Arithmetic/logic (演算) is the function that performs calculations such as addition and comparisons of size on data.
Computation is carried out by the arithmetic logic unit inside the CPU, which together with the control unit makes up the CPU (processor). It includes arithmetic operations, which calculate with numbers, and logical operations, which combine true/false values with AND, OR and similar operators.
AnalogyThink of a clerk who quickly and accurately finishes whatever sums are handed over. What to calculate always comes from someone else.
How to rememberThe kanji 演 means "to perform", as on a stage: picture an actor who goes on only after receiving the script, which here is the instruction.
Exam points
ExamArithmetic/logic (演算) is the side that carries out calculations and comparisons as directed by control (制御).
Control (制御) is the function that takes program instructions out of storage, decodes them, and directs the other units to act.
Fetch
Decode
Execute
Next instruction
Go back to the start and repeat the same flow with the next instruction.
4 / 4
Control is the job of the control unit inside the CPU. The control unit keeps the location in main memory of the next instruction to process (its address) in a storage location called the program counter, and moves that value on to the next instruction each time it fetches one. Repeating fetch, decode and execute in this way moves the program forward step by step.
AnalogyIt is like a conductor who reads the score bar by bar and cues each player to come in, without playing an instrument himself.
How to rememberThe kanji 制 carries the sense of regulating and keeping things in order, a reminder that this function runs the whole show.
Exam points
ExamThe program counter (プログラムカウンタ) is a storage (記憶) location inside the CPU that points to where in main memory (主記憶) the next instruction to process is held, that is, its address (アドレス).
Storage (記憶) is the function that holds programs and data so they can be read or written when needed.
Storage location
Where it sits
Speed
Capacity
Registers
Inside the CPU
Fastest
Very small
Main memory
Outside the CPU (memory)
Fast
Medium
Auxiliary storage (e.g. SSD, hard disk)
Connected as a device
Slow
Large
A computer places the program it will run in storage beforehand and then fetches its instructions one after another (the stored-program concept). The units that provide storage are main memory, which the CPU reads and writes directly, and auxiliary storage, which keeps programs and data for the long term, while the CPU itself also contains tiny storage locations called registers.
AnalogyIt resembles the difference between a note in your hand, papers spread on your desk, and files stored away in an archive. The closer something is, the faster you can use it, but the less of it fits.
Exam points
ExamA register (レジスタ) is a storage location inside the CPU that can be read and written far faster than main memory (主記憶), but it holds only a tiny amount.
Mix-upMain memory (主記憶) holds the programs and data currently running, and its contents are lost when the power goes off. Auxiliary storage (補助記憶) keeps its contents without power and serves as long-term storage.
Input (入力) is the function that brings data and instructions from people or external devices into the computer.
Input is handled by input devices such as keyboards, mice and scanners. The data they bring in travels to main memory and other units over the shared pathway that links the units (the bus).
AnalogyIt is like a shop's front desk, which takes a customer's order and passes it to the workshop in the back.
Exam points
ExamA bus (バス) is a shared pathway that links the CPU with main memory (主記憶) and input/output devices (入出力装置) so the units can exchange data.
Output (出力) is the function that sends the results of processing inside the computer out in a form people or external devices can use.
Output is handled by output devices, for example a display that shows things on screen, a printer that puts them on paper, or a speaker that produces sound. What they send out is data held in storage, such as the results of computation.
AnalogyIt is like the pickup counter that hands finished goods from the workshop to the customer.
Exam points
Mix-upInput (入力) and output (出力) are distinguished by direction: whether data comes in from outside or goes out from inside. Some devices, such as a touch panel (タッチパネル), handle both.
A computer has five functions: arithmetic/logic, control, storage, input and output.
The CPU (processor) consists of the arithmetic logic unit and the control unit.
The control unit tracks the location of the next instruction with the program counter and moves the program forward by repeating fetch, decode and execute.
Storage locations include the registers inside the CPU, main memory and auxiliary storage; the closer to the CPU, the faster but the smaller.