2023 Paper Flashcards
Cons of using closed source software for business
- no access to source code
- cannot modify/improve source code to meet business needs
- cannot fix bugs
- usually cost to purchase licences (ongoing fees)
Pros of virtual storage for backup
- no physical space needed for backup software
- no on site maintenance needed
- all data can be backed up at the same time
- can be accessed from anywhere/other machines
- stored remotely, so in case of breach (locally), data is not damaged
Pros of LAN
- share hardware
- share files
- share internet connection
- centralised security
- central maintenance
- central backup/storage
- can monitor user activity
- can control access level (centralised user admin)
Protocol
- A set of rules/agreement
- used to govern transmission/communication between devices
Why is protocol layering used?
- breaks down tasks into manageable units
- each layer is well defined (does a specific job)
- To provide independence of layers (layers can be modified without affecting other layers)
- Hardware/software can be manufactured to fit into one specific layer
- Allows for standards for individual layers to be developed (for compatibility)
Types of OS
- Multi-tasking –> runs multiple programs at the same time
- multi-user –> allows multiple users at the same time
- distributed –> allows multiple computers to work together on a single task
- embedded –> runs on dedicated hardware (dedicated function) & is read-only
- real-time –> guaranteed to execute within a known time frame
How does OS deal with an interrupt?
- interrupt checked for at start/end of FDE cycle
- if interrupt of lower/equal priority of current program, current process continues
- if interrupt raised, contents of registers are copied to stack (pushed onto the stack in a stack frame)
- PC changed to point to ISR
- After interrupt is complete, (stack frame is popped off stack) previous register values are loaded back into the registers/restored
Stack vs Queue
- Stack if LIFO, Queue is FIFO data structure
- Stack uses one pointer, Queue uses 2 pointers
- Stack, data is popped/pushed from stack, Queue, data is dequeued from start and enqueued from back
Array vs List
- Array is static (of fixed size), List is dynamic (no defined size)
- Array holds data of single data type, List can hold data of multiple types
Tuple
Tuple is immutable (cannot be changed at runtime)
how is second item accessed in linked list?
- go to first position indicated by the start pointer
- from the first position, read the next pointer value
- follow this pointer value and access the data item
Pro of storing numbers using 2’s complement rather than S&M
- Calculations are more easily performed on two’s complement
- Two’s complement allows for a larger range of numbers to be stored
- No additional hardware is required in two’s complement
Increasing mantissa increases …
accuracy of number being stored
increasing exponent increases …
range of number being stored
Assembly vs HLL
Assembly
- use mnemonics
- uses assembler to convert to machine code
- one-2-one conversion to machine code
- allows direct control of the processor
- specific to the processor being used (machine dependent)
HLL
- uses English-like words
- uses a translator to convert to machine code
- produces multiple lines of machine code per line of code (one-2-many)
- provides more abstraction
- machine independent (used for multiple processor types)
pro of multi-core processor
- can execute multiple instructions/FDE cycles at the same time
- some instructions in program can be run in parallel
cons of multi-core processor
- some instructions may not be able to run in parallel
- program needs to be specifically written to use multiple cores
- an instructions may be waiting for another instruction to be completed
encryption
- converts data into data that cannot be understood (ciphertext) using a key
- symmetric encryption uses the same key for encryption and decryption
- asymmetric encryption uses 2 keys, one for encryption and one for decryption
- encryption is 2 way, so data can be restored to original form, provided there is a key
- symmetric useful for internal data storage (no transmission)
- asymmetric useful for data transmission as data intercepted cannot be decrypted without key
hashing
- one-way (irreversible) mathematical process that produces a value from the input value
- useful for information that needs to be verified (e.g. passwords) but does not need to be known once hashed
- hash input compared against hash stored, protecting security of data from breaches
How to use copyrighted image
- buy a licence to use image/stuff
- use images marked as copyright free
- ask permission from the owner
1 NF
- each attribute name is unique (field names)
- no repeated attributes
- all data in attributes must be atomic (values in fields)
- primary key is identified
atomic
means cannot be split up further
open and write to a file
val = int(input(“Enter a value: “)
return= doCheck(val)
file = openWrite(“storedvalues.txt)
file.writeLine(val)
file.writeLine(return)
file.close()
