Programming Basics (C++ and Blocks)

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

/*
   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 = 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)

• Definition (typically done by the library vendor)

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

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.

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.