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Questions and Answers
What term refers specifically to a program that is currently being executed in an operating system?
Which component is NOT typically included in a process's structure in memory?
In the context of operating systems, what does job scheduling primarily involve?
What does the stack of a process contain?
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Which of the following best describes the importance of a program counter in a process?
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What state indicates that a process is currently executing instructions?
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Which of the following is NOT a piece of information typically found in a process control block (PCB)?
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In which process state is a process waiting for some event to occur?
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Which information in the PCB is crucial for resuming a process after an interrupt?
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What does the CPU-scheduling information in a PCB typically include?
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Which of the following best describes a situation when a process is in the 'ready' state?
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What type of information might be included in the memory-management part of a PCB?
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Which of the following states indicates that a process has finished execution?
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What happens to an activation record when control is returned from a function?
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Which of the following correctly describes the difference between a program and a process?
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How do the stack and heap sections grow in a programming environment?
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What initiates the execution of a program in an operating system?
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In what scenario can multiple processes be associated with the same program?
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What role does the Java Virtual Machine (JVM) play in executing Java programs?
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What must the operating system manage to prevent memory overlap between the stack and heap?
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What is responsible for keeping track of the next instruction to execute in a process?
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Study Notes
Operating System terminology
- While "process" is the preferred term for a program in execution, it is acceptable to use "job" in certain contexts, particularly for describing the role of the operating system.
- Using terms like "job scheduling" is not misleading, even though "process" is a more modern term.
Process Structure and Execution
- An operating system executes various programs, referred to as "jobs" in batch systems and "user programs" or "tasks" in time-shared systems.
- A "process" represents a program in execution.
- Process execution proceeds sequentially.
- A process consists of more than just program code (text section).
- It also includes the current activity, represented by the program counter and processor registers.
- Other components of a process include:
- Process stack: Contains temporary data like function parameters, return addresses, and local variables.
- Data section: Stores global variables.
- Heap: Dynamically allocated memory during process runtime.
Memory Management
- The text and data sections of a program have a fixed size and do not change during program runtime.
- The stack and heap sections can grow and shrink dynamically as the program executes.
- The stack grows when a function is called and shrinks when control is returned, and it stores function parameters, local variables, and the return address.
- The heap grows with dynamic memory allocation and shrinks when memory is released.
- The heap and stack grow towards each other but the operating system ensures they do not overlap.
Processes vs. Programs
- A program is a passive entity, like an executable file stored on disk, containing instructions.
- A process is an active entity formed when a program is loaded into memory, with a program counter and other resources.
Process Creation and Execution
- A program becomes a process when the executable file is loaded into memory.
- A process can be started by user interaction, such as clicking on an icon, or by entering a command in the command line.
- Several processes can run the same program, each with its own execution sequence and unique data, heap, and stack sections.
Process Attributes
- Processes are represented in the operating system by a Process Control Block (PCB), also known as a Task Control Block.
- The PCB contains information about the process, including:
- Process State: new, running, waiting, ready, or terminated.
- Program Counter: the address of the next instruction.
- CPU Registers: accumulators, index registers, stack pointers, and general-purpose registers.
- CPU Scheduling Information: priority, pointers to scheduling queues, and scheduling parameters.
- Memory Management Information: base and limit registers, page tables, or segment tables.
- Accounting Information: CPU and real time used, time limits, account numbers, job or process numbers.
- I/O Status Information: list of I/O devices allocated, open files.
Java Virtual Machine
- The Java Virtual Machine (JVM) is a process that interprets and runs compiled Java code.
- Java programs are usually executed within the JVM.
- The JVM simulates the execution of Java code by translating it into native machine instructions.
- Executing a Java program, like "java Program", runs the JVM process, which then executes the Java program "Program.class".
Process States
- new: The process is being created.
- running: Instructions are being executed.
- waiting: The process is waiting for an event to occur.
- ready: The process is waiting to be assigned to a processor.
- terminated: The process has finished execution.
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Description
This quiz covers key terminology related to operating systems, focusing on concepts such as processes, jobs, and their execution within different systems. Understand how processes are structured and the components that make up a process. Test your knowledge on important terms and the functioning of operating systems.
