Error of finding the area of a circle in the C language

If you define r as int, enter 10000 and that will automatically force the type conversion when multiplied.

If r is defined as double, the significant digit accuracy of 10000 is not high enough.

You can try not to change the type of r, and then instead of typing r, you can specify r= directly.

The vast majority of decimals in the computer are imprecise, because all the numbers in the computer are represented by the complement of binary, for example, in the computer will be automatically converted to binary, as for the exact number of digits is related to the defined type, if it is float, the output will be accurate to 7 decimal places.

The reason for this has been answered by wangfan2000 students.

The double type precision is 8 bits, remember yes.

The value of r is too large, causing s to be out of range, try with a small number.

In the classic double problem, the data stored by the double is not the same as what you see. It is error-free. Try defining r as integer

Note that the final result of the operation with different precision follows the high precision, so the result is like this, please refer to the section of the book "Mixing Actions between Various Types of Numerical Data" for details.

Problems with data type accuracy differences and type coercion. The two upstairs spoke very well and should be praised.

3 All (1) In terms of thinking, there is no problem.

2) Logically, pi is generally taken as a decimal place, and if you define an int type, then it is very imprecise.

3) In the final output statement, there are 4 formatters in the first double quotation marks, and only 3 variables in the back, which is inconsistent.

Suggestions for modification: 1) Define the variables pi and radius r as float type (floating-point type, that is, it can be a decimal number), and the return value of the function for calculating the area is also defined as float type.

2) Then the formatter corresponding to the float type is %f, which has been modified in scanf and printf.

3) In the final output statement, complete the following variables, as follows:

printf("area = %.2f * 2f * 2f = %.2f ",pi,r,r,area);

%.2f means the number of output, with 2 decimal places left.

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