Difference Between User Mode and Kernel Mode
User Mode: When a Program is booted up on an Operating system let’s say windows, then it launches the program in user mode. And when a user-mode program requests to run, a process and virtual address space (address space for that process) is created for it by windows. User-mode programs are less privileged than user-mode applications and are not allowed to access the system resources directly. For instance, if an application under user-mode wants to access system resources, it will have to first go through the Operating system kernel by using syscalls.
Kernel Mode: The kernel is the core program on which all the other operating system components rely, it is used to access the hardware components and schedule which processes should run on a computer system and when, and it also manages the application software and hardware interaction. Hence it is the most privileged program, unlike other programs it can directly interact with the hardware. When programs running under user mode need hardware access for example webcam, then first it has to go through the kernel by using a syscall, and to carry out these requests the CPU switches from user mode to kernel mode at the time of execution. After finally completing the execution of the process the CPU again switches back to the user mode.
Difference Between Kernel mode and User mode:
|Kernel-mode vs User mode||In kernel mode, the program has direct and unrestricted access to system resources.||In user mode, the application program executes and starts.|
|Interruptions||In Kernel mode, the whole operating system might go down if an interrupt occurs||In user mode, a single process fails if an interrupt occurs.|
|Modes||Kernel mode is also known as the master mode, privileged mode, or system mode.||User mode is also known as the unprivileged mode, restricted mode, or slave mode.|
|Virtual address space||In kernel mode, all processes share a single virtual address space.||In user mode, all processes get separate virtual address space.|
|Level of privilege||In kernel mode, the applications have more privileges as compared to user mode.||While in user mode the applications have fewer privileges.|
|Restrictions||As kernel mode can access both the user programs as well as the kernel programs there are no restrictions.||While user mode needs to access kernel programs as it cannot directly access them.|
|Mode bit value||The mode bit of kernel-mode is 0.||While; the mode bit of user-mode is 1.|
|Memory References||It is capable of referencing both memory areas.||It can only make references to memory allocated for user mode.|
|System Crash||A system crash in kernel mode is severe and makes things more complicated.||In user mode, a system crash can be recovered by simply resuming the session.|
|Access||Only essential functionality is permitted to operate in this mode.||User programs can access and execute in this mode for a given system.|
|Functionality||The kernel mode can refer to any memory block in the system and can also direct the CPU for the execution of an instruction, making it a very potent and significant mode.||The user mode is a standard and typical viewing mode, which implies that information cannot be executed on its own or reference any memory block; it needs an Application Protocol Interface (API) to achieve these things.|