4) Computer Systems Flashcards
What are computer’s hardware devices?
Primary storage
Secondary storage
I/O devices
Processors
What is secondary storage?
Memory that can store data and instructions not currently in use
What are examples of I/O devices?
Keyboard
Mouse
Monitor
Speakers
What are the main types of secondary storage?
Hard disk drive (HDD)
Solid state drive (SSD)
Compact disk (CD)
Flash (USB drive)
What are processors?
Special components that process data and instructions to control other componets
What are the 2 main types of processor?
Central processing unit (CPU)
Graphics processing unit (GPU)
What is primary storage?
The memory used to store data or instructions currently in use
What are the types of primary storage?
Random access memory (RAM)
Read-only memory (ROM)
What are general purpose systems?
Systems capable of performing many different tasks
What are examples of general purpose systems?
PCs
Macs
Smartphones
What are embedded systems?
Computer systems built into a device to support its function
What is a transistor?
An electrical component that acts as an electrically controlled switch
What do transistors do?
Temporarily store data
What is the presence of electricity represented by?
1
What are transistors arranged into?
Circuits
What can transistor circuits do?
Perform operations such as calculations
What do multiple transistors create?
Logic gates and logic circuits
What are examples of logic gates?
AND
OR
NOT
XOR
When does an AND gate output true?
If both inputs are true
When does an OR gate output true?
If either or both inputs are true
When does a NOT gate output true?
If the input is false
What functions can logic circuits perform?
Adding numbers
Storing data
What should you evaluate in an expression first?
Brackets
NOT (True OR False) –> NOT(True) –> False
What do truth tables show?
The input and output state for each combination of a logic circuit
What is the symbol for an AND operator?
-
What is the symbol for an OR operator?
+
What is the symbol for a NOT operator?
A line above the variable
What is the most common type of computer software?
Application software
What does application software help a user to do?
Complete a given task
What are examples of application software?
Presentation software
Word processors
Web browsers
What does ystem software control and provide?
Controls the hardware
Provides an environment for applications to run
What are examples of system software?
Device drivers
Operating systems (OSs)
Utility software
What are device drivers?
Small programs which tell the OS how to use a piece of hardware
What do operating systems (OSs) do?
Manage access to hardware in the computer
What does utility software do?
Performs maintenance tasks to make sure system operation continues
What are the types of utility software?
Defragmentation
Backup
Compression
Decryption
What is defragmentation?
Improving hard disk performance by applying an algorithm to reorganise data
What is backup?
Making copies of data that can be stored in the event of a data loss
What is compression?
Applying an algorithm to reduce the space needed to represent a file
What is encryption?
Applying an algorithm to ‘scramble’ data to prevent unauthorised access
What are operating systems?
Essential pieces of software that load up when a computer boots up
What is an application programming interface (API)?
A set of code libraries developers can use to write applications for that OS
What does API stand for?
Application programming interface
What are managers responsible for?
Many pieces of hardware
What are the types of manager?
User interface (UI) manager Device manager Memory manager User manager Process manager File manager
What does the user interface manager provide?
The user interface which allows users to control the computer
What does the device manager allocate?
Allocates resources to external hardware devices and allows them to be used by applications
What does the memory manager control?
The allocation of memory between applications
What does the user manager do?
Authenticates and separates users of the computer
What does the process manager do?
Controls the allocation of the CPU cycles to multiple running applications
What does the file manager control?
Opening, reading and writing of files in secondary storage
What does the user interface do?
Allow users to interact with a computer system
What does CLI stand for?
Command line interface
What is a command line interface (CLI)?
An environment where the computer is controlled by typing text commands on a keyboard
The computer cannot display graphics
What does GUI stand for?
Graphical user interface
What are graphical user interfaces (GUIs)?
A UI based on the window-icon-menu pointer model or
A multi-touch surface
What does WIMP stand for?
Window-icon-menu-pointer
What does the memory manager allocate?
RAM to each running process
What does the device manager allow and keep track of?
Which devices are connected at each port
Allows applications to read or write data
What is multiple applications running at once known as?
Multitasking
What are examples of peripheral devices?
Keyboard
Mouse
Printer
Webcam
What 3 things does the file manager control?
Access rights
Locations
File types
What are the possible file access rights?
Read
Modify
Execute
What is a single-user OS?
A OS which supports one user at a time
What is a multi-user OS?
An OS which allows several users to be connected at the same time
What does the user manager keep track of?
Which users can access the system
Who is logged in
Authentication
Decisions based on access rights
What are all modern CPUs based on?
Von Neumann Architecture
What does ALU stand for?
Arithmetic logic unit
What does the ALU do?
Performs arithmetic and logical operations of the CPU
What are examples of arithmetic and logical operations in the CPU?
Addition, Subtraction, Multiplication, Division
Comparisons
Boolean operations
What does CU stand for?
Control unit
What does the control unit do?
Sends out signals to other parts of the CPU
Executes the FDE cycle
What 2 parts is the control unit made up of?
The clock
The decoder
What does the CU clock do?
Coordinates the CPU’s activity
What does the CU decoder do?
Decodes the program instructions
What are CPU registers?
Tiny amounts of super-quick memory
Used to hold information needed for CPU to work
What does MDR stand for?
Memory data register
What does MAR stand for?
Memory address register
What does the MDR do?
Holds the data that has been or is about to be stored in memory
What does the MAR do?
Holds the address of the location in memory where data is to be retrieved or stored
What does a CPU PC stand for?
Program counter
What does the program counter do?
Holds the memory location address of the next instruction to be performed by the CPU
What does ACC stand for?
Accumulator?
What does the ACC do?
