8525 Unit 4 Flashcards
Examples of hardware
Input devices:
Keyboard
Mouse
Trackpad
Microphone
Output devices:
Display
printer
Speakers
Storage devices:
Hard drive
CD/DVD/Blu-ray drive
SD cards
Flash media
Definition of hardware
Hardware are the physical components that make up a computer system, including input/output/storage devices, the CPU and RAM
Examples of software
Offic suite
Operating system
Computer games
Web browser
Email client
Photo editing software
Software definition
The non physical programs that are stored by and run on a computer system
Software makes use of physical hardware components and devices as the way of:
- taking inputs from users
- outputting information to users
- storing information
System software
The software that provides a platform for other software to work, including OS and utility programs
Operating system examples
Microsoft
Google
Apple
What does an operating system do
MANAGE computer hardware, users and the resources used by software
Responsible for MANAGING:
Processors
Memory
Input/output devices
Applications
Security
What does an operating system do: processors
Programs are run by one or more processors
A single processor can have a number of cores
Each core is essentially another processor
The operating system is responsible for deciding which program will run on the processor and how much time it will get to run
What does an operating system do: memory management
To run a program, the computer must copy the program from storage into main memory
The operating system keeps a record of where each program and its data are located and will make sure not to overwrite existing data
What does an operating system do: input/output devices
OS manages getting inputs from and sending outputs to peripheral devices (mice, keyboard, printers, displays, digital cameras, graphics tablets)
What does an operating system do: device drivers
Device driver is a program that controls peripheral devices
Each device uses its driver to communicate with the OS
What does an operating system do: sending data to a printer
Computer sends data to printer
Data is sent to a print queue
Data in print queue is transmitted to the printer
Printer will send its status back to OS, e.g out of paper (hardware interrupt)
What does an operating system do: application management
E.g web browsers, music and video players, PDF viewers, email clients and instant messaging software
The OS provides graphical user interface—windows, minimise, maximise, resize
OS copies the program into RAM and allocates an area of the RAM for the program to use when a new application is opened
Likewise the OS makes sure that the application’s program is removed from the RAM when it is closed
OS responsible for install and updating applications
What does an operating system do: security management
User management—sorts all users and their passwords in a file/database
Access rights to files, programs and services:
computer used by more than one person—each user only allowed to see their own files
Users and system administrators have different levels of access rights
Some users allowed to read but not edit files
Encryption: hard drives and removable media
Memory protection: prevents programs being able to view/overwrite other programs’ data stored in RAM
Security updates—automatically downloaded and installed
Utility software
Keeps OS working well—perform extra functionality and housekeeping tasks that keep computers running efficiently
Includes:
Encryption software
Defragmentation software
Data compression
Disk clean-up tools
Disk formatters
Anti-virus software
Utility software: encryption software
- organisations use email encryption:
- Accountants discussing financial information of companies
- Sharing confidential internal files
- Encrypt entire hard disks
- Encrypt files and folders on a portable disk, eg. USB removable storage
- Encrypt communication with Eb sites
- Encrypt data in an organisation’s database—sensitive data—passwords
Utility software: defragmentation software
- read times are far faster
- Free space is also in one place so new files do not need to be fragmented
Why is defragmentation good
When a file is ‘fragmented’:
In order to read the file, the drive head will need to move to more locations
This makes it far slower to access files and programs
Defragmenting the hard disk reorganises files so they are stored together:
Read times are far faster
Free space is also in one place so new files do not need to be fragmented
Utility software: data compression software
Utilities such as WinZip enable users to compress and decompress files or folders:
Reduces the amount of storage space needed on a disk
If sending the files, it reduces the amount of data that is sent
Compression may allow attachments to be sent via email that would otherwise have been larger than a file-size limit
More data can be stored on backup media
Embedded systems
embedded computer is a single microprocessor that includes RAM, ROM and a CPU
Embedded systems examples:
Washing machine
