Code:

const int Sensor1 = 2 ;
int i;
void setup ()
{
  pinMode(Sensor1,INPUT);
}
void loop ()
{Sensor_1:
 // statement...............
}

void delay_function ()
{
for(i=0;i<10000;i++)
  {
  if (digitalRead(Sensor1) == 0)
     {
       goto Sensor_1 ;
     }
  }
}

can i use goto function to Transfers program flow between different functions such as goto from void delay_function()  to void loop()

i need to enable timer0 and when reach to 256 give flag

how i can set timer in arduino

i need make clock display second and minutes using arduino UNO R3

Yep.

With ordinary serial just connect RX from board A to TX on Board B, TX from Board A to RX on Board B and very important connect ground from board A to ground on board B.

Not need any code for interface

i need to send and receive data from UNO board to another one

Code:

lcd.setCursor(0,2);
lcd.print(line_percentage);
lcd.print("%");

when this code print in LCD give three number such as( 100%)  and when give two number (85%%) and when give  one number (0%%%)
i need to out (100%)  & (85%) & (0%)

board suddenly give me this message (avrdude  stk500_getsync    not in sync  resp 0x00) when upload any program

the board suddenly show this message (avrdude  stk500_getsync (): not in sync: resp=0x00)   when upload any program !!!

I mean the output shown in LCD appear small time  then disappear and repeat i need appear at all time

i need to show variable output without blinking in output and i need when the value of variable output change the LCD show this change

Code:

if(analogRead(sensor)==1023)
  {
   if(!flagged) 
    {  if (inputsignal == 1)                     // i need print "x" when analogRead(sensor)==1023 and when inputsignal == 1
        {
          Serial.print("x");
          Serial.println();
          flagged = 1;     
        }
    }   
  }
  else flagged =0;

please check this i need

You just need to keep track of past reading through the main loop:

Code:

const int sensor = A0; // analog input use variable resistance
int flagged = 0;  

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

void loop ()
{
  if(analogRead(sensor)==1023)//when variable resistance give value =1023 print 'x'
  {
   if(!flagged)
    {                             // i need to add if condition here and when it valid print "X"  , my problem: when i add if condition not print "x"
      Serial.print("x");
      Serial.println();
      flagged = 1;
    }
   else flagged =0;
  }
 
   delay (1000);
}

i need to add if condition as i shown in code

Your "x" never equals 1, because there is no input for it to change to 1 and at the top you have it as 2.

What are you trying to do with the code, what is its purpose?

The original code was to print out "x" only ONCE, if it equaled 1023 and if the input changed to a new number and then back to 1023.

ok i need add if condition before print "x" to the original code ( print " x " when if condition is valid ) 

do you add if condition    if (x==1)