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 |
|---|---|
/* multi-line comment */ // single line comment |
|
Statements
- Statements are compiled into an ‘executable’ of 1s and 0s, which are run on the Arduino.
- Statements end with a ;
| C++ | Blocks |
|---|---|
c = a+b; // c is assigned the sum of a, b |
|
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 : 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 classes)
- Variables can be declared with or without initialization
| C++ | Blocks |
|---|---|
int a; // declaration int a = 0; // declaration and initialization |  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 |
|---|---|
a = 10; // assigning 10 to a |  |
A variable value is used when it appears in a comparison or on the right-hand side of an expression/assignment.
| C++ | Blocks |
|---|---|
(a == 1) // checking if a is equal to 1 |  |
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 |
|---|---|
b = a + 10; // variable b is assigned the value of variable a plus 10. |  |
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 if-else statement. The {} is optional if there is only one line being executed conditionally for if or else.
| C++ | Blocks |
|---|---|
if(a>0){
c = a+b;
//executed when a>0
}
else{
c = a-b;
//executed when a<0 or a==0
}
|  |
To Do : Read up 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 while loop.
| C++ | Blocks |
|---|---|
while(a>0){
a = a-b;
/* executed over and over until a<0 or a==0 */
}
|  |
To Do : Read up about for loop, do-while 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.
| C++ | Blocks |
|---|---|
{
digitalWrite(11, HIGH);
}
|
|
Setup() and loop() functions
- Setup and loop are functions called automatically (unlike all other functions needs to be called explicitly)
- setup() is called once, when you release the reset button / plug in your Arduino / upload a new code onto the board
- loop() is 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 Coding Styles / Practices
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 values that appear at multiple places rather than hard-coding values.
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.
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.
}