Last Updated: 20/07/2021

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Lesson 4 - for loop

Lessons >> Basics >> Lesson 4 - for loop

Lesson Contents

Using "for loop" to control program flow
Using different Comparison Operators,< (smaller than) and > (greater than)
INcreasing and decreasing values in the foor loop
Negative values in the loop
Nested "for loops"
Nesting "for loops" with "if else"
Adding a second integer variable
Understanding how delay() works inside and outside the "for loop"

Example 1: forLoopv1.ino

Click to Download code:forLoopv1.ino

Simple introduction to the "for loop"

 
/* 21/07/2021
   forLoopv1

   Purpose, learn "for loop control"


*/

//An int is an integer, a Number, any value between -32,768 and 32,767
int q;



void setup() {
  // Serial.begin(9600) starts serial communication. 9600bps bits per second = 1200 characters per second
  Serial.begin(9600);
  //Send script name
  Serial.println("forLoopv1...");
  //this will print a blank line
  Serial.println(" ");

}

void loop() {
  
  
  //q starts with a value of Zero, the loop continues while q smaller than 20
  for(q=0;q<20;q++){
    //print the value of q to the serial monitor
    Serial.print("Val q: ");
    Serial.println(q);
    //delay within the for loop
    delay(100);  
  }
  //delay outside the for loop
  delay(1000);

  
}

Example 2: forLoopv2.ino

Click to Download code:forLoopv2.ino

Increasing and decreasing the value of "q" in the "for loop"
"for loop" with negative values.

 
/* 21/07/2021
   forLoopv2

   Purpose, to see different versions of the for loop code


*/

//An int is an integer, a Number, any value between -32,768 and 32,767
int q;



void setup() {
  // Serial.begin(9600) starts serial communication. 9600bps bits per second = 1200 characters per second
  Serial.begin(9600);
  //Send script name
  Serial.println("forLoopv2...");
  //this will print a blank line
  Serial.println(" ");

}

void loop() {
  
  //Example 1
  Serial.print("Example 1");
  //q starts with a value of Zero, the loop continues while q smaller than 20
  for(q=0;q<20;q++){
    //print the value of q to the serial monitor
    Serial.print("Val q: ");
    Serial.println(q);
    //delay within the for loop
    delay(100);  
  }
  //delay outside the for loop
  delay(1000);
  
  //example 2
  Serial.print("Example 2");
  
  for(q=30;q<40;q++){
    //print the value of q to the serial monitor
    Serial.print("Val q: ");
    Serial.println(q);
    //delay within the for loop
    delay(100);  
  }
  //delay outside the for loop
  delay(1000);

  //example 3
  Serial.print("Example 3");
  //q is reducing in value through the loop
  //q-- subtracts 1 from the value of q
  for(q=50;q>35;q--){
    //print the value of q to the serial monitor
    Serial.print("Val q: ");
    Serial.println(q);
    //delay within the for loop
    delay(100);  
  }
  //delay outside the for loop
  delay(1000);

  //example 4
  Serial.print("Example 4");
  //q is reducing in value through the loop
  //q-- subtracts 1 from the value of q
  //displays q going negative
  for(q=10;q>-10;q--){
    //print the value of q to the serial monitor
    Serial.print("Val q: ");
    Serial.println(q);
    //delay within the for loop
    delay(100);  
  }
  //delay outside the for loop
  delay(1000);
}

Example 3: forLoopv3.ino

Click to Download code:forLoopv3.ino

Nested "for loops"
introducing a second variable

 
/* 21/07/2021
   forLoopv3

   Purpose, nest for loops


*/

//An int is an integer, a Number, any value between -32,768 and 32,767
int q;
int w;



void setup() {
  // Serial.begin(9600) starts serial communication. 9600bps bits per second = 1200 characters per second
  Serial.begin(9600);
  //Send script name
  Serial.println("forLoopv3...");
  //this will print a blank line
  Serial.println(" ");

}

void loop() {
  
  //Nested for loops
  Serial.println("Nested Loop");
  //q starts with a value of Zero, the loop continues while q smaller than 20
  for(q=0;q<20;q++){
    for(w=10;w>-1;w--){
      //print the value of q to the serial monitor
      Serial.print("Val q: ");
      Serial.print(q);
      Serial.print(" Val w: ");
      Serial.println(w);
      //delay within the for loop
      delay(100); 
    }
      
  }
  //delay outside the for loop
  delay(1000);
  
}

Example 4: forLoopv4.ino

Click to Download code:forLoopv4.ino

Nesting "for loops" and "if else"

 
/* 21/07/2021
   forLoopv4

   Purpose, nest "for loops" and "if else"


*/

//An int is an integer, a Number, any value between -32,768 and 32,767
int q;
int w;



void setup() {
  // Serial.begin(9600) starts serial communication. 9600bps bits per second = 1200 characters per second
  Serial.begin(9600);
  //Send script name
  Serial.println("forLoopv4...");
  //this will print a blank line
  Serial.println(" ");

}

void loop() {

  //Nested for loops and if
  Serial.println("Nested for and if");
  //q starts with a value of Zero, the loop continues while q smaller than 20
  for (q = 0; q < 20; q++) {
    if (q == 5) {
      for (w = 10; w > -1; w--) {
        //print the value of q to the serial monitor
        Serial.print("q: ");
        Serial.print(q);
        Serial.print(" w: ");
        Serial.println(w);
        //delay within the for loop
        delay(100);
      }
    } else {
      Serial.print("q: ");
      Serial.println(q);
    }


  }
  //delay outside the for loop
  delay(1000);

}

Additional Resource Links

Don't forget to use the Reference in you Arduino IDE and look at the Control Structures for loop and Comparison Operators for more help on this lesson.

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