Topic 6 Flashcards
Types of Computer Systems
1) Mainframe
2) Servers
3) PCs
4) Sub-laptops
5) Cell phones
6) Tablets
7) PDAs
8) Digital cameras
Mainframes
Processor: Thousands of cores
Primary memory: Vast amounts
Secondary memory: Vast amounts
Common use:
1) Used in large companies
2) Used for weather/financial models and predictions
3) Used to ‘virtualize’ smaller computers
4) Main players: CRAY/IBM
Servers and Server farms
Processor: Many high spec PCs running in parallel (3-4GHz)
Primary memory: Big capacity
(32GB+ per machine)
Secondary memory: Terabyte per machine
Common use:
1) Used to ‘serve’ networks
2) Used as data centers for ‘cloud storage’
3) Size varies according to use
PCs (Desktop)
Processor: Single processor (multiple cores) 1-4 GHz
Common use:
Used in companies/schools (where portablility is not needed)
Can be expanded by adding expansion cards (graphics cards)
Used to be the most common type of personal computer
Sub-laptops (those mini ones like tablet notebooks for kids)
Processor: Single/multiple core (1-2 GHz)
Common use:
1) Fueled by the ‘netbook boom’ of early
2000s (before tablets)
2) Runs stripped down OS (Linux,
Chrome OS)
3) Portablity and battery life are key features
Cell phones/Mobiles
Processor: Single/Multicore
Primary memory: 1-3 GB
Secondary memory: Usually limited, but can be upgraded
Common use:
1) Most common personal computing device in the world
2) Getting more capable, rivaling
PCs/laptops
3) Biggest constraint is screen size and input options (lack of physical keyboard)
Tablets
Processor: Single/Multicore
Primary memory: 1-4 GB
Secondary memory: Usually limited, but can be upgraded
Common use:
1) Very common for media consumption
2) Getting more capable, rivaling
PCs/laptops
3) Biggest constraint is lack of physical keyboard
PDAs (before ipods but similar)
Processor: Single core (<1GHz)
Primary memory: Limited (<500MB)
Secondary memory: Limited
(<128MB)
Common use:
1) Not used that much any more
2) Used for calendars/emails
3) Was overtaken by smartphones and mobiles in early 2000s
Digital cameras
Processor: Single core
Primary memory: Limited
Secondary memory: Expandable through use of memory cards (SD/Compact flash/Memory Stick)
Common use:
1) For higher end photography
2) Most digital cameras now integrated in mobile phones/laptops/tablets
Managing primary memory
1) The OS has to ensure that each process (program) runs in its own allocated
memory space.
2) If programs interfere with each other’s memory space it could cause many problems including corruption and security issues.
Virtual Memory
Virtual memory is a feature of an operating system (OS) that allows a computer to compensate for shortages of physical memory by temporarily transferring pages of data from random access memory (RAM) to disk storage.
Managing Secondary Storage
1) The OS manages the secondary storage by providing structure and access methods to these
structures
2) We often refer to this as the folder-structure but in some OSes it is referred to as the directory
structure.
2) The OS also manages the security access of these folders
Function - Provides an interface
User interface is used to interact with the computer to performs various tasks.
User gives commands to computer and enters the data into computer.
Types of Operating Systems
Based on the user interface, there are two types of operating systems.
Graphical User Interface Operating System (Windows)
Command Line Operating System (Linux Terminal)
Interrupts
1) An interrupt handler is a function in of the OS or a device driver, whose execution is triggered by the reception of an Interrupt.
2) Interrupts are used to handle high-priority conditions that require the interruption of the current code the processor is executing.
3) For example, pressing a key on a keyboard, or moving the mouse, triggers interrupts that call interrupt handlers which read the key, or the mouse’s position, and copy the associated information into the computer’s memory.
4) An event that is triggered by external components other than the CPU that alerts the CPU to perform a certain action
5) When an interrupt occurred, the interrupt handler executes
6) Can occur at any time
7) Interrupt-request line indicates that device needs a service
What is polling?
1) An activity of sampling the status of an external device by a client program as a synchronous activity
2) In polling, the CPU provides the service Occurs at regular intervals
3) Wastes lot of CPU
4) It is inefficient in polling, when the CPU rarely finds requests from the devices
