How To Fix Segmentation Fault 11 in a C program? - c

Question

I am new to C programming. I'm writing a function that converts an integer into hexadecimal.
For some reason, I am getting a segmentation fault 11. Please advise. Thank you!
Here is the code for my function:
it converts the integer to binary first
adds 0s where it is needed so binary length would be multiples of 4
reverses the order of the binary
converts every 4 numbers into hexadecimal
void printHexadecimalForm( int X )
//Purpose: Print parameter X in hexadecimal form
//Output: Hexadecimal representation of X directly printed
//Assumption: X is non-negative (i.e. >= 0)
{
//[TODO] CHANGE this to your solution.
int input = X;
int output[32];
int i = 0;
while(input != 0){
if(input%2 != 0){
input = input - 1;
input /= 2;
output[i] = 1;
i++;
}
else{
input /= 2;
output[i] = 0;
i++;
}
}
while(i % 4 != 0){
output[i + 1] = 0;
i++;
}
for (int j = 0; j < i/2; j++)
{
int temp = output[j];
output[j] = output[i - 1 - j];
output[i - 1 - j] = temp;
}
int c, k = 0;
for(int z = 0; z < i; z += 4; ){
for (c = z; c < c + 4; c++){
k = 10 * k + output[c];
}
if(k == 0000){
printf("%d",0);
}
if(k == 0001){
printf("%d",1);
}
if(k == 0010){
printf("%d",2);
}
if(k == 0011){
printf("%d",3);
}
if(k == 0100){
printf("%d",4);
}
if(k == 0101){
printf("%d",5);
}
if(k == 0110){
printf("%d",6);
}
if(k == 0111){
printf("%d",7);
}
if(k == 1000){
printf("%d",8);
}
if(k == 1001){
printf("%d",9);
}
if(k == 1010){
printf("%c", 'A');
}
if(k == 1011){
printf("%c", 'B');
}
if(k == 1100){
printf("%c", 'C');
}
if(k == 1101){
printf("%c", 'D');
}
if(k == 1110){
printf("%c", 'E');
}
if(k == 1111){
printf("%c", 'F');
}
}
}

Answer 1

I suggest you to take deep breath and start all over again. First remember, there's no need to convert anything to binary. Everything is binary already.
Maybe this little piece, which retrieves two hexadecimal characters could help you to get on to the track: (this is just one method)
int n = 165; // this is the number we want to display in hex (165 is 0xa5)
int i, hexChar;
i = n & 0xF; // bitwise AND with 00...001111
if(i < 10) // look up to ASCII table for more info
hexChar = i + 48; // character '0' is code 48, '1' is 49 etc.
else
hexChar = i + 55; // character 'A' is code 65, 'B' is 66 etc.
printf("Rigth most hex: %c\n", hexChar);
i = n >> 4; // shift all bits 4 steps to the right
i = i & 0xF; // bitwise AND with 00...001111
if(i < 10) // look up to ASCII table for more info
hexChar = i + 48; // character '0' is code 48, '1' is 49 etc.
else
hexChar = i + 55; // character 'A' is code 65, 'B' is 66 etc.
printf("Second hex: %c\n", hexChar);