System calls and their role in Operating Systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of a system call?

System calls allow user programs to:

A Directly access hardware devices without restrictions

B Request services from the operating system kernel

C Modify the source code of the operating system

D Run programs without using the CPU

💡 Hint

Think about how user programs interact with the operating system.

System calls provide a controlled way for user programs to ask the operating system to perform tasks on their behalf, such as reading files or creating processes.

📋 Factual

intermediate

Which of the following is NOT typically a system call?

Identify the option that is generally not implemented as a system call in operating systems.

A Allocating memory dynamically within a program

B Opening a file

C Creating a new process

D Sending data over a network socket

💡 Hint

Consider which actions require kernel intervention versus those handled by the program itself.

Dynamic memory allocation (like malloc in C) is usually handled by the program's runtime library, not directly by system calls.

🔍 Analysis

advanced

Why do system calls involve a context switch between user mode and kernel mode?

Explain the reason behind switching modes during a system call.

A To allow the CPU to run multiple programs simultaneously

B To speed up the execution of user programs

C To protect the system by controlling access to hardware and resources

D To enable direct hardware manipulation by user programs

💡 Hint

Think about security and stability in operating systems.

The switch to kernel mode ensures that only trusted code can perform sensitive operations, protecting the system from accidental or malicious damage.

❓ Comparison

advanced

Compare system calls and library functions in terms of their interaction with the operating system.

Which statement correctly describes the difference between system calls and library functions?

A Library functions may call system calls internally to perform OS-level tasks

B System calls do not require switching to kernel mode, but library functions do

C System calls are implemented in user space, while library functions run in kernel space

D Library functions always provide direct hardware access without OS involvement

💡 Hint

Consider how libraries use system calls to interact with the OS.

Library functions often provide convenient interfaces and internally invoke system calls to request OS services.

❓ Reasoning

expert

What would likely happen if user programs could perform system calls without switching to kernel mode?

Consider the consequences if system calls executed entirely in user mode.

A The system would be more secure because user programs control hardware directly

B System calls would run faster without any risks

C There would be no change in system behavior or security

D User programs could cause system crashes or security breaches easily

💡 Hint

Think about the role of kernel mode in protecting the system.

Allowing system calls in user mode would remove protections, letting programs access hardware and memory directly, risking crashes and security issues.