# binary to decimal using array

Okay i'm not that great at C++ as you will see from how far i got until i hit a wall.

The problem is this

Allows the user to input a series of 0's and 1's which will be stored as an array representing a binary word. Input should stop when something other than a 0 or a 1 is input by the user and display the decimal equivalent.

To convert i think i got the concept but i just cant seem to implement it

binary 11010

take each number individually and multiply it by 2 to the power of the placement of the number - 1.

(1*2^4)+(1*2^3)+(0*2^2)+(1*2^1)+(0*2^0) = 26

so i had a crack at it

[code]#include
#include
using namespace std;

void main ()
{
int power;
char binary [16],*p; //array size declared
p=binary;

cout<<"Enter binary input(1's & 0's):";

cin>>binary;

cout<<"
Binary Input is:"<<binary<<endl; //display array output

for (power=strlen(binary)-1;power>-1; power--) //calculates the power

cout<<power<<endl; //test output
}
[/code]

i'm sure there need to be another loop to retrieve the array values. then its a simple task of calculating the output

sum + = binary[i] * pow(2, power)

This is probably easy but i have been working on my other units and made the mistake of assuming it was easier then it looked

rumon

• : Okay i'm not that great at C++ as you will see from how far i got
: until i hit a wall.
:
: The problem is this
:
: Allows the user to input a series of 0's and 1's which will be
: stored as an array representing a binary word. Input should stop
: when something other than a 0 or a 1 is input by the user and
: display the decimal equivalent.
:
: To convert i think i got the concept but i just cant seem to
: implement it
:
: binary 11010
:
: take each number individually and multiply it by 2 to the power of
: the placement of the number - 1.
:
: so you start with the number far left and move right:
:
: (1*2^4)+(1*2^3)+(0*2^2)+(1*2^1)+(0*2^0) = 26
:
: so i had a crack at it
:
: [code]: #include
: #include
: using namespace std;
:
: void main ()
: {
: int power;
: char binary [16],*p; //array size declared
: p=binary;
:
: cout<<"Enter binary input(1's & 0's):";
:
: cin>>binary;
:
: cout<<"
Binary Input is:"<<binary<<endl; //display array output
:
: for (power=strlen(binary)-1;power>-1; power--) //calculates the power
:
: cout<<power<<endl; //test output
: }
: [/code]:
:
:
: i'm sure there need to be another loop to retrieve the array values.
: then its a simple task of calculating the output
:
: sum + = binary[i] * pow(2, power)
:
:
: This is probably easy but i have been working on my other units and
: made the mistake of assuming it was easier then it looked
:
: rumon
:
:

There seems to be a better way. Ru through the array (use another pointer *x, not any extra vars) until you hit a value you don't want. Then use a loop (i) from 0 till you reach the beginning (old *p), and as it increments use pow(2,i). don't use binary[i], use sum += *x * pow(power,i).

Doubts?

• : There seems to be a better way. Ru through the array (use another
: pointer *x, not any extra vars) until you hit a value you don't
: want. Then use a loop (i) from 0 till you reach the beginning (old
: *p), and as it increments use pow(2,i). don't use binary[i], use sum
: += *x * pow(power,i).
:
: Doubts?
:
:
: Thank you for the post. How exactly would i implement a second pointer?
would it be

char binary [16], *p,*x;
p=binary;
x=p;

not quite sure on how its going to use the 2 points to convert to decimal.

• :
: : There seems to be a better way. Ru through the array (use another
: : pointer *x, not any extra vars) until you hit a value you don't
: : want. Then use a loop (i) from 0 till you reach the beginning (old
: : *p), and as it increments use pow(2,i). don't use binary[i], use sum
: : += *x * pow(power,i).
: :
: : Doubts?
: :
: :
: : Thank you for the post. How exactly would i implement a second pointer?
: would it be
:
: char binary [16], *p,*x;
: p=binary;
: x=p;
:
: not quite sure on how its going to use the 2 points to convert to
: decimal.
:
:
You're right in the code, almost.
Sorry, I wanted to post the full code, I've done this before, but I haven't got much time, I'm on a tight schedule.

