新手求助，帮忙看下一个字符串处理的代码
如果不用strcat函数，把两个字符串连起来。

#include <stdio.h>
#include <string.h>


void main()
{
int m,n;
char a[] = "Hello",b[] = "World";
char c[20];
for (m = n = 0;a[n] != '\0';m++,n++)
c[m] = a[n];
c[m] =' ';
for (n = 0;b[n] != '\0';m++,n++)
c[m] = b[n];
c[m] = '\0';
puts(c);
}

我想在中间加一个空格，怎么加进去？
[解决办法]
for (m = n = 0;a[n] != '\0';m++,n++)
c[m] = a[n];
c[m] =' ';
m++; //加一句
for (n = 0;b[n] != '\0';m++,n++)
c[m] = b[n];
c[m] = '\0';
puts(c);