Question

System calls are usually invoked by using which one of the following means?

• A. A privileged instruction
• B. A jump instruction
• C. Software interrupt
• D. Hardware interrupt

Hint:

System calls rely on software-generated interrupts or traps, not hardware interrupts.

Answer 1

The Correct Option is C

Step 1: Understanding system calls.
System calls provide an interface between user programs and the operating system kernel, allowing controlled access to system resources.
Step 2: How system calls are triggered.
User programs cannot directly execute kernel-level instructions. Instead, they trigger a controlled transfer of control to the kernel.
Step 3: Role of software interrupts.
This transfer is typically achieved using a software interrupt or trap instruction, which switches the CPU from user mode to kernel mode.
Step 4: Final conclusion.
Hence, system calls are usually invoked using software interrupts.