System calls and their role in Operating Systems - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a system call?

A system call is a way for a program to ask the operating system to do something on its behalf, like reading a file or creating a new process.

beginner

Why do programs use system calls instead of directly accessing hardware?

Programs use system calls because the operating system controls hardware access to keep the system safe and stable. Direct access could cause errors or security problems.

intermediate

Name three common types of system calls.

Common system calls include: 1) File management (open, read, write), 2) Process control (create, terminate), 3) Communication (send, receive data).

intermediate

How does a system call work in simple terms?

When a program makes a system call, it switches from user mode to kernel mode so the operating system can safely perform the requested task, then returns control back to the program.

intermediate

What role do system calls play in multitasking operating systems?

System calls help manage multiple programs running at once by controlling process creation, scheduling, and communication between programs.

What is the main purpose of a system call?

A To request services from the operating system

B To directly control hardware devices

C To write code faster

D To bypass security checks

System calls allow programs to request services from the operating system safely.

Which mode does the CPU switch to when a system call is made?

A Safe mode

B User mode

C Kernel mode

D Sleep mode

The CPU switches to kernel mode to allow the operating system to perform privileged tasks.

Which of these is NOT a common system call category?

A Graphic design

B Process control

C File management

D Communication

Graphic design is not a system call category; system calls focus on managing files, processes, and communication.

Why can't user programs access hardware directly?

A Because hardware is broken

B To protect the system from errors and security risks

C Because hardware is too slow

D Because user programs are not smart enough

Direct hardware access is restricted to protect the system's stability and security.

What happens after the operating system completes a system call?

A The program crashes

B The program loses data

C The computer shuts down

D Control returns to the program in user mode

After the system call, control returns to the program running in user mode.

Explain what a system call is and why it is important in operating systems.

Think about how programs ask the OS to do things they cannot do themselves.

Describe the process that happens when a program makes a system call.

Focus on the mode change and how the OS handles the request.