Control 4 digital outputs with one switch

As usual with programming, there are many solutions, for example:

1. You can use a bitmask, put 4 variables in an array with binary values 1000, 0100, 0010 and 0001 and when the switch is pressed, you store the value into each LED pin by comparing the value.
2. However, a more simpler solution is just use a counter from 0 to 4, if the value is 1, the first LED should be one, then after a switch increase the value, and use modulo 5 (% 5) to go back to 0.

To check if a button is clicked, use a boolean, which check against the previous value. Also implement the debounce algorithm which can be found at the Arduino site.

Without debouncing it could look like this:

#include "stdlib.h"

int buttonPin    =   7;
int buttonState  = LOW;

int led1Pin      =   8;
int led2Pin      =   9;
int led3Pin      =  10;
int led4Pin      =  11;
int ledMode      =   0; // All off, 1-4 means LED 1-4 is on


void setup()
{
}


void loop()
{
   // Add debouncing yourself
   if ((buttonState == LOW) && (digitalRead(buttonPin) == HIGH))
   {
      buttonState = HIGH;
      ledMode = (ledMode + 1) % 5;
   }
   else if ((buttonState == HIGH) && (digitalRead(buttonPin) == LOW))
   {
      buttonState = LOW;
   }

   digitalWrite(led1Pin, ledMode == 1 ? HIGH : LOW);
   digitalWrite(led2Pin, ledMode == 2 ? HIGH : LOW);
   digitalWrite(led3Pin, ledMode == 3 ? HIGH : LOW);
   digitalWrite(led4Pin, ledMode == 4 ? HIGH : LOW);
}

If you put the LEDs on subsequent pins, you can use the following code which is more simpler and works for any number of LEDs:

#include "stdlib.h"

int buttonPin    =   7;
int buttonState  = LOW;

int nrOfLeds     =   4;
int startLed     =   8;
int ledMode      =   0; // All off, 1 means led on pin startLed, 2 means led on pin startLed + 1 etc.


void setup()
{
}


void loop()
{
   // Add debouncing yourself
   if ((buttonState == LOW) && (digitalRead(buttonPin) == HIGH))
   {
      buttonState = HIGH;
      ledMode = (ledMode + 1) % (nrOfLeds + 1);
   }
   else if ((buttonState == HIGH) && (digitalRead(buttonPin) == LOW))
   {
      buttonState = LOW;
   }

   for (int led = 0; led < nrOfLeds; ledPin++)
   {
       digitalWrite(startLed + led, ledMode == led + 1 ? HIGH : LOW);
   }
}