Convert binary to decimal

[Saint Nick]

I can figure out how to convert decimal to binary using mathmatical calculations, but for some reason I can't figure out how to work backwards.

123 is 1111011 in binary.

1 means it has a remainder, 0 means it doesn't (I'm sure you would have figured this out.)

123 / 2 = 1
61 / 2 = 1
30 / 2 = 0
15 / 2 = 1
7 / 2 = 1
3 / 2 = 1
1 / 2 = 1

So how do I work this backwards?

 

[SamurAchzar]

Iterate over all binary digits, for each '1' add 2^N to the sum, where N is the place of the digit (from right to left - LSB to MSB), counting from 0.

So in your case that would be
1: 2^0 +
1: 2^1 +
0:
1: 2^3 +
1: 2^4 +
1: 2^5 +
1: 2^6
-------
123

 

[Marthisdil]

I always remembered to just label the columns


128 64 32 16 8 4 2 1

Filling in from right to left (because it's binary)

1 1 1 1 0 1 1

Every place there's a 1, you add it's base to - 64 + 32 + 16 + 8 + 2 + 1 = 123

M

 

[Marthisdil]

I always remembered to just label the columns

128   64   32   16   8   4   2   1

Filling in from right to left (because it's binary)

         1     1     1    1   0   1   1

Every place there's a 1, you add it's base to - 64 + 32 + 16 + 8 + 2 + 1 = 123

M

 

[SamurAchzar]

That's what I always do too - but it's not educational to tell people that straight up 😀

 

[Saint Nick]

Well, long story short, I am supposed to write a C++ program that converts up to a fifteen digit binary number into a decimal number. It doesn't have to validate the information or anything, just assuming that the user enters 1s and 0s and only up to 15 of them total. I can't figure out how to do it. This helped, but everything I've tried thus far (code-wise of course) has done me no good.

bleh . . . why am I a comp sci major?

 

[jakalsucks]

Forgive me, I haven't written in C++ in a very long time. I understand the syntax isn't anywhere near right.

for(intCounterX = 0; intCounterX < strTemp.Length; intCounterX++)
{
intTotal = (intTotal << 1) + (int)strTemp[intCounterX] - 48
}

That last post I made was complete rubish.

 

[BrownTown]

getting peopel to do your homwwork for you isnt exactly highly technical, especially when it only requires a loop with 1 line of code...

 

[Vegitto]

Originally posted by: jndietz
Well, long story short, I am supposed to write a C++ program that converts up to a fifteen digit binary number into a decimal number. It doesn't have to validate the information or anything, just assuming that the user enters 1s and 0s and only up to 15 of them total. I can't figure out how to do it. This helped, but everything I've tried thus far (code-wise of course) has done me no good.

bleh . . . why am I a comp sci major?

I don't know any C(+/++), but why don't you just use a language in between? Like, when you want to BabelFish something from French to English, the engine translates the French to Esperanto, and the Esperanto to English. Maybe binary > hex > decimal?

 

[BassBomb]

i have lost all my knowledge from grade 11 when i learned this

but id use my Sharp DAL calc to convert if i needed to 😛