The OS takes care of booting up, login and user management, window management, memory allocation, storage interfaces, background services, peripheral management, and much more. Access to these services, where allowed, is provided in the form of software libraries that developers can use.
A hard disk is organised into sectors, which are the smallest unit of storage. The OS’s filesystem determines how and where to store each file on the hard disk. The filesystem manages the file metadata in a file table, separate from the actual contents of the file.
When write operations are interrupted prematurely, filesystem corruption often results.
Safe writes ensure that all the data is written to disk sectors properly first before updating the file table. The result is that write operations take a longer time to complete.
Fast writes dump the data to a write cache (in computer memory), then update the file table to look like the file is already written to disk. However, if power is cut before all data is properly moved from the write cache to disk, the data in memory is lost, and file corruption usually results.
Filesystem journals are a record of changes made to the disk, so as to enable those changes to be rolled back, or to be completed properly in case of sudden interruption.
Moving a file (within the same disk region) merely updates its file table record, and this happens really quickly. Copying a file, or moving it to a different disk/region, involves copying the contents and then updating the file table record, and is considerably slower. Deleting a file only requires that its file table record be removed, and is a very fast operation (if it does not involve the Recycle Bin).
When a computer is booted up, it runs the BIOS from a chip on the motherboard. The chip checks that core parts are present, checks for a storage disk containing a bootloader, loads it into memory, and hands over control. The bootloader loads the operating system kernel. The operating system kernel then does whatever it needs to do to get the system ready for use.
f you can’t get to a BIOS screen, it is likely a hardware problem and has to be solved by a technician. If you can’t get the OS loading screen, it’s a bootloader problem and needs to be solved with more geekery. If something goes wrong with OS loading, and fails to fix itself on subsequent reboots, it’s probably time for a system refresh or reinstall.
Embedded operating systems are unlike user operating systems. They are designed to run the software needed for an appliance’s operation, and are not meant to be used by users directly. Since they are considered somewhere between software and hardware, they are usually referred to as firmware.
When you shut a computer down, it sends an exit signal to all running programs to get them to do their exit routine. This process can sometimes take a long time. To preserve the data configuration in memory while minimising power draw, a computer can go into standby mode: all hardware except the memory gets powered down, until the computer is woken up from standby.
Hibernation mode causes the computer to store the data configuration into a hibernation file on disk. When powered up, the OS reads the data configuration from the file back into memory. This lets the system avoid having to do a full shutdown and bootup; it performs a shorter version of these two sequences instead.
Operating systems use a page file on the storage disk as a complement to physical memory. This allows OSes to behave more performantly than they would if they did not have a page file. Data that is rarely accessed is moved to the pagefile (“paged out”), and can be paged in when it is needed later, albeit with a performance hit.