Csit 431 Ch 2 Quiz #1

the interface between the hardware and software

User Mode

Kernel Mode

Programs use this mode, it is a protected mode so user programs cannot damage resources or make them unusable

The mode the OS uses to interact with the processor

- User no longer has direct access to processor

- Controls the sequence of events

- Resident monitor is software always in memory

- Reads in job and gives control

- Job returns control to monitor

The number of programs that can be resident in main memory at the same time.

- in modern systems, if memory is full, it swaps data to hard disk that is waiting for something that is ready to run.

Processor intensive

Sequential operation, one after the other

- Earliest systems

-Main focus was to accept jobs from user, schedule them and then execute them

- Main goal was to improve throughput

- Maximize # of jobs completed

-Totally automated, gets job from file, returns to file

- User interaction, not automated

- Main goal was response time (the avg time it takes to get a response for a command)

Memory protection

- stop access to kernel or another users memory

The kernel turns to user mode before turning control over to users program to run, when control is handed back it goes back into kernel mode.

A program in execution

It must be brought into main memory, when it is executed it becomes a process.

1. An executable program(code)

2. Associated data(variables and constant's)

3. Execution context (values in the registers when program is interrupted)

When the output is different depending on the order of the programs running.

- A program should not should not depend upon another, should be the same no matter the order in which they are executed.

A program 1 is waiting on program 2 at the same time program 2 is waiting on program 1.

Making sure 2 programs do not try to modify a shared resource at the same time.

- Non shareable resources must be assigned to one process only.

blocking a program until a particular event occurs

-Programs loading is on demand(only when needed)

- It generates a logical address (page # followed by offset)

When a program requests a page, it loads it

-keeps a table of pages(page table for each program)

Decides which job to run next

- OS uses queue's to do this

- A very small kernel

- Only essential function in the kernel mode

- Rest are kept in user mode

- Much easier to test

- bundles everything into one program

- More difficult to test

- Very large , 10's of thousands lines of code

thread is a very light weight process, threads can be part of a process, and a process can have many threads that share the data of the process.

processes that are ready to run

Processes waiting for I/O data requested to arrive

used when multiple processes are requesting the services of a I/O device, this is handled by the OS

- non paging

- One big piece of code

- cannot be interrupted

- simplifies implementation

- divided into threads that can run concurrently

- dispensable unit of work

- includes a processor context and its own data are to enable subroutine branching

-executes sequentially and is interruptible

- term refers to computer hardware architecture

- several processes can run in parallel

- all processors can perform the same functions

- processors share same main memory and I/O facilities

-Performance, more than one process can be run at the same time

- Availability, Failure of a single processor does not halt the system

- Incremental growth, can add more processors to improve performance

- Scale-ability, allows room for growth of system without needing to redesign

- A single main memory space

- Single secondary memory space

- unified access to facilities

- Used for adding modular extensions to a small kernel

- Enables programmers to customize a OS without disrupting system integrity

-Eases development of distributed tools and OS systems

The ability of a system of component to continue normal operation despite the presence of hardware or software faults

- typically involves some degree of redundancy

the probability of correct operation up to a time given the system was operating correctly

Average time that the system runs without failures

the average time it takes to repair the system and bring it back online

defined as the fraction of time the system is available to service users requests

Managing resources

- efficiency

- fairness

- differential responsiveness

- Reliability

- Mean time to failure MTTF

- Mean time to repair MTTR

- Availability

Permanent (after occurs it is always present)

Temporary (not always present)

Transient (only happens once)

Intermittent (happens multiple times and is unpredictable)

- process isolation

- concurrency

-virtual machines

checkpoints and rollbacks

The processor is not waiting on the slower I/O devices. It can move on to next process and goes back using the interrupt when the process is ready.

Holds the address of the current instruction being executed.

1. MAR sends instruction to memory

2. memory returns address to MBR/MDR

3. MBR/MDR sends address to the IR

The principle of what the SRAM will store.

1. Data the CPU may need again

2. Adjacent data to CPU may need

To prevent and protect users memory area from other users.

I/O devices are much slower than the processor, so using interrupts allows the processor to do other tasks without having to wait on slower devices.

-size of cache

-size of the block to retrieve

-mapping scheme

- process isolation, automatic allocation and management to support modular programming

- It stores address in a table so it can use virtual memory and find data quickly

It retrieves the block from the disk that contains what is needed and adds entry into the table in allowing for dynamic mapping between virtual address using in programs and address in main memory