how to interpret the serial data

is it functional if the computer will send two type of data for example {fff},is it posible to use two start and end maker...

is it posible to use two start and end maker...

Yes, but...

is easier to deal with. Save all the data, then use strtok() to parse into jvvmv and fff.

With two start and end markers, you need two arrays, and you need to keep track of which array to store a character in. Does f go in the first buffer or the second buffer?

what i need to do?

you need to start thinking for longer than 20 minutes at a time, and working through some of the examples in the IDE. I believe I've said this before, but it's worth repeating.

(Hint: you haven't written anything called "sendCommand" yet.)

i got it...thank you very much

This example may help you grasp the basics.

Code for Arduino:

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println(analogRead(A0));
  delay(2);
}

Code for Processing:

 import processing.serial.*;

 Serial myPort;        // The serial port
 int xPos = 1;         // horizontal position of the graph

 void setup () {
 // set the window size:
 size(400, 300);        

 // List all the available serial ports
 println(Serial.list());
 // I know that the first port in the serial list on my mac
 // is always my  Arduino, so I open Serial.list()[0].
 // Open whatever port is the one you're using.
 myPort = new Serial(this, Serial.list()[0], 9600);
 // don't generate a serialEvent() unless you get a newline character:
 myPort.bufferUntil('\n');
 // set inital background:
 background(0);
 }
 void draw () {
 // everything happens in the serialEvent()
 }

 void serialEvent (Serial myPort) {
 // get the ASCII string:
 String inString = myPort.readStringUntil('\n');

 if (inString != null) {
 // trim off any whitespace:
 inString = trim(inString);
 // convert to an int and map to the screen height:
 float inByte = float(inString); 
 inByte = map(inByte, 0, 1023, 0, height);

 // draw the line:
 stroke(127,34,255);
 line(xPos, height, xPos, height - inByte);

 // at the edge of the screen, go back to the beginning:
 if (xPos >= width) {
 xPos = 0;
 background(0); 
 } 
 else {
 // increment the horizontal position:
 xPos++;
 }
 }
 }