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;

}

1. Have two indexes pointing to two ends of array, say i and j.

2. Approach towards each other with a check condition that they dont cross each other.

3. Each iteration of while loop, swap the numbers pointed by two indexes when num[i] index number is not equal to 1.

void sort()

{

     int a[]={1,0,0,0,1,1,0,1,0,1,0,0,1,0};

     int i=0;

     int j=13;

     int temp;

      while(j>i)

     {

          if(a[i]==1)

                 i++;

          if(a[j]==0)

                 j--;

          if(a[i]==0)

         {

                 temp=a[i];

                a[i]=a[j];

                a[j]=temp;

         }

     } 

     for(i=0;i<14;i++)

             Console.Write(a[i]+", ");

}

Output: 1,1,1,1,1,1,0,0,0,0,0,0,0

The main types of system calls are as follows:

Process Control: These types of system calls are used to control the processes. Some examples are end, abort, load, execute, create process, terminate process etc.

File Management: These types of system calls are used to manage files. Some examples are Create file, delete file, open, close, read, write etc.

Device Management: These types of system calls are used to manage devices. Some examples are Request device, release device, read, write, get device attributes etc.

Information Maintenance: These types of system calls are used to set system data and get process information. Some examples are time, OS parameters, id, time used etc.

Communications: These types of system calls are used to establish a connection. Some examples are send message, received messages, terminate etc

UDP (User Datagram Protocol) is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP).

A 32 bit processor is faster than a 64 bit processor, 64 bit processors are very commonly used that you can find it easily in any home pc but the main difference is the hardware you are having on your machine. For 32 bits there isn't any need of any wide main bus to carry 32 bits at a time but for 64 bits its must that you should have a wider bus to carry 64bits.

Dual boot system allows you to install and maintain two operating systems on a single PC. The purpose for this is to maintain compatibility between older and newer software. For example, there maybe programs that only work under Windows 98, therefore having a dual boot system between Windows 98 and another version like Windows XP is a good choice.