Section 1
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System programs
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Last updated
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Date created
Mar 1, 2020
Cards (167)
Section 1
(50 cards)
System programs
is associated with the operating system but are not necessarily part of the kernel
Direct memory access
allows data to be sent directly from an attached device, such as a disk drive, to the memory on the computer's motherboard
context switch
State save of the current process and state restore of a different process
user mode
non-privileged mode in which each process starts out; forbidden for these processes to access portions of memory that have been allocated to the kernel or to other programs
Swapping
processes are swapped in and out of main memory to the disk
Asymmetric multiprocessing
multiprocessor systems in which each processor is assigned a specific task
Instruction register
the part of a CPUs control unit that holds the instruction currently being executed or decoded
kernel mode
has root privileges, permission o access any memory space
MMU (Memory Management Unit)
a hardware component that handles all memory and caching operations associated with the processor; responsible for all aspects of memory management
NVRAM
nonvolatile RAM; DRAM with battery backup power; nonvolatile as long as the battery lasts
Magnetic disk
provides storage for programs and data using magnetic storage to store and retrieve digital information using one or more rigid and rapidly rotating disks
Interrupt
signals the occurrence of an event that needs immediate attention
Minicomputer
a computer of medium power, more than a microcomputer but less than a mainframe
Volatile
able to change
Solid-state disks
nonvolatile; faster than hard disks
ROM
read-only memory; non-volatile memory
process control block
The data structure used by the operating system to manage information about a process and its state
Mainframe
a large high-speed computer, especially one supporting numerous workstations or peripherals
Symmetric multiprocessing
multiprocessor system in which each processor performs all tasks including operating system functions and user processes.
Multicore
multiple processors on a single chip, which is faster than between chip communication and uses less power
Virtual memory
a technique that allows the execution of a process that is not completely in memory
Hot-standby mode
system only monitors the active server, in case the running server fails, than server in this mode takes over
Middleware
a set of software frameworks that provide additional services to application developers
Nonvolatile storage
does not lose its contents without power
Kernel
the operating system running at all times on the computer
Firmware
permanent software programmed into read-only memory
Bootstrap program
the initial program run when the computer starts which initializes all aspects of the system from CPU registers to device controllers to memory contents; must know how to load the OS and how to start executing that system
Asymmetric clustering
one system is in hot-standby mode while the other is running the application
Workstations
a personal minicomputer connected to networks of other personal computers and servers
Response time
the time taken for a circuit or measuring device, when subjected to a change in input signal, to change its state by a specified fraction of its total response to that change
Physical memory
an actual device holding memory
RAM
random access memory; any byte of memory can be accessed without touching the preceding bytes; retains data bits in its memory as long as power is being supplied (static)
Interrupt driven
if there are no interrupts, an OS will sit quietly waiting for something to happen
Interrupt vector
an array of addresses pointing to interrupt routines; this speeds up the handling of interrupts by providing an address book where the interrupt can quickly and accurately transfer to control to the appropriate interrupt service routine
DRAM
dynamic random access memory; needs to be periodically refreshed or it will lose its contents
Moore's law
predicted the number of transistors on an integrated circuit would double every eighteen months
Servers
manages access to a centralized resource or service in a network
Logical memory
a translation of memory to a physical device
Symmetric clustering
two or more hosts are running applications and are monitoring each other
EEPROM
electrically erasable programmable read-only memory; read-only memory whose contents can be erased and reprogrammed using a pulsed voltage
program counter
a register in a computer processor that contains the address of the instruction being executed at the current time
System processes
another term for system daemons
Device driver
used by device controllers to manage I/O; provides a uniform interface between the kernel and the controller
Von Neumann Architecture
modern computer structure consisting of four subsystems: memory, I/O, arithmetic logic unit, and control unit, and the stored program concept and sequential execution of instructions concept
Multiprocessor systems
Computer systems with two or more processors in close communication, sharing computer bus and sometimes the clock, memory and peripheral devices
Trap (exception)
a software-generated interrupt caused either by an error or by a specific request from a user program that an OS service be performed
System daemons
a computer program that runs as a background process rather than being under the direct control of an interactive user
System call
an operation that software calls to trigger an interrupt
Monitor call
another term for system call
Secondary storage
must be able to hold large quantities of data permanently (nonvolatile)
Section 2
(50 cards)
bash
bourne again shell
green threads
a thread system implemented entirely at user-level without any reliance on operating system kernel services, other than those designed for single-threaded processes
CPU register
Internal memory in the CPU. These store information that the arithmetic and logic units need to carry out the current instruction.
race condition
an erroneous condition where the output of a function depends on the temporal order of events
client-server
A network architecture in which a system is divided between server tasks performed on the instructions received from clients, requesting information.
process
an instance of a running program on a computer; a unit of activity characterized by a single sequential thread of execution, a current state, and an associate set of allocated system resources
semaphore
a variable or abstract data type used to control access to a common resource by multiple processes in a concurrent system
stack
first in last out
process identifier (PID)
Most operating systems (including UNIX, Linux, and Windows) identify processes according to a unique integer number
two-level model
A variation on the many-to-many model that multiplexes many user-level threads to a smaller or equal number of kernel threads but also allows a user-level thread to be bound to a kernel thread.
