CISC 361 terms/definitions

Monolithic kernel

Kernel performs all major functions of the OS; Traditional UNIX

Microkernel

Very small kernel provides only the most basic services to support processes

and threads; Servers

Operating system

Only program that runs directly on the hardware and can access the

hardware directly

Process

Program in execution

Process Control Block (PCB)

data structure used by an operating system to store all the essential information needed to track, manage, and control a specific process

Process Control Block contains

– Process ID

– Process state

– Parent

– Files open

– CWD

– Context (CPU Registers, etc.)

– Virtual memory table

Limited Direct Execution

prevents user programs from taking control or interfering

with other user processes or the O.S. itself

Traps

Allow user programs to ask the O.S. to execute operations that the User program is restricted from executing, allowing the program to access services and the O.S. to maintain control over how they are accomplished.

Interrupts

Mechanism for the O.S. to rest control from User processes when hardware events occur

Multiprogrammed system

A system that can run more than one program at a time

Batch system

OS system where a process runs until it is completed

Quantum

Amount of time that any process is allowed to stay on the cpu

Context Switch

The process of taking processes on and off the CPU based on the quantum ; involves backing up the state of one process to it’s PCB, and restoring the state of the new process from the PCB

Turnaround Time (TAT)

The time it takes from when a program is first created until it is complete (Tturnaround = Tcompletion - Tarrival)

Response Time

The time it takes from when a program arrives until it gets its first opportunity to run on the CPU (Repsonse time = First run time - Arrival Time)

Throughput

Number of jobs completed per unit time (Throughput = #jobs/time)

Fairness

CPU time or system resources are divided equitably among users, processes, or threads

Starvation

Resource Management issue where a low-priority process is delayed indefinitely because higher-priority tasks continuously monopolize the CPU

fork()

system call that creates a new process