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Note : If you are an absolute beginner to programming, it is a good idea to use the code+blocks programming option in Tinkercad, and copy over the generated C++ code to Arduino IDE.

Comments

• Comments are for you – the programmer or any other human who might read your code

• Comments are not run on the Arduino board

C++	Blocks
Code Block language cpp

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/* multi-line comment */ Code Block language cpp

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// single line comment

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Statements

• Statements are compiled into an ‘executable’ of 1s and 0s, which are run on the Arduino.

• Statements end with a ;

C++	Blocks
Code Block language cpp

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c = a+b; // c is assigned the sum of a, b

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Variables

• Variables are containers to store intermediate data

• In C language, a variable needs to have a type, which specifies the nature and the size of data it holds

• Some of the standard data types are

• int : 16-bit integers in the range -32,768 to 32,767

• unsigned

  int 

  int : 16-bit positive integers (incl 0), 0 to 65535

• char : 8-bit integers from -128 to 127. Characters such as ‘0’, ‘A’, ‘a’, etc. are represented using ASCII (48, 65, 97 respectively - read up more!). BYTE is the same as unsigned char

• float : for floating point numbers such as 2.25, -5.875 (32-bits)

• Types can also be user-defined (

  through 

  through classes)

• Variables can be declared with or without initialization

C++	Blocks
Code Block language cpp

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int a; // declaration int a = 0; // declaration and initialization

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Image Added Note: Creating a variable in Blocks declares it and initializes it to 0

A variable appearing on the left-hand side of an assignment statement assigns a value to it.

C++	Blocks
Code Block language cpp

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a = 10; // assigning 10 to a

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A variable value is used when it appears in a comparison or on the right-hand side of an expression/assignment.

C++	Blocks
Code Block language cpp

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(a == 1) // checking if a is equal to 1

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The comparison above returns a 'true' or 'false', which is usually used for selection or iteration. Read up more about comparison operators! Important : In C++, '==' is a comparison operator, '=' is the assignment operator. Using one instead of the other will not cause a syntax error, but will cause incorrect program functionality.

C++	Blocks
Code Block language cpp

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b = a + 10; // variable b is assigned the value of variable a plus 10.

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Selection

• A program that executes all the statements in a sequence is probably not very interesting.

• Sometimes, a part of a program must be executed based on a certain condition (selection).

• Given below is an example of

  an 

  an if-else

   statement

   statement. The {} is optional if there is only one line being executed conditionally for if or else.

C++	Blocks
Code Block language cpp

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if(a>0){ c = a+b; //executed when a>0 } else{ c = a-b; //executed when a<0 or a==0 }

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To Do : Read up about about switch-case

Iteration

• Sometimes, a part of a program must be executed repeatedly until a certain condition is satisfied (iteration / loop)

• Given below is an example for

  an 

  an while loop.

C++	Blocks
Code Block language cpp

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while(a>0){ a = a-b; /* executed over and over until a<0 or a==0 */ }

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To Do : Read up about about for loop, do-while loop loop

Functions

• A function is a segment of code which can be invoked from different parts of the program in a parameterized manner

• A function involves 3 aspects

• Declaration (typically done in header files with extension .h)

int

...

 add(int,

...

int)

...

• Definition (typically done by the library vendor)

...

int add(int x, int y){ // x, y are function 'parameters'

...

                        //of the function 'add’

...

  return x+y;

...

}

• Usage (usually, we need to do only this)

...

{
  … //other statements

...

...

 
    c = add(a,b);

...

...

/* causes add() to be called with a, b passed as arguments.

...

...

    The value returned is assigned to c */
 
  … //other statements

...

}

Note : Blocks do not allow you to declare or define functions explicitly. However, some built-in functions such as digitalWrite() can be called using appropriate blocks, as shown below.

  digitalWrite

C++	Blocks
Code Block

{

language cpp {   digitalWrite(11, HIGH);

}

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Setup() and loop() functions

• Setup and loop are functions called automatically (unlike all other functions needs to be called explicitly)

• setup() is

  called 

  called once, when you release the reset button / plug in your Arduino / upload a new code onto the board

• loop() is

  called 

  called repeatedly; anything inside the loop() gets executed over and over as long as the system remains powered on

...

Note : When using blocks, any setup code required is automatically inserted into setup(). The main program logic which implemented using blocks goes into loop().

...

Good code is code which is readable, comprehensible, and extensible. If you can't read/comprehend, you can't debug the code, you can't improve the code, you can't collaborate in a team. Hence the importance of following good coding styles/practices.

• Write detailed comments. This will be very useful later for you yourself or other people who read your code.

• Use descriptive variable names for variable etc. rather than short, generic names like i, j, k. This will help your code more readable and comprehensible.

• Indent your code properly. Indent with tabs, not with spaces. This also makes your code easier to read.

• Use constants/variables

   for

   for values that appear at multiple places rather than hard-coding values.

Poor Coding Style

void setup(){
    //setup code
}
void loop()
       {                // Poor position for opening brace.
    int j = 100;        // Non-descriptive variable name
  analogWrite(5, j);    /*  Indented with spaces, and not aligned with the previous line.
                            Hard-coded values.
                            No comment to indicate what the line does.*/
                }       // Poor position for closing brace.

Good Coding Style

const int leftMotor = 5; // pin 5 used to control left motor of the robot
void setup(){
    //setup code
}
void loop(){
    int leftMotorSpeed = 100;
    analogWrite(leftMotor, leftMotorSpeed); // to write the analog value 100 to pin 5.
}