What is the order of FDE Cycle
program counter stores address of intruction to be fetched
instruction is then read by MAR which then gets a copy of the address
then using data bus, a copy of data is sent to MDR
Control unit splits up the instruction into opcode and operand code and sends to CIR
Value in PC is then incramented by 1
How does more cache affect performance?
More space for instructions and data in cache
RAM needs to be accessed less frequently
cache is faster than RAM, as inside processor
How does more cores affect performance?
more programs are able to run at the same time
How does fast clock speed affect a processors performance?
More instructions can be carried out per second
More cycles per second
less time taken to run a program
What is a procedural language?
A high level language which gives a series of instructions in a logical order
What is purpose of memory managment?
organise use of main memory
allows programs to allocate memory
protects programs from each other
What is the interrupt service routine?
Completes current FDE cycle
Checks priority of interrupt
if priority higher than current task
Remove tasks with less priority and place in temporary stak
load ISR
when complete return item from stack and place into registers
Circuit switching
direct link created between two devices which is maintained throughout conversation
DEVICES MUST TRANSFER AND RECIEVE DATA AT SAME RATE
data arrives in a logical order meaning can be reconstructred faster
there is no delay
however,
bandwith is wasted when no data is sent
ties up sections of network which cant be used until transmission done
application software vs utility software?
Application Software
designed to be used by user to complete specific task
Utility Software
designed to perform a specific task related to the upkeep / improvement of computer
open source vs closed source?
Open source
free to use by anyone, user can view source code
lower security
Closed source
user needs license, can’t access source code
higher levels of security
What tests does the BIOS run?
POST - checks all hardware is working correctly
Checks CPU clock, memory and processor
Checks external memory devices connected
how does an interpreter work?
translate and execute line by line, stops at error
slower than compiler
good for testing sections of code
can be used on a range of platforms / devices if interpreter is available
Harvard Architecture features
faster execution
different bus for for instruction and data
different physical memory for instructions and data
single clock cycle to run an instruction
can read and write whilst accessing instructions
string handling commands
stringname.length - returns length of string
string.substring(start,howmany) - produces letters in range
str() - converts to string
string.upper() / .lower - makes caps or lowercase
string.isupper() / .islower() - returns true or false
how does a compiler work?
high level code -> machine code : in one go. error sheet at end
specific to OS / processor so may need to be compiled again for different device
code can be run without a translator
longest translator
Von Neumann features
same bus for data and instructions
same physical memory for data and instructions
cheaper to design
used in PC and small computers
can’t read and write whilst accessing instructions
Why is scheduling necessary?
so as many jobs can be processed in the shortest amount of time ,
to make efficient use of recourses and have fast response times
features of contemporary processors?
uses Von Neumann when working with data and instructions
uses Harvard to divide data and instructions into separate cache
How does DNS play a role in websites being loaded?
DNS used to resolve corresponding IP to its URL
sends a request to DNS resolver
resolver checks cache if doesnt hold URL passed to TLD which checks amd returns answer or passes to ANS
IP returned to client
or error if no resolution
Why are protocols important on a network?
A set of rules
Ensures devices can communicate with each other
So they interpret data and signals the same way
TCP / IP STACK
4 Different layers (ATIL)
Application - decides which protocol will be used
Transport - checks all network data recieved
Internet - sends data to other devices using IP
Link - hardware connection between the devices
What is an array?
a data structure holding multiple pieces of data.
accessible by a single identifier
it holds data of the same type
elements are accessed by an index
What is required for run length encoding to work well?
Consecutive pieces of data being the same, or else doesn’t offer great reduction in size
list different application software
Desktop publishing
Word processing
spread sheets
web browsers
list utility softwares
antivirus
disk defragment
compression
backup
what is run length encoding?
repeated values removed and replaced with one occurrence along with how many times it should be repeated e.g.
AAAAAABBBCC
A6B32C
which searching algorithms are 0(n^2)?
bubble sort
insertion sort
faster for smaller data set
How does packet switching work?
packets deconstructed
packets sent, with header (containing info e.g. destination)
packets take different routes (most efficient)
if one route breaks can take another
packets reconstructed
can be transferred over very large networks
all packets must arrive before data recieved
takes time to deconstruct and reconstruct
Multicore cpu vs Parallel System
Multicore CPU:
many independant cores carry instructions seperately
Parallel Sysyem
Complete tasks w/ single core by using threading
What is magnetic storage, giving examples?
uses 2 states which are represented using binary
hard disk
magnetic tape
floppy disks
pros: high capacity, cost effective durable
cons: slow
what is flash storage, giving examples?
uses silicone semi conductors
e.g. SSD
pros: fast, portable
cons: cost
What is optical storage, giving examples?
uses lasers to read and write
CD
DVD
Blu-ray
pros: cheap, portable
cons: risk of loss, slow
what is the role of program counter?
stores address of next instruction to be processed
What is ASCII?
a character set which maps values to characters using 8 bits.
