2010년 10월 18일 월요일 (실수 : 지수부 & 가수부 계산)

int A = 0x12345678;
7	8	5	6	3	4	1	2
little indian

 

unsigned int A = 0x12345678; unsigned short *SP = (short*)&A unsigned char *CP = (char*)&A   printf(“%x\n”, *SP); ☜ 5678 출력 printf(“%x\n”, *CP); ☜ 78 출력

992 1000 CP 996 1000 SP 1000 7 8 5 6 3 4 1 2 A   add   변 ress 메모리(4byte)  수

41c8 000016 = 0100 0001 1100 1000 0000 0000 0000 00002
then we break it down into three parts; sign bit, exponent and significand.
Sign bit: 0
Exponent: 1000 00112 = 8316 = 131
Significand: 100 1000 0000 0000 0000 00002 = 48000016
We then add the implicit 24th bit to the significand
Significand: 1100 1000 0000 0000 0000 00002 = C8000016
and decode the exponent value by subtracting 127
Raw exponent: 8316 = 131
Decoded exponent: 131 - 127 = 4
Each of the 24 bits of the significand, bit 23 to bit 0, represents a value, starting at 1 and halves for each bit, as follows
bit 23 = 1
bit 22 = 0.5
bit 21 = 0.25
bit 20 = 0.125
bit 19 = 0.0625
.
.
bit  0 = 0.00000011920928955078125
The significand in this example has three bits set, bit 23, bit 22 and bit 19. We can now decode the significand by adding the values represented by these bits.
Decoded significand: 1 + 0.5 + 0.0625 = 1.5625 = C80000/223
Then we need to multiply with the base, 2, to the power of the exponent to get the final result
1.5625 × 24 = 25
Thus
41c8 0000   = 25