Re: My brain's getting rusty - binary conversion

[Cosmin HALMAGI <hcosmin@ss.pub.ro>]

On Tue, 1 Jul 1980, Lionel Pinkhard wrote:

> Hi,
> 
> I'm sorry, my brain seems to be getting a bit rusty. I've been working 
all day trying to write a simple program to convert a binary number into 
decimal. I tried inputting the number with 'cin', multiplying each 
digit by 128, 64, 32, 16, 8, 4, 2, 1, respectively, and then 
outputting it with 'cout', but every time I get another number than if 
I convert it by hand. Now I know my conversion (by hand) may be incorrect, 
but I don't think that 00000001 should be equal to 0. Another problem is 
that my code is pretty long. Can somebody please give me a short 
formula for doing this translation, in either C, C++, Fortran 77 
or Linux Assembler? Another language would also do fine if you tell me where 
to get a compiler and some tutorials on how to use it. :-) I also have 
Chipmunk Basic, but I know how limited Basic is.
> 
> Also, if somebody could give me a formula for translating from decimal to 
binary, I would be grateful. I know this is much more trickier, and I have no 
idea how to use either powers or square roots in C++. If somebody would tell 
me this, it would also help.
> 
> Kind regards,
> 
> Lionel Pinkhard
> =================================================================

How about (I think they work) :

//bin2dec
char c[sizeof(unsingned long)*8+1],i;//number to convert
unsigned long result=0;
for(i=0;i<sizeof(unsigned long)*8;i++){
   result=result<<1; 
   if(c[i]!='0')result+=1;
   }

//dec2bin
unsigned long number;//number to convert
char result[sizeof(unsinged long)*8+1],i;
for(i=sizeof(unsigned long)*8-1;i>=0;i--){
   {
   if(number&1==1)result[i]='1';else
                  result[i]='0';
   number=number>>1;
   }
result[sizeof(unsigned long)*8]=0;

Hope this helps,
Cosmin.


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