Monolithic system
The operating system is written as a collection of procedures, linked together into a single large executable binary program.
How does the monolithic system invoke the OS structure
A main program that invokes the requested service procedure.
A set of service procedures that carry out the system calls.
A set of utility procedures that help the service procedures.
Layered systems layers
0 – dealt with allocation of the processor
1 – memory management
2- process communication
3- I/O management
4- User programs
5- System Operator
Microkernels
- implementation of layered system approach with certain kernel user boundaries
- minimum amount of software required to provide mechanisms to implement an OS.
Hybrid Kernel
runs some services in the kernel space
to reduce the performance overhead of a traditional microkernel,
while still running kernel code as servers in the user space.
Why is it important for an operating system to have kernel mode and user mode?
- Kernel mode allows access to all machine instructions and I/O devices.
- In user mode many sensitive instructions are prohibited.
- The two modes allow the OS to encapsulate user programs.
Threads
- A thread is essentially a piece of instruction which is managed by the operating system.
- They perform activities around the process rather than running the process itself
Starting up chrome
- Ram holds program code and data
- Instruction bytes are copied from storage to RAM
- CPU is directed to start running at the first instruction
- Chrome is launched
Virtual Machine Uses
Game emulators Dual Booting Disaster Recovery cloud tech Containers
BIOS proper def
- The BIOS contains low-level I/O instructions,
- Loads os onto main memory then stores config info for peripherals (keyboard etc.)
- performs system integrity checks
Race conditions
When it comes to processes and threads a race condition can cause bugs.
This occurs when a process or a thread depend on some shared state and they are not mutually exclusive.
Mutual Exclusion
Mutual exclusion is the requirement that one thread of execution never enters a critical section while another thread happening at the same time of execution is already using the critical section.
Stack
- Stack is a stack of information/nodes stacked one over another with the highest address node placed at top
- When an information is added, memory is incremented by 1 and when an information is removed, memory is reduced by 1.
- Follows last in first out(like a stack of plates)
2 major functions of stack
a) Push - Adding information to the stack
b) Pop - Removing information from the stack
GRUB proper def
- GRUB needs to understand the file systems,
- the kernels executing commands
- works like a transfer step on passing control to the operating systems kernel software from the MBR.
