Digital output

    const int outPin=3;
    void setup(){ 
    
    pinMode(outPin, OUTPUT);
    
    Serial.begin(9600);
    
    
    Serial.println("Enter 1 or 0");
    
    
    }
      
    void loop(){
    if (Serial.available()>0){
    
  
    char ch=Serial.read();
     
    if (ch=='1'){
    digitalWrite(outPin, HIGH);}
    else if (ch=='0'){ 
    
    digitalWrite  (outPin, LOW);}
    }
    }
    

Digital input

     const int inputPin=5;
     void setup(){ 
     pinMode(inputPin, INPUT); 
     Serial.begin(9600);
     }
     
     void loop(){
     int reading = digitalRead (inputPin);
     Serial.println(reading);
     delay (1000);
     }
     

Analog output

     const int outputPin=3
     
     void  setup(){
     pinMode (outputPin, OUTPUT);
     Serial.begin (9600);
     Serial.println ("Enter Vots: 0-5");
     }
    
     void loop(){
     if (Serial.available>0){
     float volts = Serial.parseFloat();
     int pwmValue=volts*255.0/5.0;
     analogWrite (out putPin, pwmValue;
     }
     }
     
     

Analog input

     const int analogPin= A0;
     
     void setup(){
     Serial.begin (9600);
     }
     
     void loop(){
     int reading=analogRead (analogPin);
     float voltage = reading/204.6;
     Serial.print ("Reading=");
     Serial.print (reading);
     Serial.print (\t\t Volt=");
     Serial.println (voltage);
     delay (500);
     }