When the data you declare is an integer, use int, which is a natural number, and it is an integer to put it bluntly. For example, 1, 2, 3, 4 ... and so on are all plastic data.

When the declared data is Floating-point, use float, that is, data followed by decimal point, such as 120.00 and so on.

When the declared data are Characters (such as Chinese characters and pinyin), use char. Numbers can also be declared as char, but normal mathematical operations cannot be performed.

%d %f is a control symbol used to format input and output. If the input and output of the printf or scanf function are plastic, use %d, %f for floating-point type, %c for character and %s for string.

The landlord seems to be quite new, so am I. I have taught myself for about four months, and I feel that C language is very profound. Actually, there is everything in the book. Read it a few more times to understand. If you can't understand it for a while, skip it. Looking back, I can see it at a glance.