Convert (10.1101) binary to decimal
Convert (10.1101) binary to decimal
EDIT:Code:#include <stdio.h> #include <math.h> #include <string.h> int main( void ) { char *bitstring = "10.1101"; int decimalPoint = 0; /* Location of decimal */ int i = 0; /* Counter1 */ int j = 0; /* Counter2 */ double value = 0.00; /* Locate decimal point */ for( i = 0; i < strlen(bitstring); i++ ) { if( bitstring[i] == '.' ) { decimalPoint = i; break; } } /* Calculate exponent */ for( i += 1, j = 1; i < strlen(bitstring); i++, j++ ) { if( bitstring[i] == '1' ) { value += (double)(1.00 / (double)pow(2.00,(double)j)); } } /* Calculate Mantissa */ for( i = decimalPoint-1, j = 0; i >= 0; i--, j++ ) { if( bitstring[i] == '1' ) { value += (double)pow(2.00,(double)j); } } printf("%s = %f\n", bitstring, value); return 0; }
Sorry I'll explain it a little..
The bitstring is a series of 1's and 0's, the delimiter between the mantissa and exponent being the decimal point.
Step 1: You need to find the location of the decimal point, and you also need to know the location of the LSB of the mantiisa - so you do this.
Step 2: You've found the decimal, set i to decimalPoint and decrement i to point to the LSB of the mantissa and begin calculating powers. You start with i = 0 and (2^i)*bit and as you move towards the MSB you increment t i by 1. So you have the summation of( 2^i)*bit where i = (decimalPoint-1) to 0.
Step 3: Now you need to exponent side of the bitstring, so you point to the next bit after the decimal. You start with i = 1 and (1.00 / (2^i))*bit to get the actual decimal value. As you move towards the LSB of the mantissa you need to increment i by 1. So you have the summation of (1.00 / (2^i)*bit, where i = 0 to strlen(bitstring)-decimalPoint.
The summation of the value obtained from step 2 and the value obtained from step 3 is your decimal value.
Last edited by saeculum; 03-12-2009 at 08:53 AM.
This converts binary numbers too:
It doesn't deal with decimals tho, and you can't convert the right side the same way I wouldn't think.Code:#include <stdio.h> #include <string.h> int main (int argc, char *argv[]) { int i, bit=1, result=0, len=strlen(argv[1]); for (i=len-1;i>=0;i--) { if (argv[1][i]!='1') { bit*=2; continue; } result|=bit; bit*=2; } printf("Binary %s is decimal %d\n",argv[1],result); return 0; }
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
Values to the left of the decimal represent powers of 2 (starting at 2 raised to the 0th power). Values to the right of the decimal represent powers of ½ (starting at ½ raised to the 1st power).
Example: 1010.0101
The values to the left of the decimal are 1010. These represent the value (1 * 2 ^ 3 + 0 * 2 ^ 2 + 1 * 2 ^ 1 + 0 * 2 ^ 0). Simplifying this you get (1 * 8 + 0 * 4 + 1 * 2 + 0 * 1) which is (8 + 2) or 10 (decimal).
The values to the right of the decimal are 0101. These represent the value (0 * ½ ^ 1 + 1 * ½ ^ 2 + 0 * ½ ^ 3 + 1 * ½ ^ 4). Simplifying this you get ( 0 * 0.5 + 1 * 0.25 + 0 * 0.125 + 1 * 0.0625) which is (0.25 + 0.0625) or 0.3125.
Combining these two you get 10.3125 as the final answer.
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Thanks hk_mp5kpdw for that. So I think this is an optimized solution:
Code:#include <stdio.h> #include <string.h> int getdot (char *string, int len) { int i; for (i=0;i<len;i++) if (string[i]=='.') return i; return len; /* no decimal places */ } int main (int argc, char *argv[]) { float result,right=0.0f, tmp; int i, ii, left=0, len=strlen(argv[1]), dot=getdot(argv[1],len), bit=1; /* integer */ for (i=dot-1;i>=0;i--) { if (argv[1][i]!='1') { bit*=2; continue; } left|=bit; bit*=2; } result=(float)left; /* integer fraction */ for (i=dot+1;i<len;i++) { if (argv[1][i]!='1') continue; tmp=0.5f; for (ii=0;ii<i-dot-1;ii++) tmp/=2; right+=tmp; } result+=right; printf("Binary %s is decimal %f\n",argv[1],result); return 0; } Example output: [root~/C] ./a.out 1010.0101 Binary 1010.0101 is decimal 10.312500
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
My homepage
Advice: Take only as directed - If symptoms persist, please see your debugger
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