Operating Systems for Computer Scientists (chapter 1)

hardware

The CPU, memory devices, input/output (I/O) devices, and any other physical components that are part of a computer.

application program

A program designed for end-user execution, such as a word processor, spreadsheet, compiler, or Web browser.

ease of use

The amount of difficulty and complexity involved in using some aspect of computing.

resource utilization

The amount of a given resource (hardware or software) that is being used.

touch screen

A touch-sensitive screen used as a computer input device.

voice recognition

A computer interface based on spoken commands, which the computer parses and turns into actions.

Siri

The Apple voice-recognition system.

embedded computer

A computer system within some other, larger system (such as a car) that performs specific, limited functions and has little or no user interface.

resource allocator

An operating system or application that determines how resources are to be used.

control program

A program that manages the execution of user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.

Moore's Law

A law predicted that the number of transistors on an integrated circuit would double every eighteen months/ the idea that the number of parts on a computer chip doubles about every 18 months  

kernel

The operating system component running on the computer at all times after system boot.

system program

A program associated with the operating system but not necessarily part of the kernel.

middleware

A set of software frameworks that provide additional services to application developers.

bus

A communication system; e.g., within a computer, a bus connects various components, such as the CPU and I/O devices, allowing them to transfer data and commands.

device driver

An operating system component that provides uniform access to various devices and manages I/O to those devices.

interrupt

A hardware mechanism that enables a device to notify the CPU that it needs attention.

interrupt vector

An operating-system data structure indexed by interrupt address and pointing to the interrupt handlers. A kernel memory data structure that holds the addresses of the interrupt service routines for the various devices.

interrupt-request line

The hardware connection to the CPU on which interrupts are signaled

interrupt-handler routine

An operating system routine that is called when an interrupt signal is received.

interrupt-controller hardware

Computer hardware components for interrupt management.

nonmaskable interrupt

An interrupt that cannot be delayed or blocked (such as an unrecoverable memory error)

maskable

Describes an interrupt that can be delayed or blocked (such as when the kernel is in a critical section).

interrupt chaining

A mechanism by which each element in an interrupt vector points to the head of a list of interrupt handlers, which are called individually until one is found to service the interrupt request.

interrupt priority level

Prioritization of interrupts to indicate handling order.

random-access memory (RAM)

Rewritable memory, also called main memory. Most programs run from RAM, which is managed by the kernel.

dynamic random-access memory (DRAM)

The common version of RAM, which features high read and write speeds

bootstrap program

The program that allows the computer to start running by initializing hardware and loading the kernel.

volatile

Describes storage whose content can be lost in a power outage or similar event.

firmware

Software stored in ROM or EEPROM for booting the system and managing low level hardware.

bit

The basic unit of computer storage. A bit can contain one of two values, 0 or 1.

byte

Eight bits

word

A unit made up of one or more bytes. For example, a computer that has 64-bit registers and 64-bit memory addressing typically has 64-bit (8-byte) words.

kilobyte (KB)

1,024 bytes

megabyte (MB)

1,024^2 bytes

gigabyte (GB)

1,024^3 bytes

terabyte (TB)

1,024^4 bytes.

petabyte (PB)

1,024^5 bytes.

von Neumann architecture

The structure of most computers, in which both process instructions and data are stored in the same main memory.

secondary storage

A storage system capable of holding large amounts of data permanently; most commonly, HDDs and NVM devices.

hard disk drive (HDD)

A secondary storage device based on mechanical components, including spinning magnetic media platters and moving read-write heads.

nonvolatile memory (NVM)

Persistent storage based on circuits and electric charges.

tertiary storage

A type of storage that is slower and cheaper than main memory or secondary storage; frequently magnetic tape or optical disk.

semiconductor memory

The various types of memory constructed from semiconductors

memory

Volatile storage within a computer system

nonvolatile storage (NVS)

Storage in which data will not be lost in a power outage or similar event

nonvolatile memory (NVM)

Persistent storage based on circuits and electric charges.

direct memory access (DMA)

A resource-conserving and performance-improving operation for device controllers allowing devices to transfer large amounts of data directly to and from main memory.

