Siemens Nixdorf PCD-B series, Operating Manual

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The PC System operation
System Unit
The "system unit" comprises:
- the "central processing unit",
- the "main memory",
- the various "controllers"
and
- the "bulk storage" (floppy disk drive or
hard disk drive).
Central processing unit
The central processing unit is the brain of your PC. It executes all your commands.
Main memory
Before, for instance, a text can be processed by the central processing unit, it must be
loaded into main memory. The PC has a main memory of at least 1 Mbyte.
Controllers
The various controllers are responsible for ensuring that the different hardware
components (hard disk drive, floppy disk drive etc.) work properly with the central
processing unit.
Bulk storage
In order to retain texts, spreadsheet data etc. that you have prepared, you must store
them in files in a bulk storage before you switch off your PC. The bulk storage is either a
floppy disk, which has to be inserted into the floppy disk drive when needed, or a hard
disk. The hard disk, in contrast, is built into the PC. When you store files they are
automatically given a date and time so that you can always check when they were
created.
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