Computers and Devices
The input–process–output pattern
Every digital device - desktop, laptop, tablet, smartphone, smartwatch - follows the same basic pattern: data enters through input devices (keyboard, mouse, touchscreen, microphone, scanner), the CPU processes it, results leave through output devices (screen, printer, speakers), and anything kept for later goes to storage.
The distinction candidates most often trip on is memory versus storage. RAM is working memory: fast, temporary and wiped when power is lost - which is why unsaved work disappears in a power cut. A hard disk or SSD is non-volatile storage that keeps files when the machine is switched off. A classic exam trap asks where a document sits while you are editing it: it is in RAM, with the last saved copy on disk. ROM holds start-up firmware that must survive power-off.
Software divides into system software (the operating system, drivers, utilities) and application software (word processors, browsers, games). The operating system manages files, memory, devices and the user interface; a driver lets the OS talk to one specific piece of hardware.
Files are identified by a name plus an extension (.docx, .jpg, .pdf, .mp3). The extension signals the file's type, not the program that created it - a .pdf opens in a reader even if it was exported from a word processor. Storage capacity also appears in questions: 1 KB is about a thousand bytes, 1 MB a thousand KB, 1 GB a thousand MB, 1 TB a thousand GB.
Rule of thumb: if you would lose it in a power cut, it was in RAM; if it survives a restart, it is on storage. Save before shutting down.
Keep backups on a separate device or in the cloud, because storage fails and files get deleted by accident.