Automatic AC Temperature Controller using Arduino, DHT11 and IR Blaster

Any idea of why I am getting this error?
I use code from someone and want to use it in my project. can someone tell me how to solve the error problem in the code.

/*
 * Automatic AC Temperature control using Arduino and TSOP
 * Code by: Aswinth Raj B
 * Dated: 25-10-2017
 * Website: www.circuitdigest.com
 * 
       S.No: Component Pin Arduino Pin
    1 OLED – Vcc  5V 
    2 OLED – Gnd  Gnd
    3 OLED- SCK, D0,SCL,CLK 4
    4 OLED- SDA, D1,MOSI, Data  3
    5 OLED- RES, RST,RESET  7
    6 OLED- DC, A0  5
    7 OLED- CS, Chip Select 6
    8 DHT11 – Vcc 5V
    9 DHT11 – Gnd Gnd
    10  DHT11 – Signal  13
    11  TSOP – Vcc  5V
    12  TSOP – Gnd  Gnd
    13  IR Led – Anode  9
    14  IR Led – Cathode  Gnd
 */
 
 #include <IRremote.h> //Lib for IT Blaster and TSOP
 #include <SPI.h> // Inbuilt Lib
 #include <Wire.h> //Inbuilt Lib
 #include <Adafruit_GFX.h> //Lib for OLED
 #include <Adafruit_SSD1306.h> //Lib for OLED
 #include <dht.h> //Library for dht11 Temperature and Humidity sensor (Download from Link in article)
 
 // Assign pins for OLED (Software config.)
#define OLED_MOSI  3
#define OLED_CLK   4
#define OLED_DC    5
#define OLED_CS    6
#define OLED_RESET 7
Adafruit_SSD1306 display(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

#define SSD1306_LCDHEIGHT 64 //Change if you are using a Different OLED

#define DHT11_PIN 13 //Sensor output pin is connected to pin 13
dht DHT; //Sensor object named as DHT

