4 types of instruction
- Processor-memory,
- Processor-I/O
- data processing
- control
Types of interrupts
Program - Generated by some condition that is a result from an instruction execution
Timer - Generated by a timer within the processor that ca be programmed to trigger at regular interval or after a certain amount of time has passed
I/O - Generated by an I/O controller to signal completion of an operation or some other condition
Hardware failure - Generated by a failure in the hardware
Note: Can have sequential interrupts or nested interrupts (interrupts within interrupts)
Instruction Categories:
• Processor-memory: Instructions for transfer data between processor and memory.
• Processor-I/O: Instructions for
transferring data between
processor and peripheral devices through an I/O module.
• Data processing: Instructions for doing arithmetic or logical
operations on data.
• Control: Instructions that alter the sequence of execution.
What is the prupose of cache memory?
- Small and very fast memory between CPU and main memory.
- Invisible to the OS (just works)
- Can have several levels.
Why do we need an operating system at all? (Or do we really?)
The Stallings book describe three reasons for having an operating system
• Convenience
-The user interacts with the OS rather than hardware
• Efficiency
-Scheduler, control of memory and access of I/O resources
• Ability to evolve
-Must support new hardware, services and updates.
What is a process?
A process is an entity that can be assigned to and
executed by a processor.
What does a process consist of?
• The program code that defines what the process does.
• Basically the source code you write.
• Shared between all processes that execute the same
program.
• The set of data associated with the process.
• Each process has their own set of data.
• Stored in a process control block data structure.
• OS has to manage the data structures of the different
processes.
