paper 1 - section 1 Flashcards
What is the purpose of a computer?
to take in data, process it, and then output it
What is hardware?
the physical components of the computer system, like the CPU, motherboard, monitor and printer
what is software?
the programs or applications that a computer system runs e.g. an operating system, a word processor or video game
What are embedded systems?
computer systems with a dedicated function within a larger mechanical or electrical system
What is a cpu?
A CPU (Central Processing Unit) is the “brain” of the computer system - it processes all of the data and instructions that make the system work
what are the three main parts of the CPU?
The control unit (CU), the arithmetic logic unit (ALU), and the cache.
What does the control unit do? what’s its main job?
It controls the flow of data inside and outside the CPU. It’s main job is to execute program instructions by following the fetch-decode-execute cycle.
What does the arithmetic logic unit (ALU) do?
All the calculations - it completes simple addition and subtraction, compares the size of numbers and can do multiplications and divisions using repeated addition and subtraction. It also performs logic operations such as AND, OR and NOT, and completes binary shifts.
It also contains the accumulator register.
What is the cache?
Very fast memory in the CPU - it stores regularly used data so that the CPU can access it quickly the next time it’s needed. When the CPU requests data. it checks the cache first to see if the data is there. if not, it will fetch it from RAM
What does the program counter (PC) do?
It holds the memory address of the instruction for each cycle.
What does the memory address register (MAR) do?
it holds any memory address about to be used by the CPU. the address might point to data or a CPU instruction.
what does the memory data register (MDR) do?
it holds the actual data or instruction. this may have been fetched from memory, or be waiting to be written to memory
what does the accumulator do?
stores the results of the calculations in the ALU
What happens in the “fetch” part of the fetch-decode-execute cycle?
1) The memory address is copied from the program counter to the MAR
2) The instruction stored in the MAR address is copied to the MDR
3) the program counter is incremented (increased) to point to the address of the next instruction, ready for the next cycle
What happens in the “decode” part of the fetch-decode-execute cycle?
The instruction in the MDR is decoded by the CU. The CU may then prepare for the next step, e.g. by loading values into the MAR or MDR
what happens in the “execute” part of the fetch-decode-execute cycle?
The instruction is performed. This could be: load data from memory, write data to memory, do a calculation or logic operation (using the ALU), change the address in the PC, or halt the program.
name five hardware components of a typical desktop computer.
any five from:
- power supply
- case cooling fan
- CPU
- Heat sink
- Optical drive
- RAM
- hard disk drive/HDD
- graphics card/GPU
- Motherboard
What is RAM?
High speed, volatile memory - it’s where all data, files and programs are stored while they’re being used
what is virtual memory?
a part of secondary storage that is used as extra RAM
CPU performance depends on what three factors?
Clock speed, number of cores, and cache size
what is clock speed?
The number of instructions a single processor core can carry out per second (Hz). The higher the clock speed, the greater the number of instructions that can be carried out.
How does the number of cores affect the performance of a CPU?
Each core can process data independently of the rest, so the more cores a CPU has, the more instructions it can carry out at once, so the faster it can process a batch of data
What is the cache and how does its size affect the performance of a CPU?
The cache is data storage inside the CPU that’s much faster than RAM. A larger cache gives the CPU faster access to more data it needs to process
Why can too little RAM cause a computer to run slowly?
The less RAM there is, the more the computer has to use virtual memory, which is much slower than RAM.
The more RAM a computer has, the more applications or more memory-intensive applications it can smoothly run, making it faster overall
what is a GPU?
GPUs (Graphics Processing Units) are specialised circuits for handling graphics and image processing. They relieve the processing load on the CPU, freeing it to do other things
what is primary storage? (main memory areas)
the main memory areas that the CPU can access very quickly, such as CPU registers, cache, ROM and RAM. Primary storage has the fastest read/write speeds and is mostly volatile
what is secondary storage? is it faster or slower than primary storage?
non-volatile memory that stores all data that’s not in use. Read/write speeds are much slower than primary storage.
How does a hard disk drive (HDD)/magnetic hard disk work?
A hard disk drive is made up of a stack of magnetised metal disks spinning at a rate of between 5400 and 15000 revolutions per minute. Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disks.
What are the advantages of Magnetic Hard Disks/HDDs compared to SSDs?
- They are cheaper
- They are very high-capacity
- They have a longer read/write life than SSDs
What are the negatives of magnetic hard disks/HDDs?
