Ex_3.5_itob.c

/* function itob(n,s,b), that converts the integer n into a base b character representation in 
  the string s.
*/
#include<stdio.h>
#include<string.h>

#define MAXLINE 100

void itob(int n,char s[],int b);
void reverse(char s[]);

int main(void)
{
	int number,base;
	char str[MAXLINE];
	
	number=42425;
	base=16;

	itob(number,str,base);

	printf("%s",str);

	return 0;
}

void itob(int n,char s[],int b)
{
	int i,j,sign;

	if((sign=n)<0)
		n = -n;

	i = 0;

	do
	{
		j = n % b;

		s[i++] = (j <= 9)?j+'0':j+'a'-10;
	}while((n/=b)>0);

	if(sign < 0)
		s[i++]='-';
	
	s[i]='\0';
	
	reverse(s);
}

void reverse(char s[])
{
	int i,j,c;

	for(i=0,j=strlen(s)-1;i<j;i++,j--)
		c=s[i],s[i]=s[j],s[j]=c;
}