DeCLarations GENerator : used to create the host language copy books for the table    definitions. Also creates the DECLARE table.

Cursor is a programming device that allows the SELECT to find a set of rows but return them one at a time. Cursor should be used because the host language  can deal with only one row at a time.

Both these are used to combine the results of different SELECT statements.

    UNION       - Selects only distinct values 

    UNION ALL - Selects duplicate values also

Syntax:

    SELECT column_name(s) FROM table1

    UNION / UNION ALL

    SELECT column_name(s) FROM table2;

Notice that each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order.

Use SELECT DISTINCT ..... in DB2 query

The DISTINCT keyword can be used to return only distinct (different) values.

Syntax:

     SELECT DISTINCT column1,column2

      FROM table_name;

Marshalling is the process of gathering data from one or more applications or non-contiguous sources in computer storage, putting the data pieces into a message buffer, and organizing or converting the data into a format that is prescribed for a particular receiver or programming interface.  

A system call is a function.subroutine which interrupts the currently executing program and transfers control to the interrupt routine.The contents of the executing program are saved and after the interrupt routine finishes its function,control is transferred back to the executing program. If we talk in the context of Linux then System calls are called kernel mode.

Whereas API (Application Programming Interface) is a function or a set of functions, objects, protocols or data-structures for the support of application development for developers/programmers. It is actually a kind of function definition which specifies how to make available of a specific service of the system/OS to the other program/process or system. Read more at: https://www.queryhome.com/48442/os-what-is-difference-between-system-call-and-api

public class Test {

    public void replaseSpaces(char[] str, int length) {

        int spaceCount = 0, newLength = 0, i = 0;

        for(i = 0; i < length; i++) {

            if (str[i] == ' ') 

                spaceCount++;

        }

        newLength = length + (spaceCount * 2);

        str[newLength] = '\0';

        for(i = length - 1; i >= 0; i--) {

            if (str[i] == ' ') {

                str[newLength - 1] = '0';

                str[newLength - 2] = '2';

                str[newLength - 3] = '%';

                newLength = newLength - 3;

            }

            else {

                str[newLength - 1] = str[i];

                newLength = newLength - 1;

            }

        }

        System.out.println(str);

    }

    public static void main(String[] args) {

        Test tst = new Test();

        char[] ch = {'t', 'h', 'e', ' ', 'd', 'o', 'g', ' ', ' ', ' ', ' ', ' ', ' '};

        int length = 6;

        tst.replaseSpaces(ch, length);  

    }

}

This problem isn't too hard. You just need to start at the head of the list, and iterate to the end. At each node, swap the values of pNext and pPrev. Finally, set pHead to the last node in the list.

Node * pCurrent = pHead, *pTemp;

while (pCurrent)

{

  pTemp = pCurrent->pNext;

  pCurrent->pNext = pCurrent->pPrev;

  pCurrent->pPrev = temp;  

  pHead = pCurrent;

  pCurrent = temp;

}