They aren’t very durable and are easily broken because of their moving parts. They also aren’t very portable, and can not be carried around easily
What are solid state drives (SSDs)?
storage devices with no moving parts. Most of them use a type of flash memory. They are used for the same purpose as HDDs - for internal storage
What is flash memory?
a very common type of non-volatile memory that stores data in electrical circuits by trapping electrons
which have a faster read/write time - HDDs or SSDs?
SSDs
What are the advantages of SSDs?
- They are faster than HDDs
- They don’t need defragmenting
- They are more shock-proof than HDDs
- They are silent
- They have quite a high capacity
How much data can CDs hold?
around 700 MB
How much data can DVDs hold?
around 4.7GB
How much data can Blu-Ray disks hold?
around 25 GB
what are the three forms that optical disks come in?
read only, write-once, rewritable
What are some advantages of optical disks?
- They’re very cheap (per GB)
- They’re portable
- They won’t be damaged by water or shocks (although they are easily scratched)
Put these types of storage in order of their average read/write speed:
Magnetic tape, HDD, Memory card, Optical disk, SSD
Optical disk, Memory card, magnetic tape, HDD, SSD
Put these types of storage in order of their average cost per GB:
SSD, Optical disc, HDD, Memory Card, Magnetic tape
Magnetic tape, Optical disk, HDD, memory card, SSD
Put these types of storage in order of their average capacity:
HDD, SSD, Magnetic Tape, Optical disk, Memory card
Optical disk, memory card, SSD, HDD, Magnetic Tape
What are the main functions of an operating system (OS)?
- communicate with internal and external hardware via the device drivers
- provide a user interface, allowing a user to interact with the computer
- provide a platform for different applications to run
- allow the computer to multi-task by controlling memory resources and the CPU
- deal with file management and disk management
- manage the security of the system
What is the purpose of device drivers?
device drivers allow the OS and hardware to communicate
which pieces of hardware connected to the computer system need a device driver?
all of them
What is a user interface?
A user interface allows the user to interact with a computer system - it controls what appears on the screen and how you use the computer
what is the most common type of user interface?
Graphical user interfaces (GUIs)
what are the main functions of an operating system?
- to communicate with internal and external hardware via the device drivers
- to provide a user interface, allowing a user to interact with the computer
- to provide a platform for different applications to run
- to allow the computer to multi-task by controlling memory resources and the CPU
- to deal with file management and disk management
to manage the security of the system
what do device drivers do?
device drivers allow the OS and the hardware to communicate with each other - they essentially act as ‘translator’ for the signals between OS and harware
what is the purpose of a user interface?
it allows the user to interact with a computer system
what is the most common type of user interface?
Graphical User Interface (GUI) - they’re designed to be easy for everyday users by making them visual, interactive and intuitive
what is a WIMP-based GUI?
a GUI using Windows, Icons, Menus and Pointers
are Android and IOS WIMP-based?
no - they were created for touch-screen devices, using finger gestures like pinching and swiping in place of a mouse
what is a command-line interface?
a command-line interface is text based. The user enters specific commands to complete tasks. Command-line interfaces are less resource-heavy than GUIs
pros and cons of command-line interfaces
command-line interfaces aren’t suitable for everyday users. But for advanced users, they can be far more efficient and powerful than a GUI. They can be used to automate processes using scripts (simple programs)
how do operating systems provide a platform to run applications?
by configuring hardware so they can use it and giving access to the CPU and memory
how does the OS help the CPU carry out multitasking?
by efficiently managing memory and CPU processing time:
- when an application is opened, the OS moves the necessary parts to memory, followed by additional parts when they are required. The OS will decide if the applications or features have been used recently: if not, they may be removed from memory
- To run multiple applications, the OS needs to make sure that the applications don’t overwrite or interfere with each other. A memory manager allocates certain applications certain memory addresses, to make sure their processes are placed into separate locations
- only one application is processed by the CPU at a time, so the other processes must wait. the OS divides CPU time between open applications and may prioritise certain processes in order for instructions to be executed in the most efficient order
- when required, the OS organises the movement of data to and from virtual memory
what handles file and disk management?
the operating system
what is file management?
the organisation of data into a usable hierarchical structure
how is the hard disk managed by the operating system?
the operating system splits the physical disk into storage sectors, decides which sectors to write data to, and keeps track of free space on the disk. Ideally, the data for a single file would be placed in adjacent sectors, but this isn’t always possible
what can file compression software do?
reduce the size of individual files
what is encryption software used for?
securing the contents of files
what can defragmentation software help to do?
organise and maintain the hard disk by collecting all the free space together
what are single-user operating systems?
single user operating systems allow only one user to use the computer at once. Most common OSs, such as Windows 10 and OS X, are single-user operating systems, even if the computer has multiple user accounts, or is connected to a network
what are multi-user operating systems?
