C语言程序设计 习题问题 求高手帮忙下

[snakes13]

看书看到 int atoi(char s[]) 函数的时候 不太理解 想运行看看到底什麽意思

然后自己加了个主函数 想运行 通不过编译 求高手帮忙下 应该怎么修改下

谢谢大家先

代码如下

#include <stdio.h>
#include <ctype.h>

int atoi(char s[]);

main()
{
  int c, i ;
  
  for (i = 0; (c = getchar()) != EOF ; ++i)
    s[i] = c;
  printf("%d", atoi(s[i]));
}

int atoi(char s[])
{
  int i, n, sign;
  
  for (i = 0; isspace(s[i]); i++)
    ;
  sign = (s[i] == '-') ? -1 : 1;
  if(s[i] == '+' || s[i] == '-')
    ++i;
  for(n = 0; isdigit(s[i]); i++)
    n = 10 * n + (s[i] - '0');
  return sign * n;
}

[wzywsk]

#include <stdio.h>
#include <ctype.h>
#define MAX 20
int atoi(char s[]);

main()
{
  int c, i ;
  char s[MAX];
  for (i = 0; (c = getchar()) != EOF ; ++i)
    s[i] = c;
  printf("%d", atoi(s));
}

int atoi(char s[])
{
  int i, n, sign;
  
  for (i = 0; isspace(s[i]); i++)
    
  sign = (s[i] == '-') ? -1 : 1;
  if(s[i] == '+' || s[i] == '-')
    ++i;
  for(n = 0; isdigit(s[i]); i++)
    n = 10 * n + (s[i] - '0');
  return sign * n;
}

[太乙]

/* atoi example */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  int i;
  char szInput [256];
  printf ("Enter a number: ");
  fgets ( szInput, 256, stdin );
  i = atoi (szInput);
  printf ("The value entered is %d. The double is %d.\n",i,i*2);
  return 0;
}