Thread: [BEGINNER] Decimal to Binary Converter help

If you compile with warnings, you should see something like the following:

Code:

/*
main.c||In function 'main':|
main.c|21|warning: statement with no effect|
||=== Build finished: 0 errors, 1 warnings ===|
*/

This is because you accidentally used == (comparison) instead of = (assignment).

In fact, as you fix up the code, you'll see the "if(modulo==0)" code isn't even necessary.

The reason you're seeing gibberish sometimes is because you break out of the loop when the number goes below 1, but all the array positions have not necessarily been filled yet. Therefore, when you attempt to print out the numbers at those indices, since they have not been initialized to anything, they contain garbage values.

Try initializing the entire array to zero. This way, anything not updated in the loop will still have an initial value.

Code:

int BitNum[8] = {0};  // initialize all elements to zero

Then, as mentioned, you want to reverse the array so it prints the bits in the correct order.

Originally Posted by Sankait Laroiya

P.S: Any suggestion about my code writing habit is really welcomed . Thanks.

I am happy to see several things about your code. Neat/consistent indentation, meaningful variable names, proper form of "main()". We don't get enough of that here from new posters. Well done!

Well, it appears to work, but not necessarily because it's correct. You have a few mistakes that are canceling each other out, with a net result of making the program give the correct output.

Let's start with the warnings again:

Code:

/*
main.c||In function 'main':|
main.c|17|warning: suggest parentheses around assignment used as truth value|
main.c|19|warning: statement with no effect|
||=== Build finished: 0 errors, 2 warnings ===|
*/

You changed the wrong operator. You had the "modulo == 0" correct (you are making a comparison); it was the "BitNum[x] == 0" that was incorrect (you want to make an assignment).

Code:

if(number<0)

This can never be true in your code, since division with positive numbers (or zero as the numerator) will never yield a negative value. So the "break" is never seen, meaning the program will loop all eight times. Since no loops are skipped, line 16 will ensure that all array indices are given a value (hence bypassing the need to initialize the array, as I originally suggested).

You're making this more complicated than it has to be. Fun fact: remove everything from your first "for()" loop except for lines 16 and 21, run it, and see what happens. Then try to figure out why that happened. I'd suggest using a pencil and paper to run through the loop "by hand", keeping track of each value each time through the loop. Analyzing code "on paper" like this will help give you a better understanding of what the code is actually doing.

Originally Posted by Matticus

Well, it appears to work, but not necessarily because it's correct. You have a few mistakes that are canceling each other out, with a net result of making the program give the correct output.

Let's start with the warnings again:

Code:

/*
main.c||In function 'main':|
main.c|17|warning: suggest parentheses around assignment used as truth value|
main.c|19|warning: statement with no effect|
||=== Build finished: 0 errors, 2 warnings ===|
*/

You changed the wrong operator. You had the "modulo == 0" correct (you are making a comparison); it was the "BitNum[x] == 0" that was incorrect (you want to make an assignment).

Code:

if(number<0)

This can never be true in your code, since division with positive numbers (or zero as the numerator) will never yield a negative value. So the "break" is never seen, meaning the program will loop all eight times. Since no loops are skipped, line 16 will ensure that all array indices are given a value (hence bypassing the need to initialize the array, as I originally suggested).

You're making this more complicated than it has to be. Fun fact: remove everything from your first "for()" loop except for lines 16 and 21, run it, and see what happens. Then try to figure out why that happened. I'd suggest using a pencil and paper to run through the loop "by hand", keeping track of each value each time through the loop. Analyzing code "on paper" like this will help give you a better understanding of what the code is actually doing.

Okay, could you please explain me this:
When a number is odd; example: number = 9 and we divide it by 2 in the for loop, how come its modulo in the next part of the loop returns a remainder (0 or 1)? What will be 4.5%2?

Thanks.

Originally Posted by laserlight

9 / 2 gives you 4, then 4 % 2 gives you 0. As for why: that's how the % operator is supposed to work, i.e., the result of the % operator is the remainder.


It will be 0.5, except that because the operands of the % operator must be integers, you will get an error instead. If you need to work with floating point, what you can do is to #include <math.h> and use fmod.

Thanks, I understood. You mean to say when float is passed to a % it leaves the digits after decimal and simply takes the absolute value, right?
And Could you also help me with this:

Code:

http://cboard.cprogramming.com/c-programming/164203-%5Bbeginner%5D-binary-decimal-converter-help.html#post1211145