processes.xps

Question 1

Early computer system allowed only…?

Answer 1

one program to be executed at a time. This program had complete control of the system and had access to all the system’s resources.

Question 2

Current day computer system allow…?

Answer 2

multiple programs to be loaded into memory and executed concurrently. This evolution required firmer control and more compartmentalization of the various programs, and these needs resulted in the notion of a process.

Question 3

A process is …?

Answer 3

a program in execution . A process is the unit of work in a modern time-sharing system.

Question 4

The more complex the OS is, the more it is…?

Answer 4

expected to do.

Question 5

its main concern is …?

Answer 5

the execution of user programs, it also needs to take care of various system tasks that are better left outside the kernel itself.

Question 6

A system consists of a…?

Answer 6

collection of processes.

(OS processes executing system code and user processes executing user code.)

Potentially, all these processes can execute concurrently, with the CPU (or CPUs) multiplexed among them.

Question 7

By switching the CPU between process, the OS can make the computer…?

Answer 7

more productive.

Question 8

A batch system executes jobs, whereas a time-shared system has…?

Answer 8

user programs, or tasks. Even on a single-user system such as the original MS Windows, a user may be able to run several programs at one time: a word processor, a Web browser, and an e-mail package. And even if the user can execute only one program at a time, the OS may need to support its own internal programmed activities, such as memory management. In many respect, all these activities are similar, so we call all of them processes.

The terms job and process are used almost interchangeably in this text. Although we personally prefer the term process, much of OS theory and terminology was developed during a time when the major activity of OSs was job processing. It would be misleading to avoid the use of commonly accepted terms that include the word job (such as job scheduling) simply because process has superseded job.

Question 9

A process is more than the program code, which is sometimes known as the…?

Answer 9

text section.

Question 10

Processes also includes the current activity, as represented by the value of….?

Answer 10

the program counter and the contents of the processor’s registers.

Question 11

A process generally also includes the process stack, which contains…?

Answer 11

temporary data (such as function parameters, return addresses, and local variables), and a data section, which contains global variables.

Question 12

A process may also include a heap, which is…?

Answer 12

memory that is dynamically allocated during process run time.

Question 13

We emphasize that a program by itself is not a…?

Answer 13

process.

Question 14

A program is a …?

Answer 14

pass entity, such as a file containing a list of instructions stored on disk (often called an executable file), where as a process is an active entity, with a program counter specifying the next instruction to execute a set of associated resources.

Question 15

A program becomes a process when an…?

Answer 15

executable file is loaded into memory.

Question 16

Two common techniques for loading executable files are …?

Answer 16

double clicking an icon representing the executable file and entering the name of the executable file on the command line (as in prog.exe or a.out)

Question 17

Although two processes may be associated with the same program, they are nevertheless considered…?

Answer 17

two separate execution sequences. (For instance, several users may be running different copies of the mail program, or the same user may invoke many copies of the Web browser program. Each of these separate process, and although the text sections are equivalent, the data, heap, and stack sections vary. It is also common to have a process that spawns many processes as it runs)

Question 18

As a process executes it changes…?

Answer 18

State.

Question 19

The state of a process is defined in part by the…?

Answer 19

current activity of that process.

Question 20

Each process may be in one of the following states….?

Answer 20

• New: The process is being created.
• Running : Instructions are being executed.
• Waiting : The process is waiting for some event to occur (such as an I/O completion or reception of a signal).
• Ready : The Process is waiting to be assigned to a processor.
• Terminated : The process has finished execution.

(These names are arbitrary, and they vary across OS. The states that they represent are found on all systems, however. Certain os also delineate process states more finely. It is important to realize that only one process can be running on any processor at any instant. Many processes may be ready and waiting, however

Question 21

Each process is represented in the OS by a…?

Answer 21

process control block. (PBC)

Question 22

A process control block is also called…?

Answer 22

a task control block.

Question 23

Process state…?

Answer 23

the state may be new, ready, running, waiting, halted, and so on.

Question 24

Program counter…?

Answer 24

The counter indicates the address of the next instruction to be executed for this process.

Question 25

CPU reigisters…?

Answer 25

The registers vary in number and type, depending on the computer architecture. They include accumulators, index registers, stack pointers, and general-purpose registers,plus any condition code information. Along with the program counter, this state information must be saved when an interrupt occurs, to allow the process to be continued correctly afterwards.

Question 26

CPU-scheduling…?

Answer 26

this information includes a process priority, pointers to scheduling, queues, and any other scheduling parameters.

Question 27

Memory-management information…?

Answer 27

this information may include such information as the value of the base and the limit registers, the page tables, or the segment tables, depending on the memory system used by the OS.

Question 28

Accounting information…?

Answer 28

This information includes the amount of CPU and real time used, time limits, account numbers , job or process numbers, and so on.

Question 29

I/O status information…?

Answer 29

This information includes the list of I/O devices allocated to the process, a list of open files, and so on.

Question 30

PCB simply serves as the repository for any information that…?

Answer 30

may vary from process to process.

Question 31

A process is a program that performs a single…?

Answer 31

thread of execution.

For example, when a process is running a word-processing program, a single thread of instructions is being executed.

Question 32

The single thread of control allows the process to?

Answer 32

preform only one task at a time.

(The user cannot simultaneously type in characters and run the spell checker within the same process, for example. Many modern os have extended the process concept to allow a process to have multiple threads of execution and thus to perform more than one task at a time.

Question 33

On a system that supports threads, the PCB is expanded to include…?

Answer 33

information for each thread. Other changes throughout the system are also needed to support threads.

Question 34

The objective of multiprogramming is to…?

Answer 34

have some process running at all times, to maximize CPU utilization.

Question 35

The objective of time sharing is to…?

Answer 35

switch the CPU among processes so frequently that users can interact with each program while it is running.

Question 36

to help with question 34 and 35 the process scheduler selects an available process (possibly from a set of several available process) for…?

Answer 36

program execution on the CPU.

Question 37

For a single processor system, there will never be…?

Answer 37

more than one running process.

(If there are more processes, the rest will have to wait until the CPU is free and can be rescheduled.

Question 38

As a process enters the system, the are put into a…?

Answer 38

job queue.

Question 39

The job queue consists of …?

Answer 39

all processes in the system.

Question 40

The processes that are residing in main memory and are all ready and waiting to execute are kept on…?

Answer 40

a list called the ready queue.

Question 41

The ready queue is generally stored as…?

Answer 41

a link list.