DDK Glossary - I


 * IDC:Inter-device-driver communication.
 * in-memory buffer:A block of memory in the address space of the host machine, used for data transfer.
 * init time:See initialization time, device driver.
 * initialization time, device driver:After the OS/2 loads a device driver, it sends it an OS/2 request packet to initialize. During this initialization, certain DevHlp functions are not permitted. Also called init time.
 * Input/Output Control (IOCtl):A system service that provides a way for an application to send device-specific control commands to a device driver.
 * Input/Output Privilege Level (IOPL):Allows part of a Ring 3 application or device driver to execute at Ring 0.
 * input router:OS/2 internal process that removes messages from the system queue.
 * inter-device-driver communication (IDC):A mechanism that enables a physical device driver to communicate with another physical device driver.
 * interprocess communication:In the OS/2 operating system, the exchange of information between processes or threads through semaphores, queues, and shared memory.
 * interrupt:An instruction that directs the microprocessor to suspend what it is doing and run a specified routine. When the routine is complete, the microprocessor resumes its original work. See also routine.
 * interrupt request (IR):Broadly, an "interrupt request level", referring to pending or in-service interrupt requests, or to a specific level (for example, IR 4).
 * interrupt request flag:A bit in the 8259 PIC controller that indicates an interrupt is pending on particular level. The VPIC also maintains a virtual interrupt request flag for each interrupt level for each DOS session.
 * interrupt service flag:A bit in the 8259 PIC controller that indicates an interrupt request is being serviced. It is cleared when the PIC is sent EOI. The VPIC maintains a virtual interrupt service flag indicating that a simulated interrupt is in-progress in a DOS session.
 * interrupt time:When a device driver is run because of an interrupt rather than because of an application request. OS/2 device drivers receive interrupts either from the hardware they manage or from the system real-time clock. During interrupt time, certain DevHlp functions are not permitted. Also, addresses received directly from OS/2 applications might not be valid unless they are converted system addresses.
 * IOCtl:Input/Output Control.
 * IOPL:Input/Output Privilege Level.
 * IORB:Input/Output Request Block.
 * Input/Output Request Block (IORB):A data structure defined by this specification that is passed as a parameter on all calls to an adapter device driver. It contains a fixed section, followed by a command-dependent section.
 * IORBH:Input/Output Request Block Header
 * IRET:Interrupt return.
 * IRQ:Interrupt Request.