Computer Hardware
FoundationComputer hardware consists of the processor, main memory, secondary storage and input/output devices: the processor computes and controls, main memory holds running programs, storage keeps data long term. Knowing each part's role and speed reveals where performance bottlenecks lie.
- The processor contains the arithmetic and logic unit, control unit and registers, repeating the fetch-decode-execute cycle
- RAM loses its contents on power loss; ROM keeps the boot-up firmware
- Hard disks: large, cheap, slow; solid-state drives use flash memory — fast and shock-resistant
文體小知識：科技知識說明文——介紹中央處理器、主記憶體、輔助儲存器和輸入輸出設備的分工，說明數據流向與性能瓶頸。
§Text Passage
1The central processing unit is the computer's computing core: the arithmetic and logic unit performs calculations and comparisons; the control unit directs the parts to work in step; registers are fast storage inside the processor holding the instructions and data being processed. The processor repeats the fetch-decode-execute cycle — fetching an instruction from main memory, decoding it and executing it — endlessly, with speed measured by clock rate.
2Main memory comes in two kinds: random access memory is readable and writable but loses its contents when power is cut, and running programs must first be loaded into it; read-only memory holds start-up firmware written at the factory and survives power loss, handling boot-up. Between them sits cache memory — small but extremely fast, keeping frequently used data to reduce waiting. When memory runs short, overall performance drops noticeably.
3Secondary storage keeps the operating system, programs and files long term. Hard disks read and write with spinning platters and mechanical arms: large capacity and low cost per unit, but speed is limited by mechanical movement. Solid-state drives use flash memory with no moving parts — much faster to read and write, shock-resistant and durable, but dearer per unit. Secondary storage retains data without power and usually far exceeds main memory in size.
4Input devices bring data into the computer — keyboard, mouse, scanner; output devices present the results — monitor, printer, speaker; the parts are connected by buses carrying data. The data flow runs: input devices enter the data, the processor computes with main memory, and the results are held in memory, written to secondary storage or shown through output devices — five departments, each doing its own job.
1Summary 重點摘要
Computer hardware consists of the processor, main memory, secondary storage and input/output devices: the processor computes and controls, main memory holds running programs, storage keeps data long term. Knowing each part's role and speed reveals where performance bottlenecks lie.
2Vocabulary cards Vocabulary
The physical components of a computer system, such as the processor, memory and storage devices.
The chip that executes instructions, containing the arithmetic and logic unit and the control unit.
The part of the processor that performs arithmetic and logical comparisons.
High-speed storage inside the processor holding the instructions and data being worked on.
Readable and writable main memory that programs must be loaded into; contents are lost when power is off.
Memory holding boot-up firmware written at the factory; contents survive power loss.
The processor's repeating sequence of fetching an instruction, decoding it and executing it.
Small, very fast memory between the processor and main memory holding frequently used data.
Long-term storage such as hard disks and solid-state drives that keeps data without power.
Non-volatile memory used in solid-state drives and USB storage.
3Step by step Steps
- Step 1: Five departments of hardwareA computer splits into five functional departments: input devices receive data, the processor computes and controls, main memory holds running programs and data, secondary storage keeps data long term, and output devices present results — all connected by buses. For example, typing a sentence: the processor computes instantly, characters appear on screen, and saving writes to the disk. Five departments, each indispensable.
- Step 2: Inside the processorInside the processor, the arithmetic and logic unit calculates and compares, the control unit decodes instructions and directs the parts, registers hold the current instructions and data at top speed, and cache keeps frequently used data to cut waiting. For example, computing 25 × 4: the instruction and values enter the registers, the arithmetic and logic unit produces 100, and the result returns to a register — all inside the processor.
- Step 3: The fetch-decode-execute cycleThe processor loops through three steps endlessly: fetch the next instruction from main memory, decode what it means in the control unit, execute it with the parts, then fetch again. For example, while music plays, the processor executes hundreds of millions of instructions per second to send sound data to the speaker; the higher the clock rate, the more cycles per second and generally the faster the processing.
