Theory - Computer Systems Flashcards
Input process output model
Input -> Process -> Output
^ ^ v I
I Storage I
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Main memory (RAM / random access memory)
^ v
Input -> Process (by CPU) -> Output
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Computer system
System that takes a set of digital inputs, processes them and creates a set of outputs
Done by a combination of hardware and software
Combination of hardware and software components allow input, processing and output of data
How data enters a computer system
When a user adds an input
Examples of input devices
Mouse
Keyboard
Microphone
Camera
Another name for CPU (central processing unit)
Processor
Role of a program in a computer system
Programs handle user inputs
Output
Result from input
Can be displayed through many output devices, such as screens for visuals and speakers for sound
Why processed data is sometimes stored rather than output
Data may not be needed instantly
Data could also be stored for later use
Dedicated system
Computer system made to do 1 specific task
Such as a computer controlling a robotic arm in a car factory
Embedded system
Small computer that is part of a larger system with one purpose
Dedicated system which is part of a larger mechanical or electrical system,
such as a washing machine controller and a digital camera processor
General purpose system
Systems capable of performing many different tasks
Used for many different purposes, such as playing music, games, email, internet,
such as a personal computer, tablet, smartphone
Hardware
Physical components used in a computer system for input, processing and output.
Such as a display, mouse, motor, printer, CPU or motherboard
Software
Program code which is executed on the CPU
Operating systems and applications are both types of software
What is needed to make 2 computer systems communicate with each other
Internet connection
Advantages of embedded systems
• Easy to mass produce
• Highly reliable
• Small in size
• Cheaper than conventional computers
• Fast operation
• Improved product quality
• Optimises use of system resources.
• Low power operation
Disadvantages of embedded systems
• The embedded systems are hard for maintenance as it is use and throw device.
• It has no technological improvement.
• Less power supply durability if it is battery operated.
• It has hard to take backup of embedded files.
Utility software
Security: Anti virus, firewall, spyware detection, encryption
File organisation: Archiving, backup and store
Clean up: Delete tmp, cache, internet files, downloads & installers, recycle bin, defragmentation, compression
Diagnostics: Task manager, disk usage viewer
Customisation and add-ons: Eye-candy: change the appearance of an app without changing its functionality.
Helper app, and new features to existing apps, make them faster/easier.
library programs
System software used to oversee the maintenance of a computer
e.g. resource management, data organization
Low level programming language
Machine code - The binary language that software is written in and that CPUs use to carry out tasks
Assembly language - programming language for computers or other programmable devices
Exact control over the hardware allows optimisations to be made which result in very fast code which takes little memory space.
produce shorter and faster code which is useful for computers with low specifications, especially in embedded systems.
multitasking
The ability of an operating system to do more than one task at once.
allows the user to have several different applications running at the same time
operating system (OS)
Pre-installed software essential for the running of the computer, e.g. Linux, Microsoft Windows, Mac OS X. The OS software depends on the hardware used, e.g. iOS 17 on iPad
Processor / task / process management;
• Memory management;
• I/O device management;
• Applications management,
Security management;
• File / storage management;
• Network management;
A. Provides a user interface
peripheral
A separate input, output or storage device that is connected to perform particular tasks. For example, printer, USB drive, keyboard.
security
A type of system software that provides protection from malicious software threats and data loss, e.g. firewall
software
Any program or application that allows users to interact with hardware and give it instructions
SPOOL
Acronym: Simultaneous Peripheral Operation On Line
The activity of keeping various peripheral tasks in a special waiting bay to allow slower tasks to catch up without slowing down the computer
system software
Software used to control computers and operate the programs installed on them, e.g. operating system software, utility program
utility programs
System software that provides a repository of frequently used code that can be accessed by different programs
Antivirus
software that detects malware in a computer or computer system and destroys it.
Disk defragmenter
File might be stored across multiple physical locations on the disc (1), which causes access speed to be slower
Defragmentation moves parts of a file (1) in order to store all parts in adjacent locations
This software reduces the number of times the disk needs to be accessed so that the file loads
This increases the performance of the computer system
System cleanup
This is used to delete files, such as internet files and cached data
Automatic update
This keeps the computer up to date with the latest software and operating systems.
3 processes of the CPU
FETCH instruction from main memory
DECODE the instruction
EXECUTE the instruction
Purpose of the CPU
sorting and searching data
performing calculations
logical decision-making
synchronising data on different devices
control of input/output and storage devices
Inside a Central Processing Unit (CPU), transistors are arranged into circuits to perform operations such as calculations when electricity is passed through them.
For example, transistors can be arranged to form an ‘adder’ circuit that can accept two binary numbers, and output the sum of their values.
Modern CPUs contain over 3 billion transistors, allowing them to perform billions of calculations per second.
When a program is run, where is it loaded into
RAM - main memory
Random access memory
5 registers involved with the fetch decode execute cycle
Program counter (PC)
Memory address register (MAR)
Memory data register (MDR)
Current instruction register
Accumulator
What happens during the fetch operation
program you want to run is loaded into RAM
starting address location is loaded into memory data register
program counter value is copied into program counter
Control Unit then loads address on to memory address register
And then sends a signal to Read address
The instruction at that address is passed across the data bus and copied into the
The instruction in the MDR is copied into the
So that it is ready to use during next stage (Decode)
The program counter Is incremented by one location so that it is ready to begin the next fetch cycle.
How may programs can be running in the main memory / RAM
1 or more
