Computer Systems and Networks: Hardware, the Internet, and Security
What this big idea asks you to know
Big Idea 4 covers how computers and networks operate. Know the roles of the CPU, memory (RAM), storage, and input/output devices, and the idea that programs and data are both stored in memory. Understand the internet as a network of networks using packets, IP addresses, routers, and layered protocols (with HTTP and TCP/IP as examples). Know the difference between the internet (infrastructure) and the World Wide Web (an application on top of it). Understand redundancy and fault tolerance, bandwidth, latency, and the basics of cybersecurity: encryption, authentication, and why phishing and weak passwords are common vulnerabilities.
Concepts to master
- Packet switching: data is split, routed independently, and reassembled.
- Redundancy keeps communication working when a path fails.
- Open standards and protocols allow heterogeneous devices to interoperate.
- Symmetric vs. public-key encryption at a conceptual level.
- The digital divide: unequal access to computing and connectivity.
Traps to watch for
A frequent trap is equating the internet with the web. Another is assuming packets always take the same route or arrive in order. Watch for answers claiming encryption makes data unreadable to the intended recipient - it doesn't; keys allow decryption. Also beware of overstating what a single security measure guarantees.
Rule of thumb
For network questions, separate infrastructure (routers, packets, IP) from application (web pages, email). For security questions, ask who holds the key?
Worked example: If one router fails, packets are re-routed through other paths - this is redundancy providing fault tolerance.