statement used. The pseudocode for IF-THEN is :


IF  CONDITION IS TRUE
     THEN EXECUTE TRUE BRANCH STATEMENTS
END_IF

MASM example:
Suppose we want to code the following pseudocode in MASM

IF AX< 0
    THEN REPLACE AX WITH ITS COMPLIMENTED VALUE
END_IF

The MASM code will be:

CMP AX,0
   JNL END_IF
   NEG AX

END_IF:

IF-THEN-ELSE
The if-then-else structure is the expansion of most common type of branching statement IF-THEN. The pseudocode for IF-THEN-ELSE is :

IF   Condition is TRUE
THEN
Execute true-branch statements
ELSE
Execute false-branch statements
END_IF

Lets explain by applying the following pseudocode in MASM

IF AL<= BL
  THEN
      DISPLAY THE CHARACTER IN AL
  ELSE
      DISPLAY THE CHARACTER IN BL
 END_IF

The MASM code will be -

MOV AH,2
CMP AL,BL
   JNBE ELSE_
   MOV DL,AL
   JMP DISPLAY_
ELSE_:
   MOV DL,BL
DISPLAY_:
   INT 21H

END_IF:


CASE
The case in high-level language is a multiway branch structure that tests a register, variable or expression for particular values or range of values. The pseudocode is :

CASE expression
    value_1: statement_1
    value_2: statement_2
    value_3: statement_3
    value_4: statement_4
    .................................
    value_n: statement_n
END_CASE

Consider the following pseudocode in MASM

IF AX a negative number
   THEN put -1 in BX
IF AX contains 0
   THEN put 0 in BX
IF AX contains a positive number
   THEN put 1 in BX

The MASM code will be -

CMP AX,0
   JL   NEGATIVE_
   JG   POSITIVE
 
   MOV BX,0
   JMP END_CASE

 NEGATIVE_:
   MOV BX,-1
   JMP END_CASE

POSITIVE_:
  MOV BX,1
  JMP END_CASE

END_CASE:


further reading:
http://www.cs.princeton.edu/

Assembly Language Programming and Organization of IBM PC
                                                                    Ytha Yu
                                                                    Charles Marut

Assembly Language Part 5

Looping instructions in Assembly

What comes to your mind after watching the loop at the left? That's it the Head is Touching the Tail at some point.

In assembly a loop is a sequence of instructions that is repeated like the loop to the left.
The final instruction (Tail) jumps (touches) to the first instruction (Head).

The basic form of looping in Assembly is

REPEAT UNTIL
REPEAT
      STATEMENTS
UNTIL CONDITION

For example if we want to read all input characters given by the user until he/she inputs

    MOV AH,1
REPEAT_:
    INT 21H
    CMP AL,' '
    JNE REPEAT_ 

Some other frequently used looping structures are-


FOR LOOP
In these kind of lop structures the instructions are repeated for known number of times. pseudocode -

FOR loop_count times DO
     statements
END_FOR

In assembly we use the instruction LOOP to implement for loop. The general form is-

LOOP header_label

Here header label is the name or label of the instruction block to be executed in the loop. The LOOP instruction uses CX as the counter so it has to be defined first. When the program executes LOOP it first checks if CX = 0 if true it continues to execute the next instructions. If the CX !=0 then control is transferred to the "header_label" , at the same time it also decreases the value of CX by 1. 

Let us implement it in the program to print 100 '*' in assembly.

MOV CX,80
MOV AH,2
MOV DL,'*'

TOP:                            ; header_label
   INT 21H
   LOOP TOP              



WHILE LOOP
These kind of loops depends on a condition. pseudocode -


WHILE   condition DO
   statements
END_WHILE

The condition is checked at the top of the loop. If the condition is satisfied the the statements are executed. If false  the program skips to whatever follows. It is possible that the condition is never satisfied (even at the initial stage) in that case the body is never executed.

Lets count the number of character in the input line.

MOV DX,0
MOV AH,1
INT 21H

WHILE_:
     CMP AL,13
     JE END_WHILE
     INC  DX
     INT 21H
     JMP WHILE_

END_WHILE:


The basic difference between WHILE and REPEAT loop is that using WHILE loop gives opportunity to skip the whole process even at the initial stage if the condition is false.
On the other hand the statements of REPEAT has to be done atleast once. REPEAT is useful on other cases as it leads to shorter coding.

Further reading:
Assembly Language Programming and Organization of IBM PC
                                                                    Ytha Yu
                                                                    Charles Marut
http://www.cs.princeton.edu/

Assembly Language Part 6

Logic Instructions

The ability to manipulate the individual bits of a Data is one of the key advantages of assembly language. In order to do so we use Logic instructions. Let us first remind the basic ligic instructions for now,

AND 

 0 0 -> 0

 1 0 -> 0

 0 1 -> 0

 1 1 -> 1

OR 

 0 0 -> 0

 1 0 -> 1

 0 1 -> 1

           1 1 -> 1            

XOR 

 0 0 -> 0

 1 0 -> 1

 0 1 -> 1

 1 1 -> 0

NOT

 0 -> 1

 1 -> 0

 

Now lets see where we use these functions in Assembly -

AND   ->  To clear
OR     ->  To set
XOR   ->  To compliment desired bit positions
NOT   ->  To compliment all bits

AND (Used to Clear )

The form is

AND DESTINATION, SOURCE

Suppose we want to clear the sign bit of AL then the code will be

AND AL,7Fh                            ;

we know that the sign bit is the MSB so if we AND it with the value which has all 1s except of the MSB as 0 then

AL   =   10101100

Msk =   01111111

-----------------------------

rslt  =   00101100

OR (used to set)

The form is

OR DESTINATION, SOURCE

Suppose we want to set the sign bit of AL then the code will be

OR AL,80h                            ;

we know that the sign bit is the MSB so if we OR it with the value which has all 0s except of the MSB as 1 then

AL   =   00101100

Msk =   10000000

-----------------------------

rslt  =   10101100

XOR (Used to compliment selected bits )

The form is

XOR DESTINATION, SOURCE

Suppose we want to change the sign bit of AL then the code will be

XOR AL,80h                            ;

we know that the sign bit is the MSB so if we XOR it with the value which has all 0s except of the MSB which is 1 then

AL   =   10101100

Msk =   10000000

-----------------------------

rslt  =   00101100

Here you may have noticed that destination bit is complimented if that bit position of the Mask is 1 and unchanged if it is 0. (XOR x , 0 - x) (XOR  x,1)= x'

NOT (Used to compliment all bits )

The form is

NOT DESTINATION

Suppose we want to invert all the bits of AL then the code will be

NOT AL                            ;

You can see that NOT takes only one argument.

Suppose AL = 10110010 , after executing the NOT instruction it will be 01001101

Problem (Convert ASCII value to number)

When we enter a character in Assembly the equivalent ASCII value is stored in the memory. Say we pressed 3 then the ASCII value 33h will be saved in AL. we have to convert it to 3...

If we AND a value with 0000  1111 then the relust will be 30 less than the original value

AL   =   0011 0011   =33
Msk =   0000 1111
------------------------------
             0000 1111   =3

so the code will be

AND AL, 0Fh