Solution :
#include<LiquidCrystal.h>
int value;
int flag;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup()
{
lcd.begin(16, 2);
Serial.begin(9600);
}
void loop()
{
value=digitalRead(7);
if(value==0){
flag=1;}
if(value==1){
flag=~flag;}
if (flag==1){
lcd.setCursor(0,0);
lcd.print("number is");
lcd.setCursor(2,1);
lcd.print(random(0, 255));
delay(1000);
}
else{
lcd.setCursor(0,0);
lcd.print("Not Pressed");
delay(1000);
lcd.clear();}
}