double and float

[goelvivek]

#include<stdio.h>
#include<conio.h>
void main()
{double i=1.1;
float j=1.1;
clrscr();
if(i==j)
printf("both are equal");
else
printf("both are not equal");
getch();}


why i am getting the else statement as output if the value in double and float data type are equal but if we compare them then the output we get is that the no are equal

[Ganon11]

Please see Floating Point Arithmetic here.

[ruskalym]

Your numbers are not equal because it is not stored in decimal form but in binary form. Read IEEE 754 standard specification for details.

To compare two floating point numbers, you have to fix a precision delta value.

if (fabs(i - j) < 0.000001) { ... // almost equal }

[weaknessforcats]

Also, be aware of this:

float j=1.1;

Symbolic constants like 1.1 are double. A double is larger than a float so your compiler is giving you a warning about truncation and possible loss of data as the double is converted to a float.

You should create the constant as a float by coding:

float j = 1.1f;    /* or 1.1F */
 

Further, float is a type developed in the years of computers with small memories. Unless you can write a specific reason on paper as to why you need a float, I recommend you use double throughout.