Just thought I'd discuss some basics on a nice sunny morning.
When we are dealing with precision - in this case float - when it is said that float has 6 decimal digits precision - does that include the digits before the decimal point? I had assume d wrongly that it referred only to the digits after the decimal point. I am not using double here - examining float just right now.
eg. this circle example highlights this. In the printf control strings I display to 6 places.
run1Code:float radius = 0.0f; /* radius of table */ float diameter = 0.0f; float circumference = 0.0f; float area = 0.0f; float pi = 3.14159265f; printf("\nInput the diameter of the table: "); scanf("%f", &diameter); radius = diameter/2.0f; circumference = 2.0f*pi*radius; /* circumference = 2πr */ area=pi*radius*radius; /* area = π^r2 */ printf("\nThe circumference is %.6f", circumference); printf("\nThe radius is %.6f", radius); printf("\nThe area is %.6f\n", area); return 0;
Input the diameter of the table: 1.1
The circumference is 3.455752
The radius is 0.550000
The area is 0.950332 /* on my calculator it is 0.9503317 */
Input the diameter of the table: 11
The circumference is 34.557522
The radius is 5.500000
The area is 95.033180 /* on my calculator it is 0.95033176 */
In run1, the area is only accurate to 5 places after the decimal - so 0 before the decimal is part of 6 digits of precision.
In run2, the area is only accurate to 4 places after the decimal - so 95 before the decimal is part of 6 digits of precision.
I am basing these precisions on my compiler/machine version. So, having a large number before the decimal (eg 1024.4567) would drastically reduce the accuracy. Using format %.6f only would be good for floats like 0.xxxxx for example and 1024.xxyyyy would be inaccurate after 2 places beyond the decimal.