Código: Seleccionar todo

#include<iostream>

using namespace std;

int atoi(char* string);
double atof(char* string);
unsigned int strlen(char* string);
void itoa( char* string, int n);
void reverse(char* string);

int main()
{
    char* c = (char*)"  -154.456";
    double val;
    cout << (val=atof(c)) << endl;
    itoa(c,val);
    cout << c << endl;
    cin.get();
    return 1;
}

unsigned int strlen(char* string)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    unsigned int i=0;
    while (*(string++) != '\0') i++;
    return i;
}
void reverse(char* string)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    char c;
    unsigned long int i;
    unsigned long int j;
    for ( i=0, j=strlen(string)-1; i <j; i++,j-- )
    {
        c=string[i];
        string[i]=string[j];
        string[j]=c;
    }
}
int atoi(char* string)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    return (int)atof(string);
}
double  atof(char* string)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    double n, p;
    int i, s;

    for ( i=0; string[i]==' ' || string[i]=='\n' || string[i]=='\t'; i++ );

    if ( string[i]=='+' || string[i]=='-' )
        s=(string[i++]=='+') ? 1:-1;
    else
        s=1;
    for ( n=0 ; string[i]>='0' && string[i]<='9'; i++ )
        n = 10*n+string[i]-'0';

    if (string[i]=='.')
        i++;
    for ( p=1 ; string[i]>='0' && string[i]<='9'; i++ )
    {
        n = 10*n+string[i]-'0';
        p *= 10;
    }
    return s * n / p;
}

void itoa( char* string, int n)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    int i,s;
    if ((s=n)<0)
        n = -n;
    i=0;
    do
    {
        string[i++]= n % 10 + '0';
    } while ((n /= 10)>0);
    if (s<0)
        string[i++]='-';
    string[i]='\0';
    reverse(string);
}

Código: Seleccionar todo

void itoa( char* string, int n)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    string=(char *)malloc(strlen(string));
    int i,s;
    if ((s=n)<0)
        n = -n;
    i=0;
    do
    {
        string[i++]= n % 10 + '0';
    } while ((n /= 10)>0);
    if (s<0)
        string[i++]='-';
    string[i]='\0';
    reverse(string);
}

Código: Seleccionar todo

void itoa( char* string, int n)
{   //  By BlackZeroX ( http://Infrangelux.sytes.net/ )
    string=(char *)malloc(strlen(string));
    memcpy(string,string,strlen(string));
....

Código: Seleccionar todo

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

int main ()
{
  int i;
  int r;
  char buffer [33];
  printf ("Enter a number: ");
  scanf ("%d",&i);
  r=(int)itoa (i,buffer,10);
  printf ("decimal: %s \t %d \t %d ",buffer,(int)&buffer,r);
  fflush(stdin);
  getchar();
  return 0;
}