What is RISC?
Reduced Instruction Set Computer
small instruction set
1 instruction = 1 line
takes many lines to complete an instruction such as multiply
in what ways is the accumulator used?
temporary storage for data being processed during calculations
what is the role of the control unit?
decodes instructions
sends control signals
How to put something into 2NF?
be 1NF
no partial key dependencies (can’t depend on a secondary key)
What does ACID stand for?
Atomocity
Consistency
Isolation
Durability
What is a primary key?
A field which has a unique values for each record in that table
what is prefetching?
using algorithms to predict which instruction soon fetched. Then stored in cache.
Algorithms must be highly accurate + no guarantee it is right
How to put something into 1NF?
No repeating groups of attributes
(Attributes shouldn’t contain more than a single value)
file handling commands
file.openread(“ “) - opens file to read
file.openwrite(“ “) - opens file to write
file.readline() - reads a line
file.writeline(“ “) - writes to line
file.close()
What is dictionary coding?
Frequently occurring data replaced with index and compressed data stored in dictionary
Good for repeating groups of data
E.g.
role of an assembler?
translates low level language to machine code (one-to-one basis)
Different systems software
operating system
device drivers
What is CISC?
Complex Instruction Set Computer
large instruction set
used in micro controllers + embedded systems
1 line to multiply
RISC VS CISC
RISC creates more work for the compiler.
RISC requires more RAM to store code
RISC has pipelining available
CISC has less work, requires less RAm and only has a few special instructions
what is a register?
a piece of memory used to store data
within the processor
Methods of Memory Managment
PAGING
memory split up into equal size pages
uses virtual memory
physical divisions
SEGMENTATION
memory is divided based on program flow
logical divisions
VIRTUAL MEMORY
section of hard drive acts as RAM when not enough space.
Sections of programs currently not being used moved here to free space in RAM
PROBLEM CAN HAVE DISK THRASHING (FREEZING) DUE TO SWITCHING BETWEEN HARD DISK AND MEMORY
harvard vs von-neuman architecture?
more expensive
has different memory and bus for data and instructions
fixed memory size
buses can transmit and recieve simultaneously
mainly used in super computers
von neumann
chaper, faster to develop
takes more cycles to complete a task
same bus and memory for data and instructions
used in PC’s
what is indirect addressing?
operand gives the address of a register which holds another address, where the data is located.
what is indexed addressing?
An index register is used, which stores a value. The address of the operand is determined by adding the operand to the index register.
what is immediate addressing?
operand is the actual value.
what is direct addressing?
operand gives the address which holds the value . Direct addressing is used in LMC.
How to put something into 3NF?
Is 2NF
No non key dependencies (only depends on primary key and nothing else)
what is a parallel system?
one which contains a CPU and GPU
what is a multilevel feedback queue?
makes use of multiple queues, each ordered based on a different priority.
can be difficult to implement due to deciding which job to prioritise based on a combination of priorities.
What is intermediate code?
Half way between machine and object code - independant of processor architecture so can be used on different OS and machines
what is a proxy server?
Acts as a medium, collecting and sending data on behalf of user
what is a bridge?
links together two LANS
what is a gateway?
provides link between two dissimilar networks e.g. LAN and WAN
advantages of packet switching over circuit switching?
safer from interception due to packets using multiple routes
more efficient as routes are only tied up for short periods of time
What is the ALU?
Completes all arithmetic and logical operations.
what is a programming paradigm?
different approaches to using a programming language to solve problems.
Split into imperative and declarative
What is an imperative programming paradigm giving examples?
use code which specifies the action to be performed
e.g. procedural and object orientated such as python
what is a declarative programming paradigm?
stating desired result rather than exact series of instruction required to perform it.
E.g. functional and logical languages such as java and SQL
problem with branching and pipelining?
BRP could be followed by 2 possible instructions - only determined at execution. So wrong instruction may be fetched or decoded
What is an IP address?
A numerical address made of 4 numbers between 0 and 255
Uniquely identifies a device on a network
Atomocity?
Transaction processed in entirety or not at all
Consistency?
Transaction must maintain referential integrity
Simultaneous executions of transaction should lead to same result
Durability?
When transaction executed, it remains same regardless of circumstances
how does a search engine index a page?
uses a program called a spider which traverses the web
takes in each word from page and adds an entry under the word in the index
along with the position of the word in the page
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