In computers, especially IBM mainframes, a supervisor call (SVC) is a processor instruction that directs the processor to pass control of the computer to the operating system's supervisor program. Most SVCs are requests for a specific operating system service from an application program or another part of the operating system. Application program developers usually use a language function or macro instruction to make the request (for example, to get allocated more memory for the program to work with). The language compiler or assembler generates the instruction that includes the specific SVC request. Each service has a preassigned SVC number. When the computer's processor executes the instruction that contains the SVC, the code representing "SVC" causes a program interrupt to occur, which means that control of the processor is immediately passed to the operating system supervisor program. The supervisor then passes control to programming that performs the service that goes with the specified SVC number.Content Continues Below
An SVC routine is a program within the supervisor that performs the service indicated by the specific SVC instruction.