#define Desired_temperature 27 //The desired temperature is 27*C at any time

//Decoded Remote Signals For my AC ##CHANGE IT FOR YOUR REMOTE
unsigned int ACoff[] = {2950,1750, 400,1100, 450,1050, 450,400, 400,400, 400,400, 450,1100, 400,400, 400,400, 450,1100, 400,1100, 450,350, 450,1100, 400,400, 400,400, 450,1100, 400,1100, 450,400, 400,1100, 400,1100, 450,400, 400,400, 400,1100, 450,350, 450,400, 400,1100, 450,400, 400,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 450,350, 450,350, 450,1100, 400,400, 450,400, 400,1100, 450,1050, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,1100, 450,350, 450,400, 400,400, 400,400, 450,400, 400,1100, 450,350, 450,400, 400,400, 400,400, 400,1100, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 450,350, 450,350, 450,400, 400,1100, 450,350, 450,350, 450,400, 450,350, 450,350, 450,1100, 450};  
unsigned int ACon[] = {2950,1700, 450,1100, 400,1100, 450,350, 450,350, 450,400, 450,1050, 450,350, 450,400, 450,1050, 450,1100, 400,400, 450,1050, 450,350, 450,400, 400,1100, 450,1100, 450,350, 450,1050, 450,1100, 450,350, 450,350, 450,1100, 450,350, 400,400, 450,1100, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,1100, 400,400, 450,350, 450,1100, 400,400, 450,350, 450,1100, 400,1100, 450,350, 450,400, 400,400, 450,350, 500,300, 450,400, 450,350, 400,400, 450,1100, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,1100, 450,350, 400,400, 450,350, 450,400, 450,350, 400,400, 450,400, 450,350, 450,350, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 400,400, 450,350, 450,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 450,350, 400,400, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 450,350, 450,1100, 400,400, 400,400, 450,350, 450,350, 450,1100, 400,400, 450};
unsigned int Temp23[] = {3000,1650, 550,950, 550,1000, 500,300, 550,250, 550,250, 550,1000, 500,300, 550,300, 500,1000, 550,950, 550,300, 550,950, 550,250, 550,300, 500,1000, 500,1050, 500,300, 500,1000, 550,1000, 500,300, 500,300, 550,1000, 450,350, 500,300, 500,1050, 450,350, 450,350, 450,350, 450,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 450,1100, 400,400, 400,400, 450,1050, 450,400, 400,400, 450,1100, 400,1100, 400,400, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 450,350, 450,1100, 400,400, 400,400, 450,350, 450,400, 400,400, 450,1100, 400,400, 400,1100, 450,1100, 400,1100, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 450,350, 400,400, 450,350, 450,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,350, 450,1100, 400,1100, 450,1100, 400,1100, 450,1100, 400,1100, 400,400, 450};  
unsigned int Temp24[] = {3000,1650, 500,1050, 500,1000, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 500,300, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 500,300, 500,1000, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,1000, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,1000, 500,1050, 500,1000, 500,300, 500,350, 450,350, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,1050, 500,1000, 500,1050, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,300, 500,350, 500,300, 450,350, 500,350, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 500,350, 450,1050, 500,300, 500,1050, 500,1000, 500,1050, 500,1000, 500,1000, 500,350, 550};  
unsigned int Temp25[] = {3050,1650, 500,1000, 550,950, 550,300, 500,300, 500,300, 550,1000, 500,300, 500,300, 550,1000, 550,950, 550,250, 550,1000, 500,300, 550,250, 550,1000, 500,1000, 550,300, 550,950, 550,950, 550,300, 500,300, 500,1000, 550,250, 550,300, 550,950, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 600,250, 500,300, 550,250, 550,250, 550,300, 550,250, 500,300, 550,300, 500,300, 500,1000, 550,250, 550,300, 500,1000, 550,250, 550,300, 500,1000, 550,1000, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,1000, 550,950, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,950, 550,300, 500,1000, 550,1000, 500,1000, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 500,350, 500,1000, 500,1000, 500,1050, 500,1000, 500,1050, 500,300, 550};  
unsigned int Temp26[] = {3000,1650, 500,1000, 500,1050, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 450,350, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 500,300, 500,1000, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 450,350, 500,300, 500,1050, 500,1000, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,1050, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,300, 500,1050, 450,1050, 500,1000, 500,350, 500,300, 500,300, 500,350, 450,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 450,350, 500,300, 500,350, 450,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 450,1050, 500,1000, 500,350, 500,1000, 500,1000, 500,1050, 500,1000, 500,350, 500};  
unsigned int Temp27[] = {3050,1600, 550,1000, 500,1000, 550,300, 500,300, 550,250, 550,1000, 500,300, 550,300, 500,1000, 550,1000, 500,300, 550,1000, 550,250, 500,300, 550,1000, 500,1050, 500,300, 500,1000, 550,1000, 500,300, 550,250, 550,1000, 550,250, 550,300, 500,1000, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 500,1000, 550,300, 500,300, 550,1000, 500,300, 500,300, 550,1000, 550,1000, 500,300, 500,300, 550,250, 550,300, 500,300, 550,300, 500,300, 500,300, 550,1000, 500,300, 550,250, 550,300, 500,300, 500,300, 500,350, 500,300, 550,250, 550,1000, 500,1000, 550,1000, 500,300, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 500,300, 550,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 500,300, 500,350, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,1000, 500,1050, 500,1000, 500,350, 500};  // PANASONIC C4D3:64800024
unsigned int Temp28[] = {3100,1600, 550,950, 550,1000, 550,250, 550,250, 550,250, 550,1000, 500,300, 500,300, 550,1000, 500,1000, 550,250, 550,1000, 500,300, 550,250, 550,1000, 550,950, 550,300, 500,1000, 550,950, 550,300, 550,250, 500,1000, 550,300, 500,300, 550,950, 550,300, 500,300, 500,300, 550,250, 550,300, 550,250, 500,300, 550,300, 500,300, 500,300, 550,250, 550,250, 600,250, 500,300, 500,300, 550,300, 500,300, 500,1000, 550,300, 500,300, 500,1000, 550,250, 550,300, 500,1000, 550,1000, 550,250, 550,250, 550,250, 550,300, 500,300, 550,250, 550,1000, 500,1000, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,1000, 500,300, 500,1000, 550,1000, 500,1000, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 550,250, 500,300, 550,250, 550,250, 550,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,1000, 500,300, 500,300, 550,950, 550,1000, 500,1000, 550,1000, 500,300, 550};  
unsigned int Temp29[] = {3100,1550, 600,950, 500,1000, 550,300, 500,300, 500,300, 550,950, 550,300, 550,250, 550,1000, 500,1000, 550,250, 550,1000, 500,300, 550,250, 550,950, 600,950, 550,250, 550,1000, 500,1000, 550,250, 600,250, 550,950, 550,250, 550,300, 550,950, 550,250, 550,300, 550,250, 550,250, 550,250, 550,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,250, 600,250, 550,950, 550,250, 550,300, 500,1000, 550,250, 550,300, 550,950, 550,1000, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,1000, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,1000, 550,250, 550,1000, 500,1000, 550,1000, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 550,1000, 500,1000, 550,1000, 500,1000, 550,300, 500};  
unsigned int Temp30[] = {3000,1650, 500,1000, 550,1000, 500,300, 500,300, 550,250, 550,1000, 500,300, 500,300, 550,1000, 550,950, 550,250, 550,1000, 550,250, 550,250, 550,1000, 550,950, 550,300, 500,1000, 550,950, 550,300, 500,300, 550,950, 550,300, 550,250, 550,1000, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,950, 550,300, 500,300, 500,1000, 550,250, 550,300, 550,950, 550,1000, 500,300, 550,250, 550,250, 600,250, 500,300, 550,250, 550,1000, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,950, 550,300, 500,1000, 550,950, 550,1000, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,950, 500,1050, 500,1000, 500,350, 500,1000, 500,1000, 500,1050, 500,300, 500};  
//Change it for your remote

