Floating Point Standard

so if you print a float as int in C
does it give random value?
ignore decimal?
error? garbage?

how float is stored in C

floats are stored in IEEE 754 format.

wait what is IEEE 754??

basically it’s a standard way to represent floating point numbers in binary.
it splits the 32 bits into:

• 1 bit for sign
• 8 bits for exponent
• 23 bits for fraction (mantissa)

Detailed IEEE 754 Explaination

why not just follow int way?

computer only understands 0s and 1s.

with 32 bits, an unsigned int can store from 0 to 2^32 - 1 = 4294967295.

but floats are trickier — between 1 and 10 alone, there are infinite decimal numbers.
we can’t just shove them into int slots.

so IEEE 754 came in and said:
"yo, let’s use scientific notation in binary (like 1.xxx * 2^n) so we can cover a huge range, not just whole numbers."

example

#include <stdio.h>

int main() {
  printf("Hello World\n");
  float radius;
  scanf("%f", &radius);
  printf("%i", radius);   // printing float as int
  return 0;
}

output

Hello World
3.14
1078523331

why that weird number?

• 3.14 as a float is stored in memory as: 👉 0x4048F5C3 (check here)

• when you do printf("%i", radius), printf thinks it’s an int and just reinterprets those raw 32 bits.

• 0x4048F5C3 in decimal = 1078523331 (check hex to decimal)

so nope, it’s not random. it’s just the float’s bit pattern being read as an int.

conclusion

printing float as int doesn’t give garbage, it gives the integer value of the float’s IEEE 754 raw bits.

use:

• %f → float
• %lf → double
• %i or %d → int

otherwise, you’ll get numbers like 1078523331 popping up 😅