Karteikarten
8. The Operating System
Karten in diesem Stapel (84)
- 1Key Terms- OS
- System software
- Application software
- Hardware - 2What does system software do?Controls:
- Hardware
- Software - 3What are the two most common types of system software?Operating system (OS)
System start-up software - 4What is application software?Specific task
- 5What is a hardware driver?Software
Bridges OS & hardware
Made by hardware devs - 6How do hardware drivers complete their job?Conv. generic request (OS) -> specific request (driver)
- 7What is the main part of the OS used for?- Process management
- Hardware management
- Other key low-level tasks - 8What is this part of the OS called?The kernel
- 9How are system interrupts dealt with?Calling an interrupt service routine (ISR)
- 10What the name of the index that file information is stored in?File allocation table (FAT)
- 11What do file systems determine?- Error detection used
- How table is managed - 12What are Window's main file systems?- FAT32
- NTFS - 13What is Mac's main file system?- HFS Plus
- 14What is Linux's main file system?- EXT3/4
- 15What is journaling?- Fault tolerance system
- Prevents inconsistent states in case of failure - 16What file systems use journaling?- HFS Plus
- NTFS
- EXT3/4 - 17What are the two types of journaling?- Meta-journaling
- Block journaling - 18What does meta-journaling do?- Log operations before commit to drive
- If operation fails, system can check log to see what should have happened - 19What happens if a save operation fails using meta-journaling?Data may be corrupted
- 20How does block journaling save data?1. Data copied to the journal
2. Data committed to drive - 21What are the implications of this?- Data restored if lost
but
- Slower (data saved twice) - 22What is a file allocation table (FAT)?Stores:
- File locations on drive
- File meta-data - 23What is a sector?Smallest unit of storage on hard drive
- 24What is a cluster?Groups of sectors
- 25How doe the FAT store files that span more than one sector?Stores location of first sector
First sector points to other sectors
e.g.
FAT(pt.1) --> pt.2 --> pt.3 --> null - 26How does the OS manage directories?It creates a special file that represents a folder
Folders contain:
- Links to other folder files (dir struct)
- List of files in folder
- Permissions and meta-data - 27What is utility software?Software for common tasks
(usually comes with OS) - 28What does file management utility software do?- Move files
- Copy files
- Rename files
- List directory content
CANNOT OPEN FILES - 29What does compression software do?- Reduces file size
- Lossless - 30What do task managers do?Allows viewing of current processes
Useful for:
- Finding bottlenecks
- Killing unresponsive programs - 31What is the purpose of anti-virus software?To protect the user against viruses:
- Scans every file, comparing them to virus database
- Monitors suspicious activity - 32A Level Start*****
- 33What is batch processing?Performing many similar tasks w/o user input
- 34What are the properties of batch processing?- Performs large # of similar jobs
- Runs without user intervention
- Runs during out-of-office hours
- Works through jobs sequentially - 35How do batch processes deal with the large volume of data?Using master and transaction files
- 36What are the different types of OSs?Single-user OS
Multi-user OS
Real-time OS - 37What are the properties of a single-user OS?- Only one user has access to system resources at once
- Each user has separate home directory - 38What are the properties of a multi-user OS?- More powerful computer
- More than one user has access to system resource at once
- Each user has a remote display
- Uses multi-tasking - 39What is multi-tasking?- Swapping apps in and out of CPU
- Gives illusion of apps running in parallel - 40What is multi-programming?Storing > 1 job in the CPU at once
Done by swapping apps to prevent the CPU becoming idle; scheduling - 41What are the properties of real-time OS?- Very fast
- Only for specific systems (e.g. power stations, aircrafts) - 42What is an interrupt?A signal sent from hardware to the CPU
- 43What handles an interrupt?The OS
- 44How is an interrupt handled?- The interrupt is sent to the CPU
- The CPU informs the OS
- The OS either ignores the interrupt or runs an interrupt service routine - 45What is an interrupt service routine (ISR)?Special code that is run in the response to an interrupt
- 46What is a buffer?Small block of memory inside of hardware
Stores work currently being handled by the device - 47When is a buffer used?When the OS isn't ready to deal with interrupts
Key presses are stored until interrupt can be handled - 48What happens if a buffer overflows?The motherboard sounds a beep
- 49What is the hard drive's buffer used for?Receiving data from CPU to be stored
- Speeds up CPU
Receiving is called spooling - 50What happens during double bufferingUses two buffers
- One buffer accepts data
- Other processes data
Once finished, 1st buffer is copied to the 2nd buffer - 51What happens during ping-pong bufferingA version of double buffering
- No swapping
- Roles are reversed after every write - 52What must a memory manager do?- Allocate enough memory to each program
- Split memory between processes
- Stop processes accessing each other's data
- Extend memory with virtual memory - 53What is stored in RAM?- The OS
- Running programs
- Current files and data - 54What is paging?Allocating blocks of memory to processes
Blocks are called pages - 55How are pages referenced?Through a paging table
- 56How are processes kept separate?Each process has its own virtual address space
This is translated by the memory unit - 57What is the formula for translating virtual memory addresses to physical addresses?Address = page number * page size + offset
- 58What is segmentation?Allows data to be split up into variably sized blocks
- 59What is stored in a segmentation table?- ID
- Start address
- Length - 60What are segments commonly used to store?- Library software
- Other shared blocks of data - 61What is virtual memoryWhen the hard drive is used as additional memory
- 62What happens to a process that is put into virtual memory?It gets suspended
- 63What happens when a process is loaded from virtual memoryIt resumes processing
- 64What records if a process is in physical or virtual memory?Page table
- 65What are the three states that a process can be in?- Running
- Blocked
- Ready to run - 66What does it mean for a process to be running?It currently has CPU time
- 67What does it mean for a process to be blocked?The program is currently waiting for an interrupt ∴ it doesn't have CPU time
- 68What does it mean for a process to be ready to run?The process is waiting for CPU time
- 69How are processes swapped out of the CPU?A process control block (PCB) is created which stores:
- The PC contents
- The general-purpose registers
- The ACC contents
- Variables and state of the process
- Priority and the process ID - 70Where are software interrupts stored?The interrupt register
- 71How are software interrupts stored?Changing the bit that refers to the interrupt from 0 to 1
- 72What happens it two of the same interrupt occur?Only the first is recorded
- 73When are interrupts handled?At the end of the FED cycle
- 74How does the system decide which interrupts to deal with?Compares the priority of both the interrupt and the current process
If interrupt > process, the ISR runs - 75How does the CPU know what ISR to run?It uses an indexed addressing mode:
interrupt handling code = base address + (index * 4) - 76Stacks and processing interrupts*TO ADD PICTURE*
- 77What is time-slicing?Used in multi-user OSs
Gives each user a set amount of CPU time - 78What is polling?Asking a device for its status
- 79What happens to a device during polling?It blocks (synchronous)
- 80What is busy-wait polling?Where the device waits (does nothing) while polling
- 81What is the alternative to this?The device continues activity and polls at regular intervals
More efficient but not as much as using interrupts - 82What is threading?Where a process splits up into parts, utilizing multiple CPU cores
- 83What are the advantages of threading?Processes don't need to block when waiting for an interrupt - they only stop using one core
- 84What is the main disadvantage of threading?There is no control over the order that threads execute in
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- A Level Computer Science ((AS) Unit 1: Fundamentals of Computer Science ) Karteikarten am 8. The Operating System, erstellt von Scott Jones am 31/07/2019.
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