Interior light in a car
MP3 players
Digital watches
Calculators
Embedded vs non embedded:
CPU speed
Software
Storage
Reliability
Embedded:
Typically slow
Has one purpose and cannot install new software
Programs stored on ROM
Typically very reliable—e.g a microwave should not have a bug that changes defrost to full power
Non-embedded:
Typically very fast
New software can be installed
Programs stored on hard drives
As it runs many software programs it may be less reliable and need restarting the device
High level programming languages
Python, Visual Basic, C#, Java, C++, PHP, Delphi, Logo
Query languages
SQL
Markup languages
HTML, XML
Low level programming languages
Assembly language
Machine code vs assembly
Machine: written all in binary—difficult and time consuming
Assembly language: creates programs more easily
Machine code and processors
Processors can only execute instructions in machine code
Assembly languages
- processor-specific
- Has to be translated into machine code before it can be executed
- Used for software in embedded systems, e.g washing machine, used to control specific hardware components, e.g. device drivers
High level vs low level
- high level
- easy to learn
- Programs written faster
- Easier to understand and debug
- Need to by translated into machine code in order to run
- Low level
- Runs very quickly
- Requires less RAM
- Used to control and manipulate specific hardware components
Assembly language uses
Allows the programmer to precisely control any instruction on the processor
Means that programs can be made to be very efficient
For instance, when a graphics device driver is programmed to run quickly and make use of all the advance features
High level languages explain
Must be translated into machine code in order to run
A single statement usually translates into several machine code instructions
Translation is done by a program which may be either a compiler or an interpreter
Translators
Compiler
Interpreter
Assembler
Translators: compiler
- translates high level into machine code
- Machine code produced can be saved on a storage device and run whenever required
Translators: interpreter
- translates high level into machine code
- No object code is produced
- Executes immediately
- If it reaches a line with syntax error it stops and displays an error message
Translators: assembler
Assembly code to machine
Interpreter vs compiler vs assembler
Input
Output
How it works
Speed of execution
What end users need to run program
Source code
Interpreter:
High level language
No output—program runs straight away
Translates source code and immediately runs it
Slow as needs to be translated each time it is run
Each end user needs the interpreter and the program
End user can see the source code
Compiler:
A high level language
Machine code
Compile source code so it can be run later
Fast as it just runs the machine code
Users need just the compiled program
End user can’t see the source code
Assembler:
Assembly language
Machine code
Assemble source code so it can’t e run later
Fast as it just runs the machine code
Users need just the compiled program
End user can’t see the source code
The main components of a computer
Main memory—RAM, ROM
Input devices—microphone, keyboard, keyboard
Secondary storage—CD, SSD, HD,DVD
Output devices—printer, screen, scanner
CPU
Runs instructions of a program
Runs one instruction at a time
Carries out billions of instructions per second
Von Neumann architecture
Control unit
Arithmetic-logic unit (ALU)
Registers
Clock
Buses
Von Neumann architecture
Program instructions and the data the programs are using are both stored in the same memory
The CPU accesses both instructions and data from the same RAM
Control unit
- coodinates and controls all of the activities taking place within the CPU
- Decodes instructions and executes them
- Receives signals from the system clock
- Directs the timing and control of other parts of the CPU
Registers
Carries out operations
A register is a very fast memory location in the CPU
Small memory
Stores a piece of information for a short time
Arithmeric logic unit (ALU)
Arithmetic operations: addition, subtraction, multiplication, division
Logical operations: comparing one data item to another
Clock (cs)
- controls the timing of the processor
- A faster clock speed will result in the faster processing of instructions
Buses (cs)
- A bus is a set of parallel wires connecting two or more components of the computer
- address busStores the address of the memory or device controller to be read from or written toOne way only bus
- Data busCarries data throughout the computer system
- Control busUses control signals to control all activities within CPU
What affects CPU performance
Clock speed—cycles per second measured in hertz
Number of cores—the number of duplicate processing units placed in one CPU
Cache size—memory on the CPU that is faster than RAM but slower than registers
Multi-core processors
A dual-core processor has two processors in the same integrated circuit, linked together
