DHT11

To use DHT11 we will use Adafruit's DHT and Unified sensor libraries.
To add these libraries goto Sketch > Include Libraries > Manage Libraries Hatchnhack_Arduino_Ide_Libraries Search and install DHT sensor library and Adafruit Unified Sensor library. Hatchnhack_Arduino_Ide_Libraries_DHT11 Hatchnhack_Arduino_Ide_Libraries_Adafruit Further if you want to manually install the libraries, they can be downloaded using the following links

DHT Sensor Library: Adafruit DHT Sensor Adafruit Unified Sensor Lib: Adafruit Unified Sensor

Example :

Measuring temperature and humidity using DHT11 on ARBD 1

#include "DHT.h"        //Include the DHT sensor library

#define DHT_TYPE DHT11  //Define DHT sensor type
#define DHT_PIN A0      //Define Pin connected to DHT sensor
DHT dht(DHT_PIN, DHT_TYPE);

void setup() {
    Serial.begin(115200);
    Serial.print(DHT_TYPE);
    Serial.println(" Sensor Test");
    dht.begin();
}
void loop(){
    float h = dht.readHumidity();
    float t = dht.readTemperature();
    if(isnan(h) || isnan(t)){
        Serial.println("Error!! Reading from DHT sensor");
        return;
    }
    Serial.println("===========================");
    Serial.print(" Humidity : ");
    Serial.print(h);
    Serial.println("%");
    Serial.print(" Temperature : ");
    Serial.print(t);
    Serial.print("\xC2\xB0");
    Serial.println("C");  
    Serial.println("===========================");
    delay(1000);
}