const int LED = 13; // the pin for the LED
const int BUTTON = 7; // the input pin where the  pushbutton is connected
int val = 0; // val will be used to store the state of the input pin
int old_val = 0; // this variable stores the previous value of "val"
int state = 0; // 0 = LED off and 1 = LED on

void setup() 
{
pinMode(LED, OUTPUT); // tell Arduino LED is an output
pinMode(BUTTON, INPUT); // and BUTTON is an input
}

void loop()
{
val = digitalRead(BUTTON); // read input value and store it
// check if there was a transition
if ((val == HIGH) && (old_val == LOW))
{
state = 1 - state;
}

old_val = val; // val is now old, let's store it
if (state == 1) 
{
digitalWrite(LED, HIGH); // turn LED ON
} 
else 
{
digitalWrite(LED, LOW);
}
}

 const int LED = 13; // the pin for the LED
const int BUTTON = 7; // the input pin where the pushbutton is connected
int val = 0; // val will be used to store the state of the input pin
int old_val = 0; // this variable stores the previous value of "val"
int state = 0; // 0 = LED off and 1 = LED on

void setup() 
{
pinMode(LED, OUTPUT); // tell Arduino LED is an output
pinMode(BUTTON, INPUT); // and BUTTON is an input
}

void loop()
{
val = digitalRead(BUTTON); // read input value and store it
// check if there was a transition
if ((val == HIGH) && (old_val == LOW))
{
state = 1 - state; // same as state=!state;
delay(10);
}

old_val = val; // val is now old, let's store it

if (state == 1) 
{
digitalWrite(LED, HIGH); // turn LED ON
} 
else 
{
digitalWrite(LED, LOW);
}

}

pinMode(2,INPUT);
pinMode (3,OUTPUT);

pinMode(2,INPUT_PULLUP);

void setup() 
{
pinMode(2,INPUT_PULLUP);
pinMode (3,OUTPUT);
}
void loop() {
  // put your main code here, to run repeatedly:
  if (digitalRead(2) == LOW)
  {
    digitalWrite(3,HIGH);
  }
  else
  {
    digitalWrite(3,LOW);  
  }
}

digitalRead(pin)

 int ledPin = 13; // LED connected to digital pin 13
int inPin = 7; // pushbutton connected to digital pin 7
int val = 0; // variable to store the read value

void setup()
{
pinMode(ledPin, OUTPUT); // sets the digital pin 13 as output
pinMode(inPin, INPUT); // sets the digital pin 7 as input
}

void loop()
{
val = digitalRead(inPin); // read the input pin
digitalWrite(ledPin, val); // sets the LED to the button's value
}

 if (someVariable > 50)
{
// do something here
}

if (x > 120) digitalWrite(LEDpin, HIGH);

if (x > 120)
digitalWrite(LEDpin, HIGH);

if (x > 120) {digitalWrite(LEDpin, HIGH);} // all are correct

x == y (x is equal to y)
x != y (x is not equal to y)
x < y (x is less than y)
x > y (x is greater than y)
x <= y (x is less than or equal to y)
x >= y (x is greater than or equal to y)

if (pinFiveInput < 500)
{
// action A
}
else
{
// action B
}

if (pinFiveInput < 500)
{
// do Thing A
}
else if (pinFiveInput >= 1000)
{
// do Thing B
}
else
{
// do Thing C
}

int LEDpin = 5; // LED on pin 5
int switchPin = 13; // momentary switch on 13, other side connected to ground
boolean running = false;

void setup()
{
pinMode(LEDpin, OUTPUT);
pinMode(switchPin, INPUT);
digitalWrite(switchPin, HIGH); // turn on pullup resistor
}

void loop()
{
if (digitalRead(switchPin) == LOW)
{ // switch is pressed – pullup keeps pin high normally
delay(100); // delay to debounce switch
running = !running; // toggle running variable
digitalWrite(LEDpin, running) // indicate via LED
}
}

if (digitalRead(2) == 1 && digitalRead(3) == 1) { // read two switches
// ...
}

 if (a >= 10 && a <= 20){} // true if a is between 10 and 20

 if (x > 0 || y > 0) {
// ...
}

if (!x) {
// ...
}

/* Basic Arduino example code for displaying text on 16x2, 20x4 etc. character LCDs. */
// Include the library:
#include <LiquidCrystal.h>

// Create an LCD object. Parameters: (RS, E, D4, D5, D6, D7):
LiquidCrystal lcd = LiquidCrystal(2, 3, 4, 5, 6, 7);

void setup() {
  // Specify the LCD's number of columns and rows. Change to (20, 4) for a 20x4 LCD:
  lcd.begin(16, 2);
}

void loop() {
  // Set the cursor on the third column and the first row, counting starts at 0:
  lcd.setCursor(2, 0);

  // Print the string 'Hello World!':
  lcd.print("Hello World!");

  // Set the cursor on the third column and the second row:
  lcd.setCursor(2, 1);

  // Print the string 'LCD tutorial':
  lcd.print("LCD tutorial");
}

// Include the library:
#include <LiquidCrystal.h>

// Create an LCD object. Parameters: (RS, E, D4, D5, D6, D7):
LiquidCrystal lcd = LiquidCrystal(2, 3, 4, 5, 6, 7);

void setup() {
  // Specify the LCD's number of columns and rows. Change to (20, 4) for a 20x4 LCD:
  lcd.begin(16, 2);
}

void loop() {
  // Set the cursor on the third column and the first row, counting starts at 0:
  lcd.setCursor(2, 0);

  // Print the string 'Hello World!':
  lcd.print("Hello World!");

  // Set the cursor on the third column and the second row:
  lcd.setCursor(2, 1);

  // Print the string 'LCD tutorial':
  lcd.print("LCD tutorial");
}