IRsend irsend;

int Measured_temp;
int Measured_Humi;
int AC_Temp;
char temp_error = 2;
int Pev_value;
boolean AC = false;

int khz = 38; // 38kHz carrier frequency for the NEC protocol

void setup()
{
Serial.begin(9600);
display.begin(SSD1306_SWITCHCAPVCC);
display.clearDisplay();
}

void loop() {
  
  DHT.read11(DHT11_PIN); //Read the Temp and Humidity
  Measured_temp = DHT.temperature + temp_error;
  Measured_Humi = DHT.humidity;

// text display tests
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.print("Temperature: "); display.print(Measured_temp);display.println("C");
  display.setCursor(0,10);
  display.print("Humidity: "); display.print(Measured_Humi);display.println("%");
  display.setCursor(0,20);
  display.print("AC Temp: "); display.print(AC_Temp);display.println("C");

  display.display();
  delay(500);
  display.clearDisplay();
 
 if ((Measured_temp <= (Desired_temperature-3)) && AC == true) //If AC is turned on and temperature is less than 3 degree of Desired value #24 turn off
 {
  irsend.sendRaw(ACoff, sizeof(ACoff) / sizeof(ACoff[0]), khz);  delay(2000);//Send signal to Turn Off the AC
  AC_Temp = 0; AC=false;
 }

 if ((Measured_temp >= Desired_temperature+4) && AC == false) //If AC is off and measured Temp is greater than Desired Temp
 {
  irsend.sendRaw(ACon, sizeof(ACon) / sizeof(ACon[0]), khz); delay(2000); //Send Signal to Turn On the AC 
  delay(2000);
  irsend.sendRaw(Temp27, sizeof(Temp27) / sizeof(Temp27[0]), khz); //Send signal to set 27*C
  AC_Temp = 27; AC=true;
 }

if ( Measured_temp != Pev_value) //Change the temperature only if the measured voltage value changes
{

if (Measured_temp == Desired_temperature+3) //If AC is ON and measured temp is very very high than desired
{
   irsend.sendRaw(Temp24, sizeof(Temp24) / sizeof(Temp24[0]), khz); delay(2000);//Send signal to set 24*C
  AC_Temp = 24; 
}

if (Measured_temp == Desired_temperature+2) //If AC is ON and measured temp is very high than desired
{
   irsend.sendRaw(Temp25, sizeof(Temp25) / sizeof(Temp25[0]), khz); delay(2000);//Send signal to set 25*C
  AC_Temp = 25; 
}

if (Measured_temp == Desired_temperature+1) //If AC is ON and measured temp is very high than desired
{
   irsend.sendRaw(Temp26, sizeof(Temp26) / sizeof(Temp26[0]), khz); delay(2000);//Send signal to set 26*C
  AC_Temp = 26; 
}

if (Measured_temp == 27 ) //If AC is ON and measured temp is desired value
{
  irsend.sendRaw(Temp27, sizeof(Temp27) / sizeof(Temp27[0]), khz); //Send signal to set 27*C
  AC_Temp = 27; 
}

if (Measured_temp == Desired_temperature-1) //If AC is ON and measured temp is low than desired value
{
  irsend.sendRaw(Temp28, sizeof(Temp28) / sizeof(Temp28[0]), khz); delay(2000);//Send signal to set 28*C
  AC_Temp = 28; 
}

if (Measured_temp == Desired_temperature-2 ) //If AC is ON and measured temp is very low than desired value
{
  irsend.sendRaw(Temp29, sizeof(Temp29) / sizeof(Temp29[0]), khz); delay(2000);//Send signal to set 29*C
  AC_Temp = 29; 
}

if (Measured_temp == Desired_temperature-3 ) //If AC is ON and measured temp is very very low desired value
{
  irsend.sendRaw(Temp30, sizeof(Temp30) / sizeof(Temp30[0]), khz); delay(2000);//Send signal to set 30*C
  AC_Temp = 30; 
}

