Extracting an 4 digit int (decimal) into string in C manually - c

Question

I'm struggling with this programming assignment I have for one of my classes here. I'm an electrical engineering student so my programming is by no means amazing. I'm told to write a c program that takes a 12-bit number and extracts each of that 12 bit number's digits into a char array. I did the quick math and realized that the largest number we can obtain is 0xFFF or 4095 in decimal. I found an algorithm that I thought would work quite well but for some reason, my code isn't doing what I thought. I am continuing to try and troubleshoot this, but with my only way to run it being linux terminal window, I don't have a great debugging utility to step through the program. Any help would be greatly appreciated. Feel free to ask some questions as well and I'll do my best to field them. I am not a fluent programmer so bear that in mind. Also, if someone could explain integer division to me that would be helpful. I was under the assumption that something like 8/10 would return a result of 0 but I don't know that it's working that way when I run the program. Thank you.
I CANNOT USE FUNCTIONS TO DO THIS AND MUST DO IT MANUALLY.
Here is what I have thus far.
Attempt # Solution:
//12 bit value into string of decimal chars
//EX: 129 -> a '1' a '2' and a '9'
void main (void) {
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stddef.h>
//Initialize an array with 5 spaces, each space
//holds one character (accounts for largest number 4095)
char OUT[5];
uint8_t length = sizeof(char);
//Isolating each int value happens here
//initialize i to act as a counter to loop through array
uint8_t i=2;
//Initialize an input value to test the code;
uint16_t IN=549;
while (IN/10 > 0)
{
OUT[length-(i+1)] = '0' + (IN%10);
IN=IN/10;
if (IN <= 10)
{
if (IN = 10)
{
OUT[length-(i+1)] ='1';
//fixes infinite loop issue
IN=0;
}
else
{
OUT[length-(i+1)] ='0' + IN;
//fixes infinite loop issue
IN=0;
}
}
//Increment Counter to keep track of char array
i++;
}
//add the new line at the end of the array of chars
OUT[length-1]='\n';
printf("String is -> %s", OUT);
}
Couple of notes:
Using IN%10 is part of the algorithm that isolates the furthest right digit in decimal. I had to add some "fudge factors" to my counter to get the array to line up properly and account for the \n at the end of my char array. The conditional statements that I put inside my while loop were to catch some edge cases (mainly when IN became 10 or less).

Answer 1

It looks like you are bending over backwards to handle the fact that you have to print the leftmost character first. The logic is much simpler if you just generate the rightmost character first and then reverse it.
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stddef.h>
#include <string.h>
//12 bit value into string of decimal chars
//EX: 129 -> a '1' a '2' and a '9'
void main (void) {
char OUT[5];
memset(OUT, 0, 5);
int i=0;
int j;
uint16_t IN=549;
// Generate the string in reverse order.
while (IN != 0)
{
OUT[i++] = '0' + (IN%10);
IN/=10;
}
// Reverse the string
for (j = 0; j < i/2; j++) {
char temp = OUT[j];
OUT[j] = OUT[i-1-j];
OUT[i-1-j] = temp;
}
printf("String is -> %s\n", OUT);
}

Answer 2

This line is your problem:
uint8_t length = sizeof(char);
The sizeof function returns the size of the type between parentheses. In this case it returns 1, because a char is a 1 byte variable. Then when you try to access the elements of the array you get a negative number from length-(i+1).

Answer 3

Here is my final solution using the more complex way in case anyone is curious/stumbles into the problem later on.
void main (void) {
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stddef.h>
//Initialize an array with 5 spaces, each space holds one character (accounts for largest number 4095)
char OUT[5];
OUT[0] = '0';
OUT[1] = '0';
OUT[2] = '0';
OUT[3] = '0';
OUT[4] = '0';
uint8_t length =5; //sizeof(char) was giving me an error and thus not used.;
//Isolating each int value happens here
//initialize i to act as a counter to loop through array
uint8_t i=2;
//Initialize an input value to test the code;
uint16_t IN=4012;
//Initialize variable for % operator value
uint16_t mod=0;
while (IN/10 > 0)
{
mod=IN%10;
OUT[length-i] = '0' + mod;
IN=IN/10;
if (IN <= 10)
{
if (IN == 10)
{
OUT[length-(i+2)] ='1';
OUT[length-(i+1)] ='0';
//fixes infinite loop issue
IN=0;
}
else
{
OUT[length-(i+1)] ='0' + IN;
//fixes infinite loop issue
IN=0;
}
}
//Increment Counter to keep track of char array
i++;
}
//add the new line at the end of the array of chars
OUT[length-1]='\n';
printf("String is -> %s", OUT);
}