What is c printf %f default precision?

Question

I'm curious:

If you do a printf("%f", number); what is the precision of the statement? I.e. How many decimal places will show up? Is this compiler dependent?

This is actually defined by the C standard. I've added a tag. — , Jul 30 '09 at 16:39

score 33 · Accepted Answer · edited Sep 12 '17 at 01:17

33

The ANSI C standard, in section 7.19.6.1, says this about the f format specifier:

If the precision is missing, 6 digits are given

edited Sep 12 '17 at 01:17

sffc

answered Jul 30 '09 at 16:47

score 9 · Answer 2 · answered Jul 30 '09 at 16:52

The book, C: A Reference Manual states that if no precision is specified then the default precision is 6 (i.e. 6 digits after the decimal point).

One caveat is if the number is inf (i.e. 1.0/0.0) or NaN then C99 specifies that the output should be inf, -inf, infinity, -infinity, or nan etc....

score 7 · Answer 3 · answered Jul 30 '09 at 16:50

7

The default precision for %f is 6 digits (see ISO C99 specification, 7.19.6.1/7).

answered Jul 30 '09 at 16:50

Pavel Minaev

3 Answers3