}
Pev_value = Measured_temp;
}

error

In file included from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:29:0:
C:\Program Files (x86)\Arduino\libraries\DHT-sensor/DHT.h:37:0: warning: "DEBUG_PRINT" redefined
 #define DEBUG_PRINT(...)                                                       \
 
In file included from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.hpp:215:0,
                 from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.h:10,
                 from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:24:
C:\Program Files (x86)\Arduino\libraries\IRremote/IRremoteInt.h:160:0: note: this is the location of the previous definition
 #  define DEBUG_PRINT(...) void()
 
In file included from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:29:0:
C:\Program Files (x86)\Arduino\libraries\DHT-sensor/DHT.h:39:0: warning: "DEBUG_PRINTLN" redefined
 #define DEBUG_PRINTLN(...)                                                     \
 
In file included from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.hpp:215:0,
                 from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.h:10,
                 from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:24:
C:\Program Files (x86)\Arduino\libraries\IRremote/IRremoteInt.h:164:0: note: this is the location of the previous definition
 #  define DEBUG_PRINTLN(...) void()
 
C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:39:0: warning: "SSD1306_LCDHEIGHT" redefined
 #define SSD1306_LCDHEIGHT 64 //Change if you are using a Different OLED
 
In file included from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:28:0:
C:\Program Files (x86)\Arduino\libraries\Adafruit_SSD1306/Adafruit_SSD1306.h:115:0: note: this is the location of the previous definition
 #define SSD1306_LCDHEIGHT 32 ///< DEPRECATED: height w/SSD1306_128_32 defined
 
Coding_Project:42:1: error: 'dht' does not name a type
 dht DHT; //Sensor object named as DHT
 ^~~
C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino: In function 'void loop()':
Coding_Project:79:6: error: expected unqualified-id before '.' token
   DHT.read11(DHT11_PIN); //Read the Temp and Humidity
      ^
Coding_Project:80:22: error: expected primary-expression before '.' token
   Measured_temp = DHT.temperature + temp_error;
                      ^
Coding_Project:81:22: error: expected primary-expression before '.' token
   Measured_Humi = DHT.humidity;
                      ^
exit status 1
'dht' does not name a type

My libraries DHT.h

/*!
 *  @file DHT.h
 *
 *  This is a library for DHT series of low cost temperature/humidity sensors.
 *
 *  You must have Adafruit Unified Sensor Library library installed to use this
 * class.
 *
 *  Adafruit invests time and resources providing this open source code,
 *  please support Adafruit andopen-source hardware by purchasing products
 *  from Adafruit!
 *
 *  Written by Adafruit Industries.
 *
 *  MIT license, all text above must be included in any redistribution
 */

#ifndef DHT_H
#define DHT_H

#include "Arduino.h"

/* Uncomment to enable printing out nice debug messages. */
//#define DHT_DEBUG

#define DEBUG_PRINTER                                                          \
  Serial /**< Define where debug output will be printed.                       \
          */

/* Setup debug printing macros. */
#ifdef DHT_DEBUG
#define DEBUG_PRINT(...)                                                       \
  { DEBUG_PRINTER.print(__VA_ARGS__); }
#define DEBUG_PRINTLN(...)                                                     \
  { DEBUG_PRINTER.println(__VA_ARGS__); }
#else
#define DEBUG_PRINT(...)                                                       \
  {} /**< Debug Print Placeholder if Debug is disabled */
#define DEBUG_PRINTLN(...)                                                     \
  {} /**< Debug Print Line Placeholder if Debug is disabled */
#endif

/* Define types of sensors. */
static const uint8_t DHT11{11};  /**< DHT TYPE 11 */
static const uint8_t DHT12{12};  /**< DHY TYPE 12 */
static const uint8_t DHT21{21};  /**< DHT TYPE 21 */
static const uint8_t DHT22{22};  /**< DHT TYPE 22 */
static const uint8_t AM2301{21}; /**< AM2301 */

#if defined(TARGET_NAME) && (TARGET_NAME == ARDUINO_NANO33BLE)
#ifndef microsecondsToClockCycles
/*!
 * As of 7 Sep 2020 the Arduino Nano 33 BLE boards do not have
 * microsecondsToClockCycles defined.
 */
#define microsecondsToClockCycles(a) ((a) * (SystemCoreClock / 1000000L))
#endif
#endif

