Question on datatypes

Question

First example:

long value = 234L;

Console.WriteLine(value);

Q: Why should we give 234L instead of 234? Anyway the datatype is long. then why is L needed at the end of 234?

second example:

double d = 0.1f; Console.WriteLine(d);

float c = 0.1f; Console.WriteLine(c);

Q: Why is f required after 0.1 in both cases ? Main doubt is "f" is called float. Since the data type is float,Why f needs to be put after 0.1 ?