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Communication requires agreement about symbols, timing and meaning. Keep signalling rate, useful data rate and delay separate when comparing links.
What you'll be able to do
Serial transmission sends successive bits along a communication channel; parallel transmission sends several bits at the same time over separate lines. Parallel can transfer multiple bits per timing event, but more conductors, interference and arrival-time skew complicate longer links. Serial designs can support high rates with simpler cabling.
Neither label alone determines which real device is faster. Synchronous transfer uses an agreed timing relationship, while asynchronous character transfer can use start and stop bits to frame each unit and let the receiver synchronise its reading. The exact framing format must be stated.
Baud rate counts transmitted symbols per second. If each symbol represents k bits, the raw bit rate is baud×k. For M equally available signal symbols, a fixed code can carry log₂M bits per symbol when M is a suitable power of two. Baud is not merely the number of visible changes in a run of identical symbols.
Bandwidth describes available frequency range in a physical channel, while networking also uses the word for data capacity. Greater available bandwidth can support a greater bit rate under suitable coding and noise conditions; it is not a universal conversion from hertz to bits per second without assumptions.
Start, stop, parity and protocol information consume transfer capacity without all being application payload. For eight data bits plus one start and one stop bit, ten transmitted bits carry one eight-bit character. Useful throughput is lower than the raw bit rate.
Latency is delay from the relevant start event to arrival or response, depending on the measurement definition. A high-capacity link can still have substantial latency. A protocol specifies rules such as format, ordering and responses so that the receiving system can interpret the transferred data.
| Quantity | Meaning |
|---|---|
| Baud | Symbols per second |
| Bit rate | Bits per second |
| Payload throughput | Useful data per second |
| Latency | Delay under the stated measurement |
Attempt the task before opening its worked response. Record each change of state, explain the rule used, and check the result against the original requirements. Code examples labelled Python 3 use that language’s conventions; pseudocode states its own assumptions.
Common mistakes to avoid
Key takeaways
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.