/*!
 *  @brief  Class that stores state and functions for DHT
 */
class DHT {
public:
  DHT(uint8_t pin, uint8_t type, uint8_t count = 6);
  void begin(uint8_t usec = 55);
  float readTemperature(bool S = false, bool force = false);
  float convertCtoF(float);
  float convertFtoC(float);
  float computeHeatIndex(bool isFahrenheit = true);
  float computeHeatIndex(float temperature, float percentHumidity,
                         bool isFahrenheit = true);
  float readHumidity(bool force = false);
  bool read(bool force = false);

private:
  uint8_t data[5];
  uint8_t _pin, _type;
#ifdef __AVR
  // Use direct GPIO access on an 8-bit AVR so keep track of the port and
  // bitmask for the digital pin connected to the DHT.  Other platforms will use
  // digitalRead.
  uint8_t _bit, _port;
#endif
  uint32_t _lastreadtime, _maxcycles;
  bool _lastresult;
  uint8_t pullTime; // Time (in usec) to pull up data line before reading

  uint32_t expectPulse(bool level);
};

/*!
 *  @brief  Class that defines Interrupt Lock Avaiability
 */
class InterruptLock {
public:
  InterruptLock() {
#if !defined(ARDUINO_ARCH_NRF52)
    noInterrupts();
#endif
  }
  ~InterruptLock() {
#if !defined(ARDUINO_ARCH_NRF52)
    interrupts();
#endif
  }
};

#endif

Please Help me how to fix this.

Look like you might be using the wrong library, or have the wrong library installed.

#include <dht.h> //Library for dht11 Temperature and Humidity sensor (Download from Link in article)

This is not DHT.h

I have fixed DHT.h but still get an error

Can you post your new code.

You need to ensure it lines up with the methods that are available within the library you are using.

From what you posted previously it looked like the code was indeed written for a dht.h library, but that was not available, and needed to be.

/*
 * Automatic AC Temperature control using Arduino and TSOP
 * Code by: Aswinth Raj B
 * Dated: 25-10-2017
 * Website: www.circuitdigest.com
 * 
       S.No: Component Pin Arduino Pin
    1 OLED – Vcc  5V 
    2 OLED – Gnd  Gnd
    3 OLED- SCK, D0,SCL,CLK 4
    4 OLED- SDA, D1,MOSI, Data  3
    5 OLED- RES, RST,RESET  7
    6 OLED- DC, A0  5
    7 OLED- CS, Chip Select 6
    8 DHT11 – Vcc 5V
    9 DHT11 – Gnd Gnd
    10  DHT11 – Signal  13
    11  TSOP – Vcc  5V
    12  TSOP – Gnd  Gnd
    13  IR Led – Anode  9
    14  IR Led – Cathode  Gnd
 */
 
 #include <IRremote.h> //Lib for IT Blaster and TSOP
 #include <SPI.h> // Inbuilt Lib
 #include <Wire.h> //Inbuilt Lib
 #include <Adafruit_GFX.h> //Lib for OLED
 #include <Adafruit_SSD1306.h> //Lib for OLED
 #include <DHT.h> //Library for dht11 Temperature and Humidity sensor (Download from Link in article)
 
 // Assign pins for OLED (Software config.)
#define OLED_MOSI  3
#define OLED_CLK   4
#define OLED_DC    5
#define OLED_CS    6
#define OLED_RESET 7
Adafruit_SSD1306 display(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

#define SSD1306_LCDHEIGHT 64 //Change if you are using a Different OLED

#define DHT11_PIN 13 //Sensor output pin is connected to pin 13
dht DHT; //Sensor object named as DHT