- Step 4: Two kinds of main memoryRandom access memory is readable and writable — the stage on which programs run — but vanishes when power is cut; read-only memory carries boot-up firmware from the factory and survives power loss, handling start-up. For example, an unsaved document disappears with the RAM in a blackout; on reboot, the firmware in ROM runs first so the computer can start. Hence the habit of saving important files at once.
- Step 5: Comparing secondary storageHard disks read and write with platters and mechanical arms: large capacity and low price, but mechanical movement is slow and shock-sensitive. Solid-state drives store data in flash memory with no moving parts — several times faster at booting and loading, shock-resistant, but dearer per unit. For example, swapping a hard disk for a solid-state drive cuts boot time from over a minute to seconds — one of the best-value upgrades.
- Step 6: Input and output devicesInput devices turn real-world data into digital signals — keyboard, mouse, scanner, microphone; output devices turn results back into human-perceivable form — monitor, printer, speaker. For example, in a video call the camera and microphone are inputs, the screen and speakers are outputs, and data flows back and forth between the two kinds of device through the processor and buses.
- Step 7: Performance bottlenecksOverall speed is decided by the slowest critical part — the bottleneck. A weak processor stutters on computation; insufficient memory forces the system to lean on secondary storage and everything slows; a hard-disk-only machine loads files slowly. For example, a video-editing PC with ample memory but only a hard disk saturates the disk when exporting footage while other parts idle — upgrading to a solid-state drive helps most.
4Diagrams Diagrams
5Worked example Example
A student has a budget of $6000 to build a computer, mainly for word processing and online learning with occasional video editing. Two quotes: Plan A has a faster processor, 8 GB RAM and a 1 TB hard disk; Plan B has a slower processor, 16 GB RAM and a 256 GB solid-state drive. Analyse both and recommend a choice.
- Plan A analysis: the faster processor helps export footage, but 8 GB RAM is near its ceiling with a browser, office software and an editor open at once; the 1 TB disk is roomy but slow, making loading footage tedious.
- Plan B analysis: 16 GB RAM runs several programs comfortably, and the solid-state drive markedly speeds up booting and loading footage; the slower processor takes longer to export clips, acceptable for occasional editing.
- Bottleneck judgement: Plan A's bottlenecks are memory and disk, slowing every step of daily use; Plan B's bottleneck only appears in occasional exports, leaving daily use smooth.
- Recommendation: for daily use choose Plan B; upgrade the processor later when budget allows, and add an external disk for capacity.
- Answer: Plan A has the faster processor but 8 GB RAM is close to the multitasking ceiling and the 1 TB hard disk slows every file read and write — bottlenecks in memory and storage. Plan B doubles the memory and gains a solid-state drive, making daily work, study and light editing smooth; its only weakness is slower occasional exports. For word-processing-and-study use with rare editing, everyday experience matters more than occasional computation: choose Plan B and upgrade the processor later. The key is identifying each plan's bottleneck and weighing it against actual use.
6Common mistakes Mistakes
7Quick check Quick check
Q1Which part inside the processor performs arithmetic and comparisons?
Q2State the three steps of the fetch-decode-execute cycle.
Q3What happens to RAM and ROM when the power is cut?
Q4What are the advantages and disadvantages of a solid-state drive compared with a hard disk?
Q5A computer boots and loads programs slowly. Which component is most worth upgrading first?
8Recap Recap
- The processor contains the arithmetic and logic unit, control unit and registers, repeating the fetch-decode-execute cycle
- RAM loses its contents on power loss; ROM keeps the boot-up firmware
- Hard disks: large, cheap, slow; solid-state drives use flash memory — fast and shock-resistant
- Input devices bring data in, output devices present results, buses connect the parts
- Overall performance is set by the slowest bottleneck — upgrade where it hurts