Thread: Need help on functions

Here is a start. You may want to check out the FAQ.

Code:

#include <stdio.h>
#include <stdlib.h>

unsigned long int B2U(char *bits)
{
   return strtoul(bits, NULL, 2);
}

signed long int B2S(char *bits)
{
   return strtol(bits, NULL, 2);
}

int main(void)
{
   char v[] = "11010101";
   printf("B2U(\"%s\") = %lu\n", v, B2U(v));
   printf("B2S(\"%s\") = %ld\n", v, B2S(v));
   return 0;
}

/* my output
B2U("11010101") = 213
B2S("11010101") = 213
*/

This is not a homework service.
http://cboard.cprogramming.com/annou...p?s=&forumid=4

Now, it's your turn to post an attempt.

Have you tried a search?

Your original question asked how to write a function. I showed a basic shell from which to begin.

oh yea..functions should be implemented using only arithmetic or logical operations. You should not use any library functions (e.g. sprintf, atoi, etc.) which is harder..=*(

This type of "request" implies you want it done for you.


Are you saying you have no idea how to convert the text representation of a digit into a number?

Code:

char digit = '4';
int number = digit - '0';

Or that you don't understand binary arithmetic?

I'm not trying to be argumentative or condescending. I'm just trying to prod you into thinking a little bit about the problem you are trying to solve.

If you can be a little more specific about what you don't understand, replies can address these issues much better. "I don't know anything" tends to mean "do it all". Unless you can disprove this assumption by demonstrating -- by posting an attempt -- that you understand some things, your posts are very likely to be interpreted this way.

And if you choose not to post any attempts, learn to fine-tune your use of search engines.

>> ...since my teacher gave us none.

Go get a good C programming book, and work through each chapter, one by one. Self-taught programming. What a concept!

The routines will be identical except for the return value.

First zero the return value.

Take the characters one at a time from the left. Convert them into binary by subtracting the ASCII value of '0' into a temp variable.

Then shift the return value left by 1 bit using the << operator. OR the temp variable into the return value using the | operator.

Continue for each character in the array.