Definition

Noun: 1. A computer instruction that interrupts the currently executing program and transfers control to a supervisory program: This is a specific instruction in a computer's instruction set that causes the processor to switch from a user mode (where application programs run) to a more privileged supervisor or kernel mode. This allows the program to request services from the operating system's core, such as accessing hardware, allocating memory, or creating a new process.

Usage Examples

• Noun:
  • The application uses a supervisor call instruction to request more memory from the operating system.
  • When a program needs to read a file, it executes a supervisor call instruction to pass the request to the kernel.
  • Debugging tools often intercept supervisor call instructions to monitor a program's interaction with the OS.

Advanced Usage

• System Call Mechanism: The supervisor call instruction is the fundamental hardware mechanism that enables system calls. A program places arguments (e.g., a file name) in designated registers or on the stack and then executes this instruction to trigger the OS service.
• Trap/Exception: This instruction is a type of software-generated trap or exception. It is a planned interruption initiated by the program itself, as opposed to an interrupt caused by an external hardware event.
• Context Switch: Executing this instruction typically triggers a context switch, where the processor saves the state of the user program, switches to a privileged execution mode, and begins running kernel code.

Variants and Related Words

• System Call (n): The high-level programming interface or function (e.g., , ) that a programmer uses, which is ultimately implemented using a supervisor call instruction. They are often used interchangeably, though "system call" is more common in software development, while "supervisor call instruction" is more specific to computer architecture.
• Trap Instruction (n): A broader category of instructions that cause a synchronous switch to a handler; a supervisor call is a specific type of trap.
• SVC (n): Abbreviation commonly used in some processor architectures (e.g., ARM) for "Supervisor Call," which is the mnemonic for this instruction.
• syscall (n): A common abbreviation and instruction mnemonic in other architectures (e.g., x86-64) for "system call."

Synonyms

• Software Interrupt: Emphasizes its nature as an interrupt generated by software.
• Kernel Call: Highlights the destination of the call (the OS kernel).

Related Phrases

• To invoke a supervisor call: To execute the instruction, initiating the switch to kernel mode.
  • The library function invokes a supervisor call to perform the actual I/O operation.
• To handle a supervisor call: The action performed by the operating system's trap handler when the instruction is executed.
  • The kernel's trap handler handles the supervisor call by checking the request number and calling the appropriate service routine.

Noun

1. an instruction that interrupts the program being executed and passes control to the supervisor