In fact, in today's computers, a 32-bit compiler is usually used (unless you also use Turbo C). At this time, there is no difference between int and long. (4 bytes in all, representing the range from -2 147483648 to 2 147483647)B is not written in L, and the default value is int. C and d are both real numbers.

Sometimes, you will see that in some old codes, some integers are often followed by an uppercase or lowercase L letter. What does this mean? It turns out that if the range of a constant allows, the computer will think it is an int type by default, so to make the computer think that a number is a long int type, you can add L or L after it. However, this only makes sense on the previous 16-bit machine. Now our machines are all 32-bit, and long int and int are exactly the same, both of which occupy 4 bytes, so there is no need to use them like this. However, when defining a constant of type long long, it is necessary to write 3LL, and unsigned long long is 3LL.