OS Flashcards
What is an Operating System?
An OS is a program or collection of programs that provides an easier, more convenient way for users to interact with hardware; it also manages hardware resources efficiently.
What are the main objectives of an Operating System?
Convenience for users, efficient management of resources, and ability to evolve with new requirements and technologies.
From the system’s perspective, what are the key roles of an OS?
Acts as a resource manager and a control system between user programs and hardware, preventing conflicts and misuse.
What components make up a computer system?
Hardware, Operating System, Application Programs, and Users.
What major services does an OS provide?
Program execution, I/O device access, file management, system access, error detection, and accounting/resource usage tracking.
Why was the need for an OS first realized?
Because even the fastest human operators were much slower than computers, leading to inefficient use of expensive hardware.
What was the role of a Monitor program in early batch systems?
It controlled the sequence of job execution, managed job control, interpreted batch languages, and always resided in memory.
What sacrifices were made when introducing simple batch systems?
Some processor time and main memory had to be devoted to the monitor program (overhead).
In what way does Multiprogramming improve CPU utilization?
While one job waits for I/O, the CPU can execute another job, reducing CPU idle time significantly.
Explain the concept of Time-Sharing Systems.
Multiple users interact with the computer at the same time, with the OS quickly switching between programs, giving the illusion of concurrency.
What happens during the booting process of a computer?
The firmware/bootloader initializes the system (CPU registers, memory), and loads the operating system kernel into RAM.
Why is firmware like BIOS stored in ROM or EEPROM?
Because these memories are non-volatile and protected, ensuring that crucial boot instructions persist even when power is off.
What are the four main functions of BIOS?
- POST (Power-On Self Test), 2. Bootstrap Loader, 3. Driver Initialization, 4. CMOS Setup.
What are interrupts, and why are they essential?
Interrupts are signals that cause the CPU to temporarily stop its current task and execute a service routine; they enable multitasking and responsive system behavior.
What happens during an interrupt handling routine?
The CPU saves its current state, jumps to the interrupt service routine (ISR), completes the ISR, and then resumes the interrupted task.
What is the difference between system calls and normal function calls?
System calls are requests made by programs to the OS to access privileged services; they pass through an API and transition from user mode to kernel mode.
What is Dual Mode operation, and why is it critical?
It separates user mode and kernel mode execution to protect the OS and hardware from user errors or malicious programs.
What is the purpose of a system call interface (API wrapper)?
It allows user programs to safely access OS services without directly executing privileged instructions, enhancing portability and safety.
What are the five main types of system calls?
- Process control, 2. File management, 3. Device management, 4. Information maintenance, 5. Communication.
What is virtual memory, and why was it introduced?
Virtual memory abstracts main memory to appear larger than it physically is, enabling programs larger than RAM to run efficiently.
