Lecture 1 Flashcards
Examples of Computer Hardware
CPU, RAM, Storage
Operating Systems enable…
…the user to interact with hardware
Examples of System/Application Programs
Compilers, Text Editors, Database Management Systems
Operating Systems act as…
…Resource allocators and control programs
What useful functions do operating systems provide on their own?
None (Waits for user or programs to do something)
Resource Allocator
- Manages all resources
- Decides between conflicting requests for efficient/fair
resource use
Control Program
Prevents errors and improper use of the computer
Operating System Goals
- Make system convenient to use (more important for
PCs) - Use hardware efficiently (more important for shared
systems) - Sacrifice performance to improve lifetime of resources
(Only done sometimes)
CPUs and device controllers connect through a bus to…
…Shared memory, which becomes a means of communication
Steps of an I/O operation
- CPU sends read request (CPU and I/O device
controllers execute concurrently) - Incoming data written to I/O device’s local buffer
- When I/O complete, send CPU an interrupt
- CPU services interrupt, read from I/O local buffer to
main memory
Interrupts are ____ events
Asynchronous
On an interrupt, OS preserves state of CPU by storing ____ and the ____
Registers and the Program Counter
Interrupt is processed by calling the corresponding…
…ISR (Interrupt Service Routine)
How would OS locate the correct ISR?
- An interrupt vector is stored at a known location in
memory - Each entry contains the address of an ISR
- Interrupt number is mapped to an entry in interrupt
vector
What does interrupt (or event) driven mean?
OS sits idle until something happens