multithreaded
Describes a program that is designed to have parts of its code execute concurrently
bounded buffer
problem for concurrent programming, arises from a situation when there is a speed disparity between processes, so data must be buffered between them; the producer is most often faster than the consumer
user thread
managed without kernel support and can be implemented on OS's that don't support threads. faster and more efficient than the other kind
shared memory
the memory that can be simultaneously accessed by multiple processes
ordinary pipes
allow two processes to communicate in standard producer-consumer fashion: the producer writes to one end of the pipe (the write-end) and the consumer reads from the other end parent/child relationship
sh
bourne shell
orphan
a process whose parent process has finished executing or terminated, this child process is then reclaimed by init
sandboxing
A form of software virtualization that lets programs and processes run in their own isolated virtual environment; in a browser, each tab & plugin run in its own address space, use IPC to communicate to main controller
kernel thread
The scheduler may decide to give more time to a processes that has a large number of these threads than a process that has a small number of threads, increasing efficiency
bootstrap program
A program stored in ROM that loads and initializes the operating system on a computer
fork()
returns 0 to indicate child process, returns the pid of the child to indicate parent process
policy
determines what will be done, more volatile
csh
C shell
system calls
the programmatic way in which a computer program requests a service from the kernel of the operating system it is executed on
Cache management
careful selection of the cache size and of a replacement policy can result in greatly increased performance
Message passing
in which packets of information in predefined formats are moved between processes by the operating system
data parallelism
distributing subsets of data across multiple processors
Shared memory
two or more processes read and write to a shared section of memory
many-to-many model
many kernel threads to many user threads
Long-term scheduler/Job scheduler
selects processes from this pool and loads then into memory for execution
mechanism
determines how to do something, less volatile
one-to-one model
one kernel thread to one user thread
Caching
faster storage system that keeps things on a temporary basis
message passing
allows multiple processes to read and write data to the message queue without being connected to each other. Messages are stored on the queue until their recipient retrieves them
cascading termination
The technique of terminating all child processes when a parent process terminates
task parallelism
threads working on shared data
named pipes
can be accessed without a parent-child relationship, can go two ways
Short-term scheduler/CPU scheduler
selects from among the processes that are ready to execute and allocates the CPU to one of them.
nash
not a shell
WORM
write once read many times
system call interface
the border between user mode and kernel mode that handles system calls
mutex lock
a program object that is created so that multiple program thread can take turns sharing the same resource
ksh
korne shell
critical section
a section of code that has a race-hazard in it, such that by preventing the interleaving of any other dependent code, the race condition will be avoided
blocking
a process waiting for some event, such as a resource becoming available or the completion of an I/O operation
many-to-one model
many user threads to one kernel thread
Cache coherency
a copy of A may exist simultaneously in several caches. Since the various CPUs can all execute in parallel, we must make sure that an update to the value of A in one cache is immediately reflected in all other caches where A resides.
Context switch
switching the CPU to another process requires performing a state save of the current process and a state restore of a different process
zombie
a process whose parent does not use the wait system call after a child dies to read its exit status
Amdahl's law
A system's speed is determined by its portion of code needed to be run serially speedup <= 1 / (S + (1-S)/N)
Section 3
(50 cards)
gdb
GNU debugger
cat
concatenate files and print on the standard output
|
output of a command as an input to another command (pipe)
mkdir
make directory
Types of System Calls
process control file management device management information maintenance communications
Shell Process Steps
shell startup cmd prompt waits for input parses input, interprets it returns to cmd prompt
OS Common Functionality
Multiprogramming Process management memory management storage management protection and security
CPU
Central Processing Unit; the brain of the computer.
vi
text editor (visual editor)
OS application layer
the libraries that are needed to run programs in that OS
man
manual
context-switch
The exchange of register information that occurs when one process is removed from the CPU and another takes its place
multitasking
the OS is responsible for suspending running processes
pwd
print working directory
&
job control
Non-Blocking I/O
returns immediately, indicating that data was read, or that the device was not ready. The process does not block
process isolation
technique to prevent and protect a process from inadvertent or malicious modification of its state by another process
<
takes input from file
Multiprogramming Problems
Improper process synchronization Failed mutual exclusion between processes Non-deterministic process execution Process deadlocks
Process
Unit of activity characterized by a single sequential thread of execution, a current state, and an associate set of allocated system resources
ls
list files in directory
cut
remove sections from each line of files
IPC
Inter Process Communication
process silo
grants each program the appearance of running on the hardware as if it were the only program on the system
Thirteen Layers of an OS
shell user processes directories devices file system communications virtual memory local secondary sore primitive processes interrupts procedures instruction set electronic circuits
gdb watch
watch for a variable change
ash
almquist shell
OS scheduler
handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy; chooses the next runnable process
cut --characters=LIST
remove only these characters from a file
mv
move a file or directory
ps
list processes
Kernel Startup Steps
setup hardware for OS enter protected mode initialize internal structures find and load its first program
Process States
New Running Waiting Ready Terminated
Waiting
process made a system call, result is not yet available
thread
a single stream of instructions being fetched by the processor only has one process identifier, PCB, memory address space, PC
valgrind
Tool to find memory issues
who
show who is logged on
gcc
compilation of a C program
rm
remove file
heap memory
an area of memory used for dynamic allocations, meaning that blocks of memory can be allocated and freed in an arbitrary order and accessed multiple times
whoami
print your userid
>
redirects output to a text file, stderr, etc.
multiple-processes
an alternative to non-blocking I/O A parent process can spawn new processes to handle the work loads Parent manages the workers
multiprogramming
admitting multiple processes to run-queue and switching between them giving the appearance that more than one program is running at the same time
Operating System
Create a program environment that gives the illusion that there is one program running on the system, and that that program has full control of the system, and is independent (or partially so) from all other programs running on the system
grep
searches for a pattern in each file1 file2 file3
OS user-interfaces
command line, GUIs, and required frameworks
computer components
CPU Memory Storage Busses Controllers Interface Boards User Hardware
less
opposite of more
data memory
the register of a CPU that contains the data to be stored in the computer storage (e.g. RAM), or the data after a fetch from the computer storage.
Section 4
(17 cards)