求教，TCPL一道习题的参考答案有几步看不懂有什么意义。。

在看TCPL，其中有道绘制单词长度分布直方图的习题参考答案给的是

 #include <stdio.h>

#define MAXHIST 15
#define MAXWORD 11
#define IN 1
#define OUT 0

int main()
{
    int c, i, nc, len, state, maxvalue, ovflow, wl[MAXWORD];

    state = OUT;
    nc = 0;
    ovflow = 0;
    for (i = 0; i < MAXWORD; i++)
        wl[i] = 0;
    while ((c = getchar()) != EOF)
    {
        if (c == ' ' || c == '\n' || c == '\t')
        {
            state = OUT;
            if (nc > 0)
                if (nc < MAXWORD)
                    wl[nc]++;
                else
                    ovflow++;
            nc = 0;
        }
        else if (state = OUT)
        {   state = IN;
            nc = 1;
        }
        else
            nc++;
    }

    maxvalue = 0;
    for (i = 1; i < MAXHIST; i++)
        if (wl[i] > maxvalue)
            maxvalue = wl[i];

    for (i = 1; i < MAXWORD; i++)
    {
        printf("%5d - %5d : ", i, wl[i]);
        if (wl[i] > 0)
        {
            if ((len = wl[i] * MAXWORD / maxvalue) <= 0)
                len = 1;
        }
        else
            len = 0;
        while (len > 0)
        {
            putchar('*');
            len--;
        }
    putchar('\n');
    }
    if (ovflow > 0)
        printf("There are %d words >= %d\n", ovflow, MAXWORD);

    return 0;
}

这里有一段

 if (wl[i] > 0)
        {
            if ((len = wl[i] * MAXWORD / maxvalue) <= 0)
                len = 1;
        }
        else
            len = 0;

没看懂啥意思，既然wl[i] > 0, MAXWORD = 15, maxvalve也大于0，那len怎么会<= 0 呢？
我用下面这句替换掉它，测试了一下结果好像是一样的

 len = wl[i] * MAXWORD / maxvalue

所以答案里那一串是干什么用的啊？

求教啊，有人知道吗？