#define Desired_temperature 27 //The desired temperature is 27*C at any time

//Decoded Remote Signals For my AC ##CHANGE IT FOR YOUR REMOTE
unsigned int ACoff[] = {2950,1750, 400,1100, 450,1050, 450,400, 400,400, 400,400, 450,1100, 400,400, 400,400, 450,1100, 400,1100, 450,350, 450,1100, 400,400, 400,400, 450,1100, 400,1100, 450,400, 400,1100, 400,1100, 450,400, 400,400, 400,1100, 450,350, 450,400, 400,1100, 450,400, 400,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 450,350, 450,350, 450,1100, 400,400, 450,400, 400,1100, 450,1050, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,1100, 450,350, 450,400, 400,400, 400,400, 450,400, 400,1100, 450,350, 450,400, 400,400, 400,400, 400,1100, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 450,350, 450,350, 450,400, 400,1100, 450,350, 450,350, 450,400, 450,350, 450,350, 450,1100, 450};  
unsigned int ACon[] = {2950,1700, 450,1100, 400,1100, 450,350, 450,350, 450,400, 450,1050, 450,350, 450,400, 450,1050, 450,1100, 400,400, 450,1050, 450,350, 450,400, 400,1100, 450,1100, 450,350, 450,1050, 450,1100, 450,350, 450,350, 450,1100, 450,350, 400,400, 450,1100, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,1100, 400,400, 450,350, 450,1100, 400,400, 450,350, 450,1100, 400,1100, 450,350, 450,400, 400,400, 450,350, 500,300, 450,400, 450,350, 400,400, 450,1100, 400,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,1100, 450,350, 400,400, 450,350, 450,400, 450,350, 400,400, 450,400, 450,350, 450,350, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 400,400, 450,350, 450,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 450,350, 400,400, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 450,350, 450,1100, 400,400, 400,400, 450,350, 450,350, 450,1100, 400,400, 450};
unsigned int Temp23[] = {3000,1650, 550,950, 550,1000, 500,300, 550,250, 550,250, 550,1000, 500,300, 550,300, 500,1000, 550,950, 550,300, 550,950, 550,250, 550,300, 500,1000, 500,1050, 500,300, 500,1000, 550,1000, 500,300, 500,300, 550,1000, 450,350, 500,300, 500,1050, 450,350, 450,350, 450,350, 450,400, 450,350, 450,350, 450,400, 400,400, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 450,1100, 400,400, 400,400, 450,1050, 450,400, 400,400, 450,1100, 400,1100, 400,400, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 450,350, 450,1100, 400,400, 400,400, 450,350, 450,400, 400,400, 450,1100, 400,400, 400,1100, 450,1100, 400,1100, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,350, 450,400, 450,350, 400,400, 450,350, 450,400, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,350, 450,1100, 400,1100, 450,1100, 400,1100, 450,1100, 400,1100, 400,400, 450};  
unsigned int Temp24[] = {3000,1650, 500,1050, 500,1000, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 500,300, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 500,300, 500,1000, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,1000, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,1000, 500,1050, 500,1000, 500,300, 500,350, 450,350, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,1050, 500,1000, 500,1050, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,300, 500,350, 500,300, 450,350, 500,350, 450,350, 450,350, 450,350, 450,400, 400,400, 400,400, 450,400, 400,400, 400,400, 400,400, 450,350, 450,400, 400,400, 450,350, 450,400, 450,350, 450,350, 450,350, 450,400, 450,350, 450,350, 450,350, 500,350, 450,1050, 500,300, 500,1050, 500,1000, 500,1050, 500,1000, 500,1000, 500,350, 550};  
unsigned int Temp25[] = {3050,1650, 500,1000, 550,950, 550,300, 500,300, 500,300, 550,1000, 500,300, 500,300, 550,1000, 550,950, 550,250, 550,1000, 500,300, 550,250, 550,1000, 500,1000, 550,300, 550,950, 550,950, 550,300, 500,300, 500,1000, 550,250, 550,300, 550,950, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 600,250, 500,300, 550,250, 550,250, 550,300, 550,250, 500,300, 550,300, 500,300, 500,1000, 550,250, 550,300, 500,1000, 550,250, 550,300, 500,1000, 550,1000, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,1000, 550,950, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,950, 550,300, 500,1000, 550,1000, 500,1000, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 500,350, 500,1000, 500,1000, 500,1050, 500,1000, 500,1050, 500,300, 550};  
unsigned int Temp26[] = {3000,1650, 500,1000, 500,1050, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 450,350, 500,1000, 500,300, 500,350, 500,1000, 500,1050, 500,300, 500,1000, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,300, 500,300, 500,1050, 450,350, 500,300, 500,1050, 500,1000, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,1000, 500,300, 500,1050, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,300, 500,1050, 450,1050, 500,1000, 500,350, 500,300, 500,300, 500,350, 450,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 450,350, 500,300, 500,350, 450,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 500,300, 500,300, 500,300, 500,350, 500,300, 500,300, 500,350, 450,1050, 500,1000, 500,350, 500,1000, 500,1000, 500,1050, 500,1000, 500,350, 500};  
unsigned int Temp27[] = {3050,1600, 550,1000, 500,1000, 550,300, 500,300, 550,250, 550,1000, 500,300, 550,300, 500,1000, 550,1000, 500,300, 550,1000, 550,250, 500,300, 550,1000, 500,1050, 500,300, 500,1000, 550,1000, 500,300, 550,250, 550,1000, 550,250, 550,300, 500,1000, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 500,1000, 550,300, 500,300, 550,1000, 500,300, 500,300, 550,1000, 550,1000, 500,300, 500,300, 550,250, 550,300, 500,300, 550,300, 500,300, 500,300, 550,1000, 500,300, 550,250, 550,300, 500,300, 500,300, 500,350, 500,300, 550,250, 550,1000, 500,1000, 550,1000, 500,300, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 500,300, 550,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 500,300, 500,350, 500,300, 500,350, 500,300, 500,300, 500,1050, 500,1000, 500,1050, 500,1000, 500,350, 500};  // PANASONIC C4D3:64800024
unsigned int Temp28[] = {3100,1600, 550,950, 550,1000, 550,250, 550,250, 550,250, 550,1000, 500,300, 500,300, 550,1000, 500,1000, 550,250, 550,1000, 500,300, 550,250, 550,1000, 550,950, 550,300, 500,1000, 550,950, 550,300, 550,250, 500,1000, 550,300, 500,300, 550,950, 550,300, 500,300, 500,300, 550,250, 550,300, 550,250, 500,300, 550,300, 500,300, 500,300, 550,250, 550,250, 600,250, 500,300, 500,300, 550,300, 500,300, 500,1000, 550,300, 500,300, 500,1000, 550,250, 550,300, 500,1000, 550,1000, 550,250, 550,250, 550,250, 550,300, 500,300, 550,250, 550,1000, 500,1000, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,1000, 500,300, 500,1000, 550,1000, 500,1000, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 550,250, 500,300, 550,250, 550,250, 550,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,1000, 500,300, 500,300, 550,950, 550,1000, 500,1000, 550,1000, 500,300, 550};  
unsigned int Temp29[] = {3100,1550, 600,950, 500,1000, 550,300, 500,300, 500,300, 550,950, 550,300, 550,250, 550,1000, 500,1000, 550,250, 550,1000, 500,300, 550,250, 550,950, 600,950, 550,250, 550,1000, 500,1000, 550,250, 600,250, 550,950, 550,250, 550,300, 550,950, 550,250, 550,300, 550,250, 550,250, 550,250, 550,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,250, 600,250, 550,950, 550,250, 550,300, 500,1000, 550,250, 550,300, 550,950, 550,1000, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,1000, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 550,300, 500,1000, 550,250, 550,1000, 500,1000, 550,1000, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,250, 550,1000, 500,1000, 550,1000, 500,1000, 550,300, 500};  
unsigned int Temp30[] = {3000,1650, 500,1000, 550,1000, 500,300, 500,300, 550,250, 550,1000, 500,300, 500,300, 550,1000, 550,950, 550,250, 550,1000, 550,250, 550,250, 550,1000, 550,950, 550,300, 500,1000, 550,950, 550,300, 500,300, 550,950, 550,300, 550,250, 550,1000, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,300, 500,300, 500,300, 550,950, 550,300, 500,300, 500,1000, 550,250, 550,300, 550,950, 550,1000, 500,300, 550,250, 550,250, 600,250, 500,300, 550,250, 550,1000, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,950, 550,300, 500,1000, 550,950, 550,1000, 500,300, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,250, 550,300, 500,300, 550,250, 550,300, 500,300, 500,300, 550,250, 550,300, 500,300, 550,950, 500,1050, 500,1000, 500,350, 500,1000, 500,1000, 500,1050, 500,300, 500};  
//Change it for your remote

