Now that's changing the more years that pass the more of you have 64-bit computers and the more servers have many, many gigabytes of RAM and so you need actually 64-bits, but for now let's assume a common system whereby a pointer just by definition of the homework is 32 bits.

现在计算机也在改变，也有更多的人,使用64位的计算机，更多的服务器有很多，很多G的内存，那样你就需要64位的，现在我们假设通常的系统中,根据家庭作业所定义的，一个指针为32位。

哈佛公开课 - 计算机科学课程节选