for finals Flashcards
What are the functions of computers?
- Data processing
- wide data variety that requires a broader processing - Data storage - long & short term
- Data movement
-I/O = data to/from peripherals connection
- data communication = data from long distance via remote devices. - control - control unit manages computer’s resources & response to instructions
What is the function of Control Unit?
- controls CPU/ computer operation
- response to/ execute instructions
What is the function of ALU?
Performs data processing functions.
What are the structural components of the computer?
- CPU - controls computer operation & performs data processing
- I/O - data transfer between computers and external devices
- Main memory - to store data
- System Interconnection - provides communication of data between computer components
What is direct access?
- involves a shared read & write mechanism
- individual blocks has unique address based on physical location
What is sequential access?
- memory is an organized data unit called records
- accessed is in a specific linear sequence
What is random access
- each memory address has a unique addressing mechanism
- location is randomly selected & directly accessed.
What is memory hierarchy?
- separates computer memory in hierarchy based on response time
- lower access time, higher cost per bits
- greater capacities, lower cost per bits & greater access time
What are the types of addressing modes?
- immediate
- Direct & indirect
- Register
- Register indirect
- Displacement
- Stack
What is immediate addressing mode?
- data is presented in instruction address
What is direct & indirect addressing mode?
- direct = operand’s offset is in the instruction as 8-bit/16-bit displacement element
-indirect = contains the effective address of memory location where the actual data consists.
What is register & register indirect addressing mode?
- register = operands contained in a register set
register indirect = addressing operands are placed in one of the registers eg, BI,BX,SI,DI
What is displacement (auto indexed) addressing mode?
- effective address of operands in register content
- increment = register content is increment after accessing operands
- decrement = register content is decrement before accessing operands
What is stack addressing mode?
- operands at the top of the stack
What is EPROM?
- erasing process = repeatedly (UV)
- cost = expensive than PROM
- update capabilities = multiple
What is EEPROM?
- erasing process = electrically
- cost = most expensive than EPROM
- write operation = written without erasing prior contents
What is Flash Memory?
- functionalities = between EPROM & EEPROM
- cost = between EPROM & EEPROM
- erasing process = single action due to organized microchips.
What is RAID & how many levels are there?
- Redundant Assembly of Independent Disk
- level 0 -6 (7)
What is RAID 0?
- no redundancy
- 2 requirements of high transfer rate
1. high transfer capacities = stays on the path between host device & disk drive
2. I/O request = application to drive disk array effectively - I/O request is the I/O time dominated by seek & latency time
What is RAID 1?
- redundancy via mirroring
- data striping by mapping all the data to 2 separate physical disk with 1 being the mirror disk
- no write penalty
- costly due to double storage
What is RAID 2?
- redundancy via Hamming code
- parallel access
- synchronization of spindles & same head position
- data striping can be as small as a word or byte
- Hamming error correcting code to correct single-bit error & detect double-bit error
What is RAID 3?
- redundancy via bit-interleaved parity
- like RAID 2, synchronization of spindles & same head position
- parallel access, all disks are access at once
- data striping into bits and stored into parity disk
- reduced mode is required to be reconstructed for data retrieval
What is RAID 4?
-redundancy via block-level parity
- independent access, each disk operates independently
- calculate new parity needs to read old user strip & old parity strip
- write penalty = new write requires array management software to update both user strip with the corresponding parity bits
What is RAID 5?
-redundancy via block-level distributed parity
- organized similar to RAID 4
- parity strips are distributed across all disk
- allocation is round-robin scheme
- takes 2 disks fail for data loss
What is RAID 6?
- redundancy via dual-redundancy
- 2 different parity strips are stored on 2 different disks & blocks
- high data availability & recover
- takes 3 disks for data loss
- substantial write penalty, 2 parity disk affected.
What are the types of I/O commands?
- Control = activate peripherals & tells what to do
- Test = test status condition associated with I/O modules & peripherals
- Read = I/O module obtain data from peripheral & place it in internal buffer
- Write = I/o module obtain data from data bus & transmit to peripheral
What are the key interface of OS?
- Instruction Set Architecture (ISA)
- Application Binary Interface (ABI)
- Application Program Interface (API)
What is ISA?
- boundary between software & hardware
- allows software to control CPU via machine language
What is ABI?
- in between OS and application in the context of binary codes
- defines the system call interface to the OS & hardware resources & services of the system via user ISA
What is API?
- gives programs access to hardware resources
- application software to be ported easily to other system with the same API
What are the services provided by the OS?
- Program creation & execution
- access I/O devices
- Error detection & responses
- Accounting
- System access
What are the scheduling of multiprogramming?
- Long-term = Add into the pool of processes to be executed
- Medium-term = Add a number of processes either partially/fully into the main memory (swapping in & out)
- Short-term = available processes will be executed by the processor
= makes fine-grained decision on what to execute next
What is I/O scheduling?
- any pending I/O request can be handled by any available I/O device
What is Virtual memory demanding paging?
- each page of a process is brought in when needed
- principle of locality
1. subroutine = large process execution may be confined in a small section of a program
- page fault = if page is not within main memory, OS will fetch the desired page
pros 1. more processes maintain in memory
2. time saving by swapping in & out
cons
1. page replacement (1 page in1 page out)
2. OS has to fetch page again before the page used is thrown out
What is Virtual Memory Address Translation?
- Supersections = 16Mb blocks of MM
- Sections = 1Mb blocks of MM
- Large pages = 64kb blocks of MM
- Small pages = 4kb blocks of MM
Lvl 1 table
- holds descriptors containing base address & translation properties for Supersections & Sections
- pointers to lvl 2 tables
Lvl 2 table
- holds descriptors containing base address & translation properties for Large & Small pages
