Why cant I enter a number with decimal point in scanf? in C

Question

I'm writing a simple C program to classfiy distances into certain ranges such as short long or medium I understand that C will cancel out numbers after the decimal point to store as an int. So that confuses me that why can't I type in a number such as 7.5 during scanf? as that will leads me to error.

Why can't it just read in as 7 into my scanf? Is it because a keystroke of "." simply couldnt be accepted in declaring an int variable? Why is it exactly?

`scanf` stops at the first character that can't be part of the number. So it will just read in the 7, and will leave everything else for the next `scanf`. — user3386109, May 28 '14 at 04:36
You should show code snippet too, and explain just kind of error it leads you to. — hyde, May 28 '14 at 04:40
What do you want to read? Is it only 7 and 5 and the input pattern only looks like this? If so, then it can be done. — Rikayan Bandyopadhyay, May 28 '14 at 04:43

score 4 · Accepted Answer · answered May 28 '14 at 04:48

I guess you mean 7.5 rather than 7+.+5.

This is just the way the scanf function works. When you specify %d, it means "Read digits of an integer". When you specify %f,it means "Read floating point value". The documentation for scanf gives the full detail about what is read and what stops.

If you want to read values with decimals and ignore the decimal, you have many options:

Read a double and convert to int afterwards
Read an int and check for a following . ; read another int if you find one
don't use scanf; read a string and do your own parsing
etc.

Personally I'd prefer not to use scanf, it has unavoidable UB when reading integral or floating point values.

Why cant I enter a number with decimal point in scanf? in C

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