IIRC, sentience could be achieved building a purpose driven program sophisticated enough to recognize productive algorithmic content and expand it's programming. Programs in the range of a few hundred terrabytes should be sophisticated enough to "learn". Providing a storage capacity of a few hundred exobytes could allow a program to at least gain self awareness. Sentience would be less likely. But the chance is significant enough.

Ones and zeros can be random, or they can have purpose. Humans perceive purpose. If machines perceive purpose, it will be interesting to see how they respond. The missles in the silos may be operated by antiquated computing systems, but humans control those systems. Who controls the humans, and how?