Usually, operating system software is loaded into RAM automatically when a computer is powered on. This is termed 'the bootup process', as in the adage 'pick yourself up by your bootstraps'. We're used to waiting for bootup process to complete before we can log into whatever device we just booted up. It can take several seconds with a SSD-Solid State Drives or lots longer with HDD-Hard Disk Drives. If there are lots of apps in the Task Manager's Startup tab it can take minutes for our computer to settle down so we can use it. Often it leads us to 'decrapify' the platform we just purchased to speed up the boot process...
Bootup is ubiquitous in all our modern machines. Servers, mid-range, mainframe, and even teeny-tiny computers embedded in Routers, household appliances, TVs, watches, or DVD Players all 'boot up' when the power's turned on.
After the computer's booted and there are no errors, it's ready to run our applications.
Prior generation computers' bootup processes were manual, with no bootstrap loader. The computer operator flipped switches to set the address of the magnetic or paper tape drive, card reader, or disk holding the 'boot image' necessary to run the application at hand. Then, we'd press the Run button and see FLAB - Flashing Lights Acting Busy until the beast finished the boot process and the console sprang to life...
The BIOS-Basic Input/Output Systemis usually located on a ROM-Read Only Memory mounted on the mainboard or built into a SoC - System on a Chip. Where old ROMS were truly 'read only' and couldn't be updated, most today are 'flashable' so the BIOS can be updated when needed.
When the computer is switched on it's circuitry runs the BIOS which launches a POST-Power On Self Test to make sure the hardware's capable of booting. If the POST runs cleanly the BIOS continues with loading the operating system.
After the POST, the process continues to seek the bootable device configured into the BIOS, which may be a hard disk or solid state drive, usb, sd card, or network interface. When the OS on the bootable device has been loaded our computer's ready to run applications, usually starting with those in the Startup Tab or Folder.
Booting into Safe Mode provides a way to avoid startup applications or advanced features that may interfere with a normal boot. It allows us to run startup apps one at a time to help diagnose problems, reconfigure the startup processes, or remove problem software.
UEFI-Unified Extensible Firmware Interface has replaced the traditional BIOS on most new computers. When Macs switched to Intel, Apple put EFI on their machines. Then 'the industry' got together and decided on UEFI as industry standard. Released in about 2007 but slow to be widely adopted, by 2017 we find it on most computers.
But, lots of us still refer to it as 'BIOS'.
UEFI allows for more options at bootup, bootup from larger disk drives, 64-bit processing, better security and malware avoidance, and remote access to the UEFI firmware where the old BIOS requires being physically at the machine as it boots. Some manufacturers take advantage of UEFI enhanced graphics capability to make a full GUI that supports the mouse, while others leave it at the old CUI-Charracter User Interface.
Some computers still have the old BIOS available for backward compatibility with some hardware and features, but reasons to use it are rare.
Network managers and techs, or PC owners, need get directly to the BIOS to make changes in hardware configuration or security settings. Most PC/Server BIOSs are accessed by tapping some key during the bootup. The F12 and F2 keys are common, but aren't the only keys used for accessing the BIOS. Most computers momentarily flash their BIOS access key on the monitor or command line early in the bootup sequence. Googling something like 'how to enter bios on my dell xps' often gets a useable response.
An example of this would be changing the bootup device, so that a computer is booted from the USB or DVD instead of its HDD-Hard Disk Drive or SSD-Solid State Drive.
Please, enter the BIOS on a couple of the notebook and desktop computers at your fingertips and consider what's there.
The BIOS provides a simple menu to check and change settings. If changes are made they are flashed into the BIOS ROM and used whenever the machine is rebooted.
This ability to alter the bootup process must be secured and managed carefully! Otherwise, some crook can load their own rogue OS and pillage the machine. An employee who can reboot a machine and enter the BIOS has a whole 'nother, very rich, vector to attack the employer's networks, servers, and co-workers machines.
Old BIOS usually allowed a jumper or switch to be set on the mainboard to disable changes to the BIOS. But, a knowledgeable cracker can take the cover off and have their way with the machine. Booting with a live Linux distro, for example, defeats portions of Windows or Mac security so whoever boots the machine has access to everything on it!
UEFI provides multiple options for protecting the bootup process.
One may 'dual boot' their system to choose the OS that will boot and run the machine. GPARTED-Gnu Partiion Editor and GRUB-Grand Unified Bootloader are open source tools. BootCamp is a Mac product, and the Windows Disk Management Utility are some other options for 'dual booting' a notebook or desktop computer. Hyper-V, available free with Windoze Server from the MSDNAA is gaining huge market share in Windows environments.
Dual-booting software provides a 'boot menu' that appears whenever the computer is restarted. Several differently configured OS may be on the machine and you pick the one to run after power up. It runs one OS at a time, with the only communication being their shared file system.
Booting from a 'Live Distro' is a good way to see if a machine will run a Linux flavor like Ubuntu or Fedora. A DVD is prepared for the live distro, and the BIOS set to boot from a DVD first instead of the HDD. The new OS will boot and run from the DVD, and may be used to mount the file system on the machine's HDD or SSD. This circumvents any file security that might be provided by Windows, and all un-encrypted data is available to whoever boots the live distro...
A better option, and more salable skill, is to 'virtualize' your machine using a free product like Sun/Oracle's VirtualBox or Microsoft's HyperV for free, or spring $79 for VMWare Workstation -- VMWare still has lots of market share. Virtualizing your computer allows you to run two or more OSs simultaneously, depending on how many cores and gigabytes you've got, and switch between them as easily as switching between browser windows.
If your machine has 8+ Gigs of RAM and Quad-cores or better it is a good target for virtualization. The OS installed on the machine as purchased becomes the 'host OS' and is able to run as many 'guest OS' as will fit in its RAM and share the CPU cores available.
Mac users in the School of Business need to be able to run Windows apps like Visio and Visual Studio so this is a good time to get skills with virtualization, or be stuck working in the 2nd floor lab. Parallels is an easy option but only works with Windows and Mac and doesn't provide VLANs and other features of 'real virtualization software' like VMWare or VirtualBox.
Old Mac OS X with slow processors and new ones like MacBook Air do not virtualize well, and dual-booting with BootCamp might be the best option for them. Recent MacBook Pros with 8+ Gigs and Core technology are fine for virtualizing...
Please, get a nice, quick machine if you don't already have one. The instructor can relate lots of frustrating experiences where an old MacBook running VirtualBox takes _minutes_ to accomplish what a native Windows machine can do in _seconds_.