%d %c and %s are data specifiers used in C programming. It specifies what data type that is being used in order to input and/or output the exact thing that you expected.
%d is for integers %c is for single character %s is for strings.
Not sure in what environment your asking for, but in C programming, %d is an integer (basically a number), %c is a character, that is a single alphanumeric character, where as %s is a series of alphanumeric characters, in programming %s is actually just an array of characters (so multiple %c), but don't worry about that to much.
Examples in c.
int number = 1; char character = "c"; (numbers (integers) can be characters) char string[5] = "abcd"; ([5] implies 5 characters, here there are 4, that is because an invisible character exists known as a "null terminator" (\0).
The flashing yellow light indicates that people should be aware of other cars and turn carefully. To be more safe, you should slightly slow down, make sure all signals that should be on are on, and you should drive very carefully.
