In C, how to convert an integer to binary?

There is no standard function in C to convert or display an integer in its binary form. However, some libraries (quite rare) implement the %b format code which allows to display an integer in binary form:

// Display 100 on some environments
printf ("%b", 4);

If you need to convert an integer to binary, then you will have to write a dedicated function. Depending on your needs, select one of the following options:

• In C, how to write a function that displays an integer in binary?
• In C, how do you write a function that converts an integer to binary (into another integer)?
• In C, how do you write a function that converts an integer to binary in a string?
• With Arduino, how to display an integer in binary ?