bus

a pathway that moves data and instructions between parts of a computer, like the CPU and devices 

device driver

software that helps the operating system talk to and control hardware like printers or keyboards 

interrupt

a signal from a device telling the computer’s brain (the CPU) that something important needs attention right away

interrupt vector

a list that shows where the computer should go to handle different kinds of interruptions 

interrupt-request line

a wire or circuit that lets devices send signals to the CPU to ask for attention  

interrupt-handler routine

a special program that the computer runs when it gets an interrupt signal  

interrupt-controller hardware

parts of the computer that manage when and how interrupts are handled  

non-maskable interrupt

an urgent signal that the CPU must deal with immediately, like a major error 

maskable

describes an interrupt that the CPU can choose to ignore briefly, usually when it’s busy doing something very important

interrupt chaining

a method where the computer checks a list of programs to find the right one to handle an interrupt  

interrupt priority level

a way of deciding which interrupts are most urgent, so that the computer can handle them in the right order

random-access memory (RAM)

a computer's main memory that can be used quickly to run programs 

dynamic random-access memory (DRAM)

a type of RAM that is fast and used a lot in computers  

volatile

describes memory that loses its information when the computer turns off 

electrically erasable programmable read-only memory (EEPROM)

a type of nonvolatile memory that can be electrically erased and reprogrammed to store data 

bootstrap program

the first program that starts a computer by getting everything ready for the main software to run when the computer is turned on 

bit

the smallest unit of data storage containing one of two values, 0 (off) or 1 (on) 

byte

eight bits  

word

a unit of data representing multiple bytes, such as 4 bytes in a 32-bit system or 8 bytes in a 64-bit system 

hard disk drive (HDD)

a storage device that uses spinning disks and read/write heads to store and retrieve data 

nonvolatile memory (NVM)

memory that retains data even when power is turned off 

nonvolatile storage (NVS)

storage that keeps data without needing power, such as hard drives and SSDs

solid state drive (SSD)

a storage device that uses flash memory to store data with no moving parts 

big data

Extremely large sets of data; distributed systems are well suited to working with big data.

MapReduce

A Google-created big data programming model and implementation for parallel processing across nodes in a distributed cluster. A layer on top of the Google file system (GFS), it allows developers to carry out large-scale parallel computations easily.

system daemon

A service that is provided outside the kernel by system programs that are loaded into memory at boot time and run continuously.

trap

A software interrupt. The interrupt can be caused either by an error (e.g., division by zero or invalid memory access) or by a specific request from a user program that an operating-system service be performed.

exception

A software-generated interrupt caused either by an error (such as division by zero or invalid memory access) or by a specific request from a user program than an operating-system service be performed.

system call

Software-triggered interrupt allowing a process to request a kernel service.

multiprogramming

A technique that increases CPU utilization by organizing jobs (code and data) so that the CPU always has a job to execute.

process

A program loaded into memory and executing.

multitasking

The concurrent performance of multiple jobs. A CPU executes multiple jobs by switching among them, but the switches occur so frequently that users can interact with the processes.

response time

The amount of time it takes the system to respond to user action.

CPU scheduling

The process by which the system chooses which job will run next if several jobs are ready to run at the same time.

virtual memory

A technique that allows the execution of a process that is not completely in memory. Also, separation of computer memory address space from physical into logical, allowing easier programming and larger name space.

logical memory

Memory as viewed by the user; usually a large uniform array, not matching physical memory in virtual memory systems.

user mode

A CPU mode for executing user processes in which some instructions are limited or not allowed. See also kernel mode.

kernel mode

A CPU mode in which all instructions are enabled. The kernel runs in this mode. See also user mode.

supervisor mode

A CPU mode in which all instructions are enabled. The kernel runs in this mode. See also user mode.

system mode

A CPU mode in which all instructions are enabled. The kernel runs in this mode. See also user mode.

privileged mode

A CPU mode in which all instructions are enabled. The kernel runs in this mode. See also user mode.

mode bit

A CPU status bit used to indicate the current mode: kernel (0) or user (1).

privileged instructions

Instructions that can execute only if the CPU is in in kernel mode.

protection rings

A model of privilege separation consisting of a series of rings, with each successive ring representing greater execution privileges.

virtual machine manager (VMM)

The computer function that manages the virtual machine; also called a hypervisor.

timer

A hardware component that can be set to interrupt the computer after a specified period.

batch operating system

executes similar jobs in batches to optimize CPU use without user interaction 

multiprogramming

keeps multiple programs in memory to maximize CPU usage by switching between them

main memory management

the process of handling the system's primary memory (RAM) to ensure efficient use by programs 

CPU scheduling

the method used by an operating system to decide which process gets to use the CPU and for how long

time-sharing system

an operating system that allows multiple users to share computer resources simultaneously 

multitasking

the ability of an operating system to run multiple tasks or programs at the same time