The two main functions of a basic OS are
a. Hardware Abstraction and
b. Resource Management.
True
False
True is the answer.
Hardware abstraction and resource management are the two fundamental functionalities of a basic OS.
Hardware abstraction refers to the OS acting as an intermediary between the physical hardware components (CPU, memory, storage) and the software applications. It provides a standardized interface that applications can use to interact with the hardware, regardless of the specific underlying hardware details. This simplifies application development and makes the system more portable across different hardware platforms.
Resource management involves the OS efficiently allocating and controlling resources like CPU time, memory, storage space, and I/O devices. The OS ensures that multiple applications can share these resources fairly and prevents any single application from monopolizing them. This optimizes system performance and stability.
Match the following:
A- Contiki OS i. OS with Secure Environment
B- Fedora ii. Server OS
C- Redhat iii. Desktop OS
D- QNX iv. Embedded OS
E- Sel4 v. Mobile OS
F- Symbian vi. Real Time OS
Here's the matching with explanations:
A- Contiki OS iv. Embedded OS
B- Fedora iii. Desktop OS
C- Redhat ii. Server OS (with a caveat)
D- QNX iv. Embedded OS
E- Sel4 vi. Real Time OS (microkernel)
F- Symbian v. Mobile OS (discontinued)
Contiki OS is a lightweight operating system designed for resource-constrained devices like sensor networks and wearables. It prioritizes low power consumption and a small footprint, making it ideal for embedded systems.
Fedora is a popular open-source Linux distribution known for its focus on innovation and user experience. It's primarily used as a desktop operating system.
Redhat offers a commercial, enterprise-focused Linux distribution widely used for servers due to its stability, security features, and long-term support. However, Redhat also has a workstation variant usable as a desktop OS.
QNX is a real-time operating system designed for embedded systems with strict timing requirements, often found in industrial automation and automotive applications.
Sel4 is a high-assurance microkernel operating system known for its focus on security and real-time performance. It's used in various embedded systems requiring high security and predictability.
Symbian was a popular mobile operating system used on smartphones in the early 2000s but has since been discontinued.
BIOS is a part of extended memory that is loaded every time the system boots up.
True
False
False
The statement is incorrect for two reasons:
BIOS location: BIOS (Basic Input/Output System) is firmware, not part of the main system memory. It's stored in a separate, non-volatile memory chip like ROM (Read-Only Memory) or flash memory on the motherboard. This ensures the BIOS code persists even after the system powers off and is readily available for booting up the system.
Loading vs. execution: BIOS isn't "loaded" every time the system boots. It's already present in the dedicated memory chip. During bootup, the power-on self-test (POST) procedure executed by the BIOS checks system hardware functionality and then loads the operating system from a storage device like a hard drive.
Global and Static data is always maintained in the text section of the memory
True
False
False
Global and static data are not always stored in the text section of memory. Here's a breakdown of where they typically reside:
Global Variables:
Typically stored in a special data segment of the program's binary. This segment is loaded into memory alongside the program code (text section) during execution.
Static Variables:
The location depends on the scope:
Static within a function: These behave similarly to global variables and reside in the data segment.
Static at file scope (outside any function): These might be placed in the data segment or the text segment depending on the programming language and compiler implementation.
Text Section:
The text section stores the program's actual instructions (code) that the CPU executes. It's read-only memory.
Data Segment:
This section holds initialized global and static variables along with other data the program needs during execution. It's read-write memory.
In summary, while global and static data often reside near the program code for efficiency, they are not strictly within the text section itself, which is reserved for instructions.
malloc(sizeof(int)) returns
A void pointer pointing to a memory of size of 1 unit of integer type allocated in stack.
An integer pointer pointing to a memory of size of 1 unit of integer type.
An integer pointer pointing to a memory of size of 1 unit of integer type.
A void pointer pointing to a memory of size of 1 unit of integer type allocated in heap.
The correct answer is:
C. An integer pointer pointing to a memory of size of 1 unit of integer type allocated in heap.
Here's a breakdown of why this is the answer:
malloc: This is a function in C used for dynamic memory allocation on the heap. The heap is a memory region that grows and shrinks during program execution as needed to store dynamically allocated data.
sizeof(int): This expression calculates the size of an integer data type in bytes on the specific system architecture the program is running on.
Return type: While malloc itself returns a void* pointer (generic pointer), it's good practice to cast it to the specific pointer type you're allocating memory for. In this case, casting to int* indicates the pointer points to an integer location.
Memory allocation: The malloc function allocates a contiguous block of memory on the heap large enough to hold a single integer (sizeof(int) bytes).
Therefore, the overall statement describes that malloc(sizeof(int)) returns an integer pointer pointing to a newly allocated memory block on the heap, sized to hold one integer value.
Any procedural call will always use a TRAP instruction to carry out the execution in kernel space.
True
False
False
Not all procedural calls use TRAP instructions to enter kernel space. Here's why:
Procedural Calls: These are mechanisms for transferring control flow between different parts of a program. They can be within user space (between functions in the same program) or involve system calls (user program requesting kernel services).
TRAP Instructions: These are special instructions that trigger a processor interrupt, causing the CPU to temporarily halt the current program and switch to executing kernel-level code (specifically, a trap handler).
Types of Procedural Calls:
Regular Function Calls: These calls within user space typically don't involve TRAP instructions. The CPU manages the call stack and program counter to transfer control to the called function's code segment and return when finished.