- a dual core processor has the potential to perform tow instructions at the same time
- allows twice as many instructions to be executed, but doesn’t always perform at this rate as software may not be able to take full advantage of both cores
Effector on speed of cache
Ram = relatively slow memory to access—further ways form the processor than cache
Takes longer to retrieve an instruction/data from RAM than cache
Program instructions and data that are fetched are stored in cache in case they are needed again soon
Fetch decode execute cycle
Instructions are placed in RAM
The next instruction is fetched
It is decoded by the CU
The CU tells the relevant components to execute the instruction
RAM random access memory
Main memory
Can be read from and written to
Access to RAM is much faster than a hard drive
Will normally store:
OS currently in use
Software currently in use
Data which the software is using
When computer is turned off, data in RAM is lost—RAM is volatile
All programs and data are stored permanently on non-volatile storage
ROM read-only memory
Permanently holds data
Data is read from ROM, but cannot be written to it
Non-volatile
Stores:
Initial program that is run when the computer is turned on—the bootstrap
Tells the computer where it will find the operating system on the hard drive
Stores the basic input/output system (BIOS)
BIOS can run without a hard drive/other secondary storage
Controls basic technical configuration of the computer such as the processor speed and system time
RAM vs ROM
Size
Used to store
Read ability
Write ability
Volatile
RAM:
Typically 4GB - 32GB
Running programs and operating system
Yes
Yes
Yes
ROM:
Typically 4MB - 8MB
BIOS and bootstrap
Yes
No
No
Memory speed
The speed that data can’t e accessed changes through the different components in a computer
Secondary storage
Non volatile
DVD
Cd
Tape drive
SD
Hard drive
Memory vs secondary storage
Main memory Secondary storage
Volatile (RAM) Non-volatile
Very fast to read/write Slow to read/write
Expensive per GB Cheap per GB
Stores data and programs currently Permanently stores data to be used
in use by the computer system
Directly accessible by CPU Not directly accessible by CPU
Storage methods of secondary storage
Magnetic
Optical
Solid state
Storage methods of secondary storage: magnetic
Mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape
Storage methods of secondary storage: optical
Lasers read and write data using light
Storage methods of secondary storage: solid state
Data is recorded onto solid memory chips without any moving parts
Magnetic storage advantages, disadvantages, uses, capacity
Advantages:
Cheap, large storage capacities, relatively fast write speed
Disadvantages:
Lots of mechanical parts, durability and issue, sealed unit due to disk head and platter precision and not very portable
Uses:
Personal computers, storage of large quantities of data
Capacity:
500GB - 12 TB
Optical storage advantages, disadvantages, uses, capacity
Advantages:
• Cheap, very easily portable, takes up little space physically
Disadvantages:
• Less storage capacity compared to other types
• Easily damaged / scratched, requires a CD reader
• Slow write speeds
Uses:
• Songs, videos and other multi-media storage, backup and archiving of data
Capacity:
• CD-ROM - up to 720 MB
• DVD - up to 8.4 GB (dual layered disk)
• Blu-Ray- up to 50 GB (dual layered disk)
Solid state drives basic features
Solid-state drives use non-volatile flash memory to store information
• Very fast read/write speeds as it doesn’t need to wait for a disk to spin to the correct location and an arm to move
• No mechanical or moving parts meaning these disks are very durable
SSDs advantages, disadvantages, uses, capacity
Advantages:
• Highly durable, no moving parts, very fast read/write speeds, no noisy fan or drive arm, faster start up times
Disadvantages:
• More expensive than magnetic hard disks, similar storage capacity as magnetic disks
Uses:
• Higher end computers
• Laptops
• Smartphones and tablets
Capacity:
• 100GB - 16TB
Flash memory
Low cost
Potable
No moving parts
Durable
Cloud storage
Refers to saving data in an off-site storage system maintained by a third party, e.g Dropbox, Google drive
Data that is stored on cloud storage can be located anywhere in the world
Cloud storage advantages
Easy to use, most companies offer apps for desktop and mobile devices to manage their data
Companies offer a high data storage capacity
Convenient to use, users can access data from anywhere with an internet connection
Backups are carried out by the cloud provider so save the need for local backups
The data storage capacity can be increased easily as users need more
Cloud storage disadvantages
Data cannot be accessed without and internet connection
A company needs to trust that the security of the cloud service is enough to stop a data breach—they won’t be directly able to control the security of the data
Uploading and downloading data could take a long time and is dependant on the available bandwidth of the user’s connection
