COMPUTER SCIENCE OCR “MARK-SCHEME PERFECT” MIXED NOTES
note: this doesn’t include everything in the spec, these were just, for me, what i needed to
recall to ensure i got the marks for some parts of the content
PAPER 1
● non-graphical use of a GPU: performing complex numerical calculations e.g.
insurance pricing (context)
● pipelining: concurrent processing of multiple instructions
○ one instruction can be fetched whilst prev is being decoded and prev is being
executed
○ in case of a branch pipeline is flushed
○ increases speed of execution
● IP address: a numerical address made up of 4 numbers each between 0 and 255 that
uniquely identifies a device on a network
● foreign key: an attribute that links two tables together to create relationships
between them
● magnetic storage: devices include magnetic hard drives + magnetic tape
○ data stored by altering magnetic field of a small section of the tape/disk
■ one orientation represents binary value of 1 and opposite represents 0
○ uses moving magnetic parts (read and write heads)
○ written to using a red head which reads magnetic fields to retrieve data
○ suitable for storing OS, software and data
○ large capacity
○ cheap purchasing price and reliability -- ideal for heavy use in insurance
offices
● solid state storage: drives can be based on NAND flash or DRAM
○ data stored using semiconductors
○ no moving parts required
○ backup involves copying potentially large amounts of data to and from
devices at regular intervals
○ servers distribute data to client devices
● describe the LMC mnemonic
○ BRP - branch if positive or zero
○ STA - store value in accumulator at address given
○ LDA + OUT - outputs a value held in memory
● benefit of memory management
○ multitasking -- allows multiple programs to run at once
● (currently unneeded) pages moved from memory to secondary storage when RAM
is full to create room in memory
● a device driver is a program
● examples of utility software + purpose
○ encryption…scrambles meaning of data files with a key
○ defragmentation…organises file segments on secondary storage
○ compression… reduces size of files
, ○ backup…makes regular copies of files in case of loss
● using an open source IDE is likely to be free of cost
● library:
○ pre-written, pre-tested sections of code which contain useful routines
○ e.g. encryption
○ can significantly increase size of compiled file as it contains many unused
subroutines
○ libraries need to be linked because the user may not have it installed onto
their machine -- the relevant code needs to be included in the final executable
code -- it is the job of the linker to combine this code
● linker:
○ used to link main program to external libraries
○ can either be included in the final executable code, or get the code to point to
the external libraries
● primary key:
○ a field which has a unique value for every record in a database
● hash:
○ a result generated by applying an algorithm to a value
○ advantage
■ hash functions are one way - if someone gains access to the database
they cannot access the user’s password
● purpose of a GPU:
○ to run CAD software
○ to render models of ‘x’
○ run modelling calculations
● why use an OS which is capable of multitasking:
○ to ensure more than one program can be run concurrently
○ e.g. running CAD software whilst checking emails
● firewall: a piece of software which monitors traffic going to and from a network
● linked list: a dynamic data structure which consists of nodes - these nodes contain
data + pointer. the pointer gives the location of the next node.
● linked list vs hash table:
○ HT
■ enables direct access to location of records
■ as more nodes are added, it will take the same amount of time to
search
○ LL
■ requires every node to be checked when searched
■ as more nodes are added, it will take longer to search
● why use lossless compression:
○ original data not lost whilst information lost in lossy
○ with text, loss of small amounts of info will make it unreadable
● DRM: encrypted data until a certain date
● state an instruction which changes the value in the PC:
○ BRP, BRZ, BRA
● in SQL, it is “=” not “==”
note: this doesn’t include everything in the spec, these were just, for me, what i needed to
recall to ensure i got the marks for some parts of the content
PAPER 1
● non-graphical use of a GPU: performing complex numerical calculations e.g.
insurance pricing (context)
● pipelining: concurrent processing of multiple instructions
○ one instruction can be fetched whilst prev is being decoded and prev is being
executed
○ in case of a branch pipeline is flushed
○ increases speed of execution
● IP address: a numerical address made up of 4 numbers each between 0 and 255 that
uniquely identifies a device on a network
● foreign key: an attribute that links two tables together to create relationships
between them
● magnetic storage: devices include magnetic hard drives + magnetic tape
○ data stored by altering magnetic field of a small section of the tape/disk
■ one orientation represents binary value of 1 and opposite represents 0
○ uses moving magnetic parts (read and write heads)
○ written to using a red head which reads magnetic fields to retrieve data
○ suitable for storing OS, software and data
○ large capacity
○ cheap purchasing price and reliability -- ideal for heavy use in insurance
offices
● solid state storage: drives can be based on NAND flash or DRAM
○ data stored using semiconductors
○ no moving parts required
○ backup involves copying potentially large amounts of data to and from
devices at regular intervals
○ servers distribute data to client devices
● describe the LMC mnemonic
○ BRP - branch if positive or zero
○ STA - store value in accumulator at address given
○ LDA + OUT - outputs a value held in memory
● benefit of memory management
○ multitasking -- allows multiple programs to run at once
● (currently unneeded) pages moved from memory to secondary storage when RAM
is full to create room in memory
● a device driver is a program
● examples of utility software + purpose
○ encryption…scrambles meaning of data files with a key
○ defragmentation…organises file segments on secondary storage
○ compression… reduces size of files
, ○ backup…makes regular copies of files in case of loss
● using an open source IDE is likely to be free of cost
● library:
○ pre-written, pre-tested sections of code which contain useful routines
○ e.g. encryption
○ can significantly increase size of compiled file as it contains many unused
subroutines
○ libraries need to be linked because the user may not have it installed onto
their machine -- the relevant code needs to be included in the final executable
code -- it is the job of the linker to combine this code
● linker:
○ used to link main program to external libraries
○ can either be included in the final executable code, or get the code to point to
the external libraries
● primary key:
○ a field which has a unique value for every record in a database
● hash:
○ a result generated by applying an algorithm to a value
○ advantage
■ hash functions are one way - if someone gains access to the database
they cannot access the user’s password
● purpose of a GPU:
○ to run CAD software
○ to render models of ‘x’
○ run modelling calculations
● why use an OS which is capable of multitasking:
○ to ensure more than one program can be run concurrently
○ e.g. running CAD software whilst checking emails
● firewall: a piece of software which monitors traffic going to and from a network
● linked list: a dynamic data structure which consists of nodes - these nodes contain
data + pointer. the pointer gives the location of the next node.
● linked list vs hash table:
○ HT
■ enables direct access to location of records
■ as more nodes are added, it will take the same amount of time to
search
○ LL
■ requires every node to be checked when searched
■ as more nodes are added, it will take longer to search
● why use lossless compression:
○ original data not lost whilst information lost in lossy
○ with text, loss of small amounts of info will make it unreadable
● DRM: encrypted data until a certain date
● state an instruction which changes the value in the PC:
○ BRP, BRZ, BRA
● in SQL, it is “=” not “==”
