I have one piece like this program:
printf("%.2d", 5);
I think it should only display: 5 But it displayed: 05. Can you explain to me how it works?
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1Check this referenceJan Zahradník– Jan Zahradník2015-06-06 03:48:20 +00:00Commented Jun 6, 2015 at 3:48
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2 Answers
It is known as precision modifier which is written as .number, and has slightly different meanings for the different conversion specifiers
For floating point numbers (e.g. %f), it controls the number of digits printed after the decimal point:
printf( "%.3f", 1.2 );
will print:
1.200
If the number provided has more precision than is given, it will round. For example:
printf( "%.3f", 1.2348 );
will print:
1.235
For g and G, it will control the number of significant figures displayed. This will impact not just the value after the decimal place but the whole number.
printf( "%.3f\n%.3g\n%.3f\n%.3g\n", 100.2, 100.2, 3.1415926, 3.1415926 );
will print:
100.200 // %.3f, putting 3 decimal places always
100 // %.3g, putting 3 significant figures
3.142 // %.3f, putting 3 decimal places again
3.14 // %.3g, putting 3 significant figures
For integers, on the other hand, the precision it controls the minimum number of digits printed:
printf( "%.3d", 10 );
will print:
010
Finally, for strings, the precision controls the maximum length of the string displayed:
printf( "%.5s\n", "abcdefg" );
will print:
abcde
Source: Printf Format Strings
Comments
The 2 in "%.2d" means you want to print at least 2 digits. Similarly, if you wanted to print at least 3 digits, you could use "%.3d". If you wanted no additional digits (ie. no padding with 0's), you could use "%d" on its own.
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