IRsend irsend;

int Measured_temp;
int Measured_Humi;
int AC_Temp;
char temp_error = 2;
int Pev_value;
boolean AC = false;

int khz = 38; // 38kHz carrier frequency for the NEC protocol

void setup()
{
Serial.begin(9600);
display.begin(SSD1306_SWITCHCAPVCC);
display.clearDisplay();
}

void loop() {
  
  DHT.read11(DHT11_PIN); //Read the Temp and Humidity
  Measured_temp = DHT.temperature + temp_error;
  Measured_Humi = DHT.humidity;

// text display tests
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.print("Temperature: "); display.print(Measured_temp);display.println("C");
  display.setCursor(0,10);
  display.print("Humidity: "); display.print(Measured_Humi);display.println("%");
  display.setCursor(0,20);
  display.print("AC Temp: "); display.print(AC_Temp);display.println("C");

  display.display();
  delay(500);
  display.clearDisplay();
 
 if ((Measured_temp <= (Desired_temperature-3)) && AC == true) //If AC is turned on and temperature is less than 3 degree of Desired value #24 turn off
 {
  irsend.sendRaw(ACoff, sizeof(ACoff) / sizeof(ACoff[0]), khz);  delay(2000);//Send signal to Turn Off the AC
  AC_Temp = 0; AC=false;
 }

 if ((Measured_temp >= Desired_temperature+4) && AC == false) //If AC is off and measured Temp is greater than Desired Temp
 {
  irsend.sendRaw(ACon, sizeof(ACon) / sizeof(ACon[0]), khz); delay(2000); //Send Signal to Turn On the AC 
  delay(2000);
  irsend.sendRaw(Temp27, sizeof(Temp27) / sizeof(Temp27[0]), khz); //Send signal to set 27*C
  AC_Temp = 27; AC=true;
 }

if ( Measured_temp != Pev_value) //Change the temperature only if the measured voltage value changes
{

