Cambridge O Level Computer Science · Syllabus 2210 · Hardware
Output Device
What is Output Device?
Hardware used by a computer to communicate information to a user or to cause a physical action, converting processed data into a form outside the computer such as an image on a screen, a printed page, sound, a solid object or movement.
This definition is part of the Hardware chapter in Cambridge O Level Computer Science.
Output Device in context
Topic 3 is one machine seen from four distances. Up close, the CPU repeats a single loop — fetch an instruction, decode it, execute it — using named registers and three buses. Step back and the CPU is only useful because input devices and sensors turn physical things into data and output devices and actuators turn data back into physical things. Step back again and nothing survives a power cut unless storage holds it: RAM while the machine runs, secondary or cloud storage afterwards. Step back once more and the machine needs network hardware — a NIC with a MAC address, an IP address and a router — before it can be found and reached by anything else.
Common mistakes with Output Device
- 1. “The CPU is the entire computer.” Why wrong A CPU on its own cannot receive a key press, keep a file after a power cut, or show a result. It is one component among several. Correct model The CPU processes instructions and data and controls the computer's operations. The computer is the whole system: CPU, memory, input devices, output devices and secondary storage. Exam-safe “The CPU processes the instructions and data input into the computer so that a result can be output, and controls the computer's operations.” Check: name three things a computer needs that are not the CPU.Any three of: memory (RAM and ROM), input devices, output devices, secondary storage, buses.
- 15. “A touch screen is only an output device.” Why wrong It counts the display and ignores the touch sensing, which is how data and control signals get in. Correct model A touch screen is both. The display communicates information, which is output; the touch sensing enters data and control signals, which is input. Exam-safe “A touch screen is both an input and an output device: it displays information and it accepts input when it is touched.” Check: name the three touch-screen technologies on the syllabus.Resistive, capacitive and infra-red.
- 16. “A sensor makes the final control decision.” Why wrong A sensor has no stored target value and nothing to compare against. It cannot know whether a reading is acceptable. Correct model A sensor measures a physical property and produces data. A microprocessor compares that data with a stored value and decides. If a condition is met, a signal is sent to an actuator or another output device. Exam-safe “The sensor sends readings to the microprocessor, which compares them with a stored value and, if necessary, sends a signal to an actuator.” Check: fill the gaps — sensor → ______ → ______.sensor → microprocessor (compares with a stored value) → actuator (or another output device).
- 17. “An actuator is an input device.” Why wrong It has the direction backwards. An actuator receives a signal; it does not produce data for the computer. Correct model An actuator is an output device that converts a control signal from the computer into a physical action — movement, opening or closing, switching on or off. Exam-safe “An actuator is an output device that converts a signal from the microprocessor into a physical action.” Check: in a greenhouse system, which is the sensor and which is the actuator — the device that measures the temperature, or the motor that opens the vent?The device that measures the temperature is the sensor (input); the motor that opens the vent is the actuator (output).