Reading in double values with scanf in c

问题

I try to read-in 2 values using scanf() in C, but the values the system writes into memory are not equal to my entered values. Here is the code:

double a,b;
printf(\"--------\\n\"); //seperate lines
scanf(\"%ld\",&a);
printf(\"--------\\n\"); 
scanf(\"%ld\",&b);
printf(\"%d %d\",a,b);

If I enter 1 and 2, CMD returns a correct, but b = -858993460 Here is what I already tried: using float or int instead of double, using scanf_s, using scanf(\"%d or %f for %i or %li or %lf or %e or %g ), using fflush(stdin) to clear keyboard buffer, reading in b first, trying like all possible combinations. I found out that there is a problem with the length of double on 32 bit OS, so that you are forced to use scanf(\"%lf\", &f) to read in a double. No matter what I do, second value is always wrong.

I use MS VS express 2012 for Desktop on Windows 7 32 bit OS.

回答1:

Use the %lf format specifier to read a double:

double a;
scanf("%lf",&a);

Wikipedia has a decent reference for available format specifiers.

You'll need to use the %lf format specifier to print out the results as well:

printf("%lf %lf",a,b);

回答2:

As far as i know %d means decadic which is number without decimal point. if you want to load double value, use %lf conversion (long float). for printf your values are wrong for same reason, %d is used only for integer (and possibly chars if you know what you are doing) numbers.

Example:

double a,b;
printf("--------\n"); //seperate lines
scanf("%lf",&a);
printf("--------\n"); 
scanf("%lf",&b);
printf("%lf %lf",a,b);

回答3:

You are using wrong formatting sequence for double, you should use %lf instead of %ld:

double a;
scanf("%lf",&a);

回答4:

Format specifier in printf should be %f for doubl datatypes since float datatyles eventually convert to double datatypes inside printf.

There is no provision to print float data. Please find the discussion here : Correct format specifier for double in printf

回答5:

Using %lf will help you in solving this problem.

Use :

scanf("%lf",&doub)

来源：https://stackoverflow.com/questions/13730188/reading-in-double-values-with-scanf-in-c

标签

scanf

conversion-specifier