if (Measured_temp == Desired_temperature+3) //If AC is ON and measured temp is very very high than desired
{
   irsend.sendRaw(Temp24, sizeof(Temp24) / sizeof(Temp24[0]), khz); delay(2000);//Send signal to set 24*C
  AC_Temp = 24; 
}

if (Measured_temp == Desired_temperature+2) //If AC is ON and measured temp is very high than desired
{
   irsend.sendRaw(Temp25, sizeof(Temp25) / sizeof(Temp25[0]), khz); delay(2000);//Send signal to set 25*C
  AC_Temp = 25; 
}

if (Measured_temp == Desired_temperature+1) //If AC is ON and measured temp is very high than desired
{
   irsend.sendRaw(Temp26, sizeof(Temp26) / sizeof(Temp26[0]), khz); delay(2000);//Send signal to set 26*C
  AC_Temp = 26; 
}

if (Measured_temp == 27 ) //If AC is ON and measured temp is desired value
{
  irsend.sendRaw(Temp27, sizeof(Temp27) / sizeof(Temp27[0]), khz); //Send signal to set 27*C
  AC_Temp = 27; 
}

if (Measured_temp == Desired_temperature-1) //If AC is ON and measured temp is low than desired value
{
  irsend.sendRaw(Temp28, sizeof(Temp28) / sizeof(Temp28[0]), khz); delay(2000);//Send signal to set 28*C
  AC_Temp = 28; 
}

if (Measured_temp == Desired_temperature-2 ) //If AC is ON and measured temp is very low than desired value
{
  irsend.sendRaw(Temp29, sizeof(Temp29) / sizeof(Temp29[0]), khz); delay(2000);//Send signal to set 29*C
  AC_Temp = 29; 
}

if (Measured_temp == Desired_temperature-3 ) //If AC is ON and measured temp is very very low desired value
{
  irsend.sendRaw(Temp30, sizeof(Temp30) / sizeof(Temp30[0]), khz); delay(2000);//Send signal to set 30*C
  AC_Temp = 30; 
}

}
Pev_value = Measured_temp;
}

still an error

In file included from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:29:0:
C:\Program Files (x86)\Arduino\libraries\DHT-sensor/DHT.h:37:0: warning: "DEBUG_PRINT" redefined
 #define DEBUG_PRINT(...)                                                       \
 
In file included from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.hpp:215:0,
                 from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.h:10,
                 from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:24:
C:\Program Files (x86)\Arduino\libraries\IRremote/IRremoteInt.h:160:0: note: this is the location of the previous definition
 #  define DEBUG_PRINT(...) void()
 
In file included from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:29:0:
C:\Program Files (x86)\Arduino\libraries\DHT-sensor/DHT.h:39:0: warning: "DEBUG_PRINTLN" redefined
 #define DEBUG_PRINTLN(...)                                                     \
 
In file included from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.hpp:215:0,
                 from C:\Program Files (x86)\Arduino\libraries\IRremote/IRremote.h:10,
                 from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:24:
C:\Program Files (x86)\Arduino\libraries\IRremote/IRremoteInt.h:164:0: note: this is the location of the previous definition
 #  define DEBUG_PRINTLN(...) void()
 
C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:39:0: warning: "SSD1306_LCDHEIGHT" redefined
 #define SSD1306_LCDHEIGHT 64 //Change if you are using a Different OLED
 
In file included from C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino:28:0:
C:\Program Files (x86)\Arduino\libraries\Adafruit_SSD1306/Adafruit_SSD1306.h:115:0: note: this is the location of the previous definition
 #define SSD1306_LCDHEIGHT 32 ///< DEPRECATED: height w/SSD1306_128_32 defined
 
Coding_Project:42:1: error: 'dht' does not name a type
 dht DHT; //Sensor object named as DHT
 ^~~
C:\Users\Arep\Documents\Anas polipd\Sem 5\Project 2\Coding_Project\Coding_Project.ino: In function 'void loop()':
Coding_Project:79:6: error: expected unqualified-id before '.' token
   DHT.read11(DHT11_PIN); //Read the Temp and Humidity
      ^
Coding_Project:80:22: error: expected primary-expression before '.' token
   Measured_temp = DHT.temperature + temp_error;
                      ^
Coding_Project:81:22: error: expected primary-expression before '.' token
   Measured_Humi = DHT.humidity;
                      ^
exit status 1
'dht' does not name a type

thanks for the response

Your code is written for a different library.

You have 2 options.. try and find the library it was written for... this comment seem to indicate it was linked from the web page you were on...

//Library for dht11 Temperature and Humidity sensor (Download from Link in article)

Use a different library.. the one you now have included DHT.h

But.. you will need to change your code to match. Try the link above for details.

You may just have the case the wrong way round, check the examples for your library.

I would have expected to see:

DHT dht;