You just equalise the two pointers by [code]x = p;[/code];
then run the array till the end with [code]while(*x++ < 2) ;[/code];
Then using a for loop and a variable i, [code]for(i=0;x!=p;i++,x--)[/code]
You can implement the algorithm using [code]sum == *x * pow(2,i);[/code]
• [color=Blue]
This seems way more complex than it is needed. pow() also kind of slow. All what is needed here is to have a mask of bits, like that one: 0000 0000 0000 0000 0001. Then begin from the end of the input string checking for '0' and '1' characters. If '1' is entered, then OR that mask with a result variable (which is zero at the beginning of this loop). When looking at the next character - mask also shifts LEFT by one bit:
[/color]
[code]
unsigned int BinaryStringToHex32 (char* s)
{
int nBits = strlen (s);
unsigned int result = 0;

s += nBits;
while (nBits--)
{
s--;
if (*s == '1') result |= mask;
}
return result;
}
[/code]
• HrishiOA007, AsmGuru62 Thank you for helping out a first year student ^^ with his C++ homework really appreciate it. Got java second semester lesson learn. Got to dedicate a little more to getting my head around the programming language.

anyway thanks again, really help out
• : HrishiOA007, AsmGuru62 Thank you for helping out a first year
: student ^^ with his C++ homework really appreciate it. Got java
: second semester lesson learn. Got to dedicate a little more to
: getting my head around the programming language.
:
: anyway thanks again, really help out
:
Anytime, man.......
And ASMGuru, I was just trying to tell this first year student, not a boolean master. Frankly, even I've had problems earlier with MASKS and bitmaps in VC++. Who cares for speed with today's processors? Its a few instructions more or less in such small programs...
• : : HrishiOA007, AsmGuru62 Thank you for helping out a first year
: : student ^^ with his C++ homework really appreciate it. Got java
: : second semester lesson learn. Got to dedicate a little more to
: : getting my head around the programming language.
: :
: : anyway thanks again, really help out
: :
: Anytime, man.......
: And ASMGuru, I was just trying to tell this first year student, not
: a boolean master. Frankly, even I've had problems earlier with MASKS
: and bitmaps in VC++. Who cares for speed with today's processors?
: Its a few instructions more or less in such small programs...
:
[color=Blue]I agree, of course.

My apologies...
It's just when I see a lot of CPU cycles spent - I always want to point the better solution.

• What say you guys to this version:

[code]
#include
#include

int main()
{
char *input="10110112";
int i=0, j=0;

while (i<strlen(input) && (input[i]=='1' || input[i]=='0'))
j=j*2+(input[i++]-48);

printf("The decimal equivalent is %d.

", j);

system("PAUSE");
return EXIT_SUCCESS;
}
[/code]

Take Care,
Ed
• : What say you guys to this version:
:
: [code]:
: #include
: #include
:
: int main()
: {
: char *input="10110112";
: int i=0, j=0;
:
: while (i<strlen(input) && (input[i]=='1' || input[i]=='0'))
: j=j*2+(input[i++]-48);
:
: printf("The decimal equivalent is %d.

", j);
:
:
: system("PAUSE");
: return EXIT_SUCCESS;
: }
: [/code]:
:
: Take Care,
: Ed
:

Good, but you won't get a null character terminated string during input
unless you use strin. Nice work!!
• [color=Blue]strlen() in a loop. ..mmm... sweet cycles... :-)[/color]
• Actually, I had noticed, but didn't address the following wording of the OP's original problem:

"Input should stop when something other than a 0 or a 1 is input by the user and display the decimal equivalent."

I read that as each input character being processed at each keystroke. However, there isn't any standard way to do that and the above answers didn't address it, so neither did I.

My compiler accepts getch() from the conio.h file, so I would address the above in this manner:

[code]
#include
#include

int main()
{
int i, j=0;

do{
i=getch();
printf("%c", i);
if (i=='1' || i=='0')
j=j*2+(i-48);
} while (i=='1' || i=='0');

printf("

The decimal equivalent is %d.

", j);

system("PAUSE");
return EXIT_SUCCESS;
}
[/code]
What would be the "standard" equivalent?

Take Care,
Ed