Overview of Computers
Overview of Computers
This domain tests the stored-program model, functional units, generations, classification and software types. A computer accepts data, processes it under a stored program, and produces information. The five functional units are input, memory, arithmetic logic unit (ALU), control unit (CU) and output; ALU and CU together form the CPU. The CU fetches and decodes instructions, the ALU performs arithmetic and logical operations, and registers hold temporary data. The machine cycle is fetch-decode-execute-store.
Core rules
- First generation used vacuum tubes and machine language; second used transistors; third integrated circuits; fourth microprocessors; fifth focuses on ULSI, AI and parallel processing.
- Computers are classified by size and purpose: micro, mini, mainframe, super; analog, digital, hybrid; general-purpose and special-purpose.
- Software is system software (OS, language translators, utilities) or application software.
- A translator converts source code: assembler for assembly, compiler for a high-level language as a whole, interpreter line by line.
Worked example
A smartphone is digital, general-purpose and a microcomputer. Its touchscreen is input and its display is output; the SoC contains CPU, GPU and memory; RAM is volatile working memory and flash is non-volatile secondary storage. Calling it a mainframe is wrong because size and role differ.
Traps
ROM is non-volatile; RAM is volatile. The CU does not do arithmetic. A compiler does not execute line by line. Fifth generation is not simply laptops.