System Calls: When a user program needs to access privileged resources or services provided by the kernel (e.g., reading a file), it executes a system call instruction (often a specific TRAP instruction). This triggers a context switch to kernel space, where the kernel handles the request and switches back to user space upon completion.
In essence, TRAP instructions are used specifically for system calls, which are a subset of all procedural calls. Not all function calls within a program require entering kernel space and thus wouldn't use TRAP instructions.
Monolithic Kernels Linux, xv6 are great because they are easy to maintain, have large size and less bugs.
True
False
False is a more accurate answer.
While Linux and xv6 (a teaching operating system based on Linux) have some advantages, the statement contains misconceptions about monolithic kernels.
Here's a breakdown:
Maintainability: Monolithic kernels can be complex due to their large size and tightly coupled components. Debugging and isolating issues can be challenging compared to modular architectures.
Size: Monolithic kernels are indeed large as they integrate various functionalities like device drivers, memory management, and process scheduling. While size can offer performance benefits, it can also lead to complexity.
Bugs: The sheer size of a monolithic kernel can statistically increase the likelihood of bugs existing. However, mature kernels like Linux have extensive testing and development processes to minimize bugs.
Advantages of Monolithic Kernels:
Performance: Tight integration between system components can lead to efficient communication and faster execution.
Simplicity: The concept is relatively easier to grasp compared to microkernels.
Disadvantages of Monolithic Kernels:
Maintainability: As mentioned earlier, complexity can make maintenance and debugging more challenging.
Flexibility: Adding new features requires modifying the kernel itself, potentially impacting stability.
Security: A bug in a critical kernel component can compromise the entire system.
In conclusion, while Linux and xv6 are well-regarded monolithic kernels, their size doesn't necessarily equate to ease of maintenance or fewer bugs. They offer performance benefits but may be less modular and flexible compared to other architectures.
IPC is a primary feature of micro Kernels
True
False
True is the answer.
Inter-process communication (IPC) is a fundamental feature of microkernels. Here's why:
Microkernel Design: Microkernels are designed with a minimalist approach, focusing on core functionalities like memory management, thread management, and most importantly, IPC.
Separation of Concerns: In a microkernel architecture, device drivers and other services like the file system operate in user space as separate processes. These processes need to communicate with each other and the microkernel to exchange data and requests.
IPC Mechanisms: Microkernels provide various IPC mechanisms like message passing or shared memory to facilitate communication between processes. These mechanisms allow processes to exchange information and synchronize their execution.
Communication in Microkernels:
Unlike monolithic kernels where processes can directly interact with kernel services, in microkernels, processes communicate by sending messages or manipulating shared memory regions through the microkernel. This mediated communication enforces isolation and security between processes.
Impact of IPC:
While IPC offers advantages in security and modularity, it can introduce some performance overhead compared to direct function calls within a monolithic kernel. This is because communication involves context switches between processes and the microkernel.
Overall, IPC is a cornerstone of microkernels, enabling communication and resource sharing between processes in a secure and modular fashion.
Hyperthreading is used to parallelize the work by the OS among the different CPU cores
True
False
False
Hyperthreading is not used to parallelize work among different CPU cores. Here's the clarification:
Hyperthreading Technology: It's a technology by Intel (similar technologies exist with other names from other manufacturers) that allows a single physical CPU core to appear as two logical cores to the operating system.
Focus of Hyperthreading: It aims to improve the efficiency of a single core by allowing it to handle multiple threads concurrently. This is useful when a single process has multiple independent tasks (threads) that can be executed somewhat independently.
Parallelization Across Cores:
True parallelization of work across multiple cores relies on multi-core processors. These processors have distinct physical cores that can execute instructions simultaneously.
The operating system schedules tasks (processes and threads) across these cores to utilize the available processing power effectively.
Impact of Hyperthreading:
Hyperthreading allows a single core to handle multiple threads, potentially improving performance for workloads that benefit from multithreading.
However, it doesn't create additional physical cores and cannot parallelize tasks that require exclusive core access for heavy computations.
In essence, hyperthreading deals with improving the efficiency of a single core, while multi-core processors handle true parallelization across cores.
I. OS encourages Race Condition to occur during execution of processes as it ensures efficient utilization of resources
II. OS avoids synchronization as it slows down the performance and causes deadlock
I - True II - True
I- False II - False
I- True II- False
I- False II - True
The answer is: I- False II - False
Here's the breakdown of why both statements are incorrect:
I. OS encourages Race Condition:
Race Condition: This is an undesirable scenario where the outcome of a program's execution depends on the unpredictable timing of events, often caused by multiple processes or threads accessing shared resources concurrently without proper synchronization. It can lead to errors and unexpected behavior.
OS Role: A well-designed operating system aims to prevent race conditions by providing mechanisms like mutexes and semaphores for process/thread synchronization when accessing shared resources. This ensures predictable and reliable program execution.
II. OS avoids synchronization:
Synchronization: Synchronization is crucial for ensuring correct and consistent execution of processes or threads that access shared resources. It avoids race conditions and data corruption.
OS Role: Operating systems provide synchronization primitives like mutexes, semaphores, and critical sections to coordinate access to shared resources. While some overhead is involved, it's necessary to maintain system stability and data integrity. Deadlocks can occur due to improper synchronization, but the OS aims to avoid them using deadlock detection and prevention techniques.
In conclusion, a well-designed OS strives to prevent race conditions through synchronization and provides mechanisms to avoid deadlocks. Both synchronization and efficient resource utilization are important goals for an OS, and they are not mutually exclusive.