Computer Systems Flashcards
What is computer?
A computer is a machine that processes data
Define hardware
The physical components that make up your computer system
Define software
The programs that a computer system runs
What is system software?
Systems software is software that controls the computer system and can control various hardware and other programs
What is application software?
It is a type of computer program that performs a specific personal, educational and business function. Each program is designed to assist the user with a particular process
Give some examples of application software
Word Processors Web browsers Email clients Games
What is an embedded system?
Embedded systems are computers built into other devices
Explain the role of the control unit in the CPU
To execute program instructions by following the fetch-decode-execute cycle Controls the flow of data inside the CPU (to registers, ALU, cache) and outside the CPU (to main memory and input/output devices)
What does ALU stand for?
Arithmetic Logic Unit
What does the ALU do?
Completes simple addition and subtraction Compares the size of numbers Can do multiplications and divisions using repeated addition and subtraction Performs logic operations such as AND, OR and NOT Performs binary shifts
What is cache?
Very fast memory in the CPU
What is cache used for?
To store regularly used data so that the CPU can access it quickly the next time its needed
Describe the function of the clock
Used to synchronise when instructions will be carried out (like a metronome)
What is a bus?
A collection of wires that are used to transmit data between components of the CPU and other parts of the computer system
Describe what happens at each stage of the CPU fetch-decode-execute cycle
FETCH - The control unit reads the memory address of the next CPU instruction. The instruction stored in that address is copied from memory to one of the registers. The memory address in the control unit is incremented to point to the address of the next instruction, ready for the next cycle DECODE - The instruction that was copied from memory is decoded by the control unit. The control unit prepares for the next step EXECUTE - The instruction is performed
What is volatile memory?
Temporary memory that requires power to retain its data
What is non-volatile memory?
Permanent memory that keeps its contents even when it has no power
What does RAM stand for
Random Access Memory
Describe how RAM is used in a computer system
To store all data, files and programs when they’re being used
What is ROM?
Read-only memory is a type of non-volatile memory used in computers and other electronic devices
Explain why ROM is required by a computer system
It contains all the instructions a computer needs to properly boot up. These instructions are called the BIOS (basic input output system)
Which usually has more RAM: an embedded system or a non-embedded system?
Non-embedded systems
What characteristics of a processor may affect its performance?
Clock speed CPU cores Cache size Cache type
Define primary storage
The memory areas that the CPU can access directly
Define secondary storage
Non-volatile storage that isn’t directly accessible by the CPU
Give some examples of primary storage
CPU registers Cache ROM RAM
Give some examples of secondary storage
Magnetic hard disk drives Solid state drives CDs SD cards
What are the advantages of a SSD compared to a HDD?
SSDs are faster SSDs don’t need defragmenting SSDs are more shock proof than HDDs HDDs make some noise, SSDs are silent
What are the advantages of a HDD compared to a SSD?
HDDs are cheaper Both are high capacity, but HDDs are higher HDDs have a longer read/write life than SSDs - SSDs can only be written a certain number of time before they begin to deteriorate
Why might someone choose magnetic tape as a form of storage?
It has a very high capacity and an extremely low cost per GB
List some uses of flash memory
Cameras Smartphones Tablets
What are the pros of optical disks?
They’re very cheap per GB Portable Won’t be damaged by water or shocks
What are the cons of optical disks?
They are easily scratched Modern devices don’t have optical drives They can’t compete with flash storage devices due to their low capacity per disk, very slow read/write speeds and poor reliability of RW disks
What are the pros of cloud storage?
Users can access files from any connected device Files can be shared with others or made public Easy to increase how much storage is available No need to buy expensive hardware to store data Cloud host provides security and backups for you
What are the cons of cloud storage?
Need internet connection to access files Upload/download speed depends on bandwidth Stored data can be vulnerable to hackers Subscription fees for using cloud data may be expensive in the long term
What are the functions of an operating system?
To communicate with input and output devices via device drivers Provide a platform for applications to run on, and a user interface Control memory management and allocation Organise the CPU and its processing tasks Deal with file management and disk management Manage system security and user accounts
Explain how device drivers are used in a computer system
Device drivers act as a “translator” for the signals between the OS and the device
Describe how the OS manages applications
Provides a platform for applications to run on and multitask Allows applications to access hardware, peripheral devices, RAM and secondary storage Provides a user interface that applications are accessed through
Describe how the OS manages memory
Decides if applications or features have been used recently - if not they may be removed from memory Manages how much RAM a program has access to When running multiple applications at one, will make sure that they don’t overwrite or interfere with each other by allocating certain applications certain memory addresses, keeping their processes in separate locations
Describe how the OS manages the CPU
Scheduling to determine the most efficient order for the CPU to execute instructions Interrupts the current CPU process if a higher-priority process becomes available
Describe how the OS manages files and disk space
Manages the hard disk - splits the physical disk into storage sectors, decides which sector to write data to and keeps track of free space on the disk Organises and maintains the hard disk with utility software like defragmentation software
Give ways in which an OS might keep your files secure
User account control Anti-theft measures Passwords Pins Fingerprint scanners Retina scanners
List some types of utility software and explain what they do
Defragmentation- puts the files back into one block and collects the free space together Disk health - scans the drive for problems and fixes issues where possible Compression - reduces the size of files so they take up less disk space Encryption - scrambles (encrypts) data to stop third-partners from accessing it Backup - copies the computer system’s files and settings and stores them externally so that they can be restored in the event of data loss Virus scanners - inspects each file on your computer, looking for virus System cleanup - goes through and gets rid of temporary files left on your hard drive which can end up taking up lots of space unnecessarily
Give some examples of system software
Operating systems Utilities
What is the Von Neumann architecture
It consists of a single shaped memory for programs and data, a single bus for memory access, an arithmetic unit and a program control unit.
AND gates
NOT gates
OR gates
NOR gates
How does a magnetic hard drive operate?
It consists of a number of disks coated in a magnetic material.
They spin at around 7200 rpm.
The data is encoded into bits and written onto the surface as a series of changes in the direction of the magnetisation.
How does optical storage work?
Data is written onto the disc by a laser and is read from the disc by another laser.
How do SSDs work?
There are no moving parts, unlike the spinning disc inside a magnetic drive. A SSD uses microscopic electronic switches to store data.
SSDs use switches called floating gate transistors. These create a special cage (the gate) that traps the electron flow within it.