Multi-user OSs (e.g. UNIX server) allow several users to use the computer at the same time. They’re often used on mainframes (huge supercomputers) and give many users simultaneous access. For example, ATMs allow thousands of people access to a large bank’s mainframe at the same time
what is responsible for user account control?
the operating system
what is responsible for file management?
the operating system
what is the hard disk managed by?
the operating system
what does utility system software help to do?
maintain or configure a computer
what do defragmentation utilities do?
put broken up files back together - defragmentation software reorganises data on the hard drive to put fragmented files back together. It also moves files to collect all the free space together, which helps to prevent further fragmentation
how do files become fragmented?
Files are stored on a hard disk in available spaces. Ideally, entire files would all be stored together. However, as files are moved, deleted and change size, lots of small gaps begin to appear on the disk. Over time, the disk becomes more and more fragmented.
why is reading and writing fragmented files slower?
the read/write head has to move back and forth across the disk
is defragmentation used on SSDs? Why?
As SSDs use flash storage with no moving parts, fragmentation doesn’t cause them any problems - they can access data just as quickly however it’s arranged. In fact, as SSDs have a limited number of read/writes, defragmenting them can actually shorten their lifespan
what do backup utilities help to do?
backup data
what is a backup?
a backup is a copy of a computer system’s files and settings stored externally. this means data can be recovered in the event of data loss
what are some reasons data might be lost?
fire, theft, flood, malware, hardware failure, accidentally deleting a file
what is a backup utility?
software with facilities such as scheduling of regular backups, creating rescue disks, disk images, and options for full or incremental backups
what is a full backup?
a copy is taken of every file on the system. They often use a lot of storage space. A full backup can take a long time to create, but it’s faster to restore from
what are incremental backups? What are the advantages and disadvantages of them?
only the files created or edited since the last backup are copied. They use less storage space and are much quicker to create. But, a full system restore is slow - the last full backup must be restored, followed by every incremental backup since that point
what does compression software do? where is it often used and why?
compression software reduces the size of files so they take up less disk space. it’s used lots on the internet to make files quicker to download.
what are standard file formats for compressed files?
.zip and .rar
what do you need to do to compressed files before you can use them?
extract them
what does encryption software do?
encryption software scrambles (encrypts) data to stop third-parties from accessing it. Encrypted data can be decrypted using a special ‘key’
what is open source software?
software where the source code is made freely available. Users may legally modify the source code to create their own spin-off software, which can be shared under the same licence and terms as the the original software. open source software is usually free.
what are some examples of open source software
Linux, Apache HTTP server (runs web servers), GIMP (image editing), Mozilla Firefox (web browser), and VLC media player
name 5 advantages of open-source software
- it is (usually) free
- made for the greater good, not for profit - it benefits everyone, encourages collaboration, sharing of ideas
- software can be adapted by users to fit their needs
- wide pool of collaborators can be more creative and innovative than the programmers of one company
- popular software is very reliable and secure - any problems are quickly solved by the community
name 5 disadvantages of open-source software
- small projects may not get regular updates, and so could be buggy or have unpatched security holes
- there may be limited user documentation
- no warranties if something goes wrong
- no customer support (although community forums will often make up for this)
- companies using open-source code to make custom software may not want competitors to see their source code, but they have no choice
what is proprietary software?
software, usually paid for, where only the compiled code is released. The source code is usually a closely-guarded secret.
what do proprietary software licenses restrict?
the modification, copying and redistribution of the software
what is compiled code?
the final file (e.g. the .exe file) that runs - it doesn’t tell you how the program was made
do microsoft and adobe produce open-source or proprietary software?
proprietary
what are some examples of proprietary software?
Microsoft Office, Windows, Outlook, Adobe Photoshop
what are three advantages of proprietary software?
- comes with warranties, documentation and customer support
- should be well-tested and reliable as the company’s reputation depends on this. Fixes and updates will come regularly (open source will vary more)
- usually cheaper for companies than developing their own custom-built software
3.
what are 3 disadvantages of proprietary software?
- it can be expensive
- software may not exactly fit a user’s needs, and they can’t do anything about it
- software companies may not maintain older software after warranties expire - they’ll want people to buy their latest product
give one way in which an operating system can help to secure a users data
one from:
- user account control
- password/pin protection
- pattern locking
- fingerprint/retina scanning
what does URL stand for?
uniform resource locators