Holds the result of calculations and operations peformed by the ALU
How does a processor retrieve and process instructions and data from memory?
By following the FDE cycle
What happens in the fetch stage of the FDE cycle?
Address of next instruction copied from PC to MAR, PC incremented to point to the next intsruction, instruction stored at location held by MAR is copied to the MDR
What happens in the decode stage of the FDE cycle?
CU decodes information and sends signals to the component within or outside the CPU that needs to act
What happens in the decode stage of the FDE cycle?
Operation indicated by instruction is performed by appropriate component
e.g. ALU performs operation given by CU
What factors affect CPU performance?
Clock speed
Cache type
Core amount
What triggers the next stage of the FDE cycle?
CPU’s clock sends a pulse at fixed intervals
What does higher clock speed mean for instructions?
Higher clock speed = more pulses per second = more instructions executed in the same amount of time
What are the cache types?
Level 1
Level 2
Level 3
What are characteristics of level 1 cache?
Fastest but smallest cache
Found inside CPU
What are characteristics of level 2 cache?
Second fastest and large cache than level 1
Found on a secondary chip close to CPU
What are characteristics of level 3 cache?
Slowest but largest cache
Found on a chip between CPU and main store
What is cache?
Very small, very fast memory found inside or very close to the CPU
What is stored in cache memory?
Frequently accessed data amd instructions
Avoid accessing RAM
What does each core have?
Control unit
Arithmetic logic unit
What is each core capable of?
Processing instructions independently
What does cores share?
Access to cache and main memory
What do multiple cores allow?
The CPU to process multiple instructions at the same time
What are characteristics of RAM?
Volatile
Fast
Random access
Expensive
What does volatile mean?
Content lost when power is lost
What does random access mean?
All parts of memory can be accessed equally as quickly
What does ROM come on?
A small factory made chip on the motherboard
What type of memory is ROM often made from?
Flash memory so contents cannot be changed easily
What does ROM store?
Small programs that boot up or start up the computer
What are programs that boot up the computer called?
Basic Input Output System (BIOS)
What does BIOS stand for?
Basic Input Ouput System
What does a BIOS usually do?
Load an operating system
Check the system for errors
What are characteristics of ROM?
Read only
Non-volatile
Fast but expensive
What is solid state storage often referred to as?
Flash storage or flash memory
How reliable are solid state drives and why?
Robust
No moving parts
Not easily damaged by shocks
Limited number or read/ write cycles
What does SSD stand for?
Solid state drive
How can data be accessed on SSDs?
Random access as there is no moving parts
How do SSDs store a bit?
Flash memory stores the value of each bit in a semiconductor chip
What are properties of SSDs?
High speed
High cost
Good capacity
Good reliability
How is a bit stored on magnetic storage?
Each bit is represented as a postively or negatively charged magnetic particles
What are magnetic particles stored on?
A magnetic disk called the platter
How is data accessed on magnetic storage?
To read/ write data we need to find the location on the disk
A magnetic read/ write head is used to access data while the platter spins
How reliable is magnetic storage?
Moving parts so subject to wear-and-tear
Can be damaged by shocks
Not robust
What does HDD stand for?
Hard disk drive
What are properties of magnetic storage?
High capacity
Low cost
Low speed
Good reliability
What storage type is popular for archives and home computers?
Magnetic storage
What are examples of magnetic storage?
Hard disk drives (HDDs)
Hybrid drives
Magnetic tape
What are hybrid drives?
A combination of magnetic and SSD storage offers the benefits of both systems
What did magnetic tape used to be popular for?
Distributing content:
Audio
Video
Software
What is magnetic tape currently used for?
Making backups
How does optical storage work?
Uses laser light to retrieve data from the surface of optical media
What are the types of physical storages?
Solid state drives (SSDs)
Magnetic storage
Optical storage
What is optical storage often used to deliver?
Multimedia content such as video
What does multimedia mean?
Combining media types such as sound and image
How is a bit stored on optical storage?
A bit is represented as a microscopic hole or a flat surface on the surface of a disk
What is an optical storage hole called?
A pit
What is an optical storage flat surface called?
A land
How is data accessed on optical storage?
A lasher is shone and the disk and will be reflected to a sensor on a land and elsewhere on a pit
What are properties of optical storage?
Good reliability
Good capacity
Low cost
Low speed
What makes optical storage ideal for transportation?
Shockproof
Waterproof
What does robust storage mean?
Resistant to shocks
What are examples of optical storage?
Digital versatile disk (DVD)
Blu-ray disks (BD)
Compact disk (CD)
What does DVD stand for?
Digital versatile disk
What does CD stand for?
Compact disk
How much data can a DVD store?
4.7GB
How much data can a BD store?
25GB
What does BD stand for?
Blu-ray disk
How much data can a CD store?
700MB
What are the types of optical media standards?
Read only media
Re-writable (RW)
Write once (R)
What does the cloud refer to?
Storages, devces and applications that exist on the internet rather than local secondary storage
What is the cloud often used to store?
Files
Audio and video
Applications
Servers
What are examples of cloud applications?
Google docs
Microsoft office 365
Gmail
Where do cloud services exist?
Giant data centres around the world
Why does data centres opt for expensive storage devices?
Time taken to access the data needs to be minimised
What does RAID stand for?
Redundant Array of Inexpensive Data
What is a RAID configuration?
A techniquewhere multiple small secondary storage devices can be combined together to provide a larger device
What can a RAID configuration provide?
Error recovery
How does a RAID configuration provide error recovery?
If a drive in the RAID system fails, data is kept on the other drives which helps reocover lost data
What are pros of the cloud?
Updates
Easy access
Security
What are cons of the cloud?
Privacy
Internet connection needed
Pricing changes
