Computer system Flashcards
What is a computer
A machine that processes data
What is hardware Give examples (4 examples given in my answer)
The physical parts of a computer Motherboard CPU Keyboard Screen
What is software
What are the main categories
The programs that run on a computer
System software:
Programs that are needed for the computer to function (ie operating system)
Application software (apps): Programs that enable a user to perform a specific task
What does a computer require in order to function
Both:
Hardware
Software
What is an embedded system
A computer that is built into another device to control it
Give examples of an embedded system
My answer gives 8
Washing machine Microwave Vending machine Traffic lights Lifts Smart meter (measures energy used) Sat Nav
CPU stand for
Central processing unit
What is a CPU
A microchip that sits in the middle of the motherboard and carries out (processes) instructions stored in memory by fetching, decoding and executing them one at a time
CPU architecture meaning
Describes main components (internal parts) of the CPU and how they interact with each other
Most CPU based on a design by ….. in ……
John Von Neumann
1945
What are the main internal components of a CPU
Control unit Clock Arithmetic Logic Unit (ALU) Registers Cache memory Primary memory (RAM) Secondary storage Buses
Control unit
Definition
Fetches instructions from memory and decodes them one at a time
Also controls the flow of data between the parts of a CPU, main memory, and input/ output devices
Clock definition
Ticks meaning
Measured in ….
Synchronises all parts of the CPU by sending electronic pulses at a constant rate
The number of clock “ticks” per second is called the clock speed and is measured in hertz
ALU meaning
Definition
Arithmetic Logic Unit
Carries out arithmetic calculations such as addition, subtraction and binary shifts.
Also do logical comparisons such as “greater than”, “less than”, AND, OR and NOT.
Registers
Definition
Small pieces of internal memory which hold instructions, data or memory addresses that are currently being used by the CPU.
What are the different types of registers
Names
Program counter
MAR (memory address register)
MDR (memory data register)
Accumulator
Program counter
Definition
Holds memory address of the next instruction to be executed
MAR
Definition and meaning
Memory address register
Holds the memory address of the next instruction to be fetched
MDR
Definition and meaning
Memory data register
Temporarily stores data fetched from main memory
Accumulator
Definition
Temporarily stored the result of calculations completed by the ALU until they can be saved to main memory
Buses
Definition
High-speed internal connection
Used to send memory addresses, control signals and data between the processor and other components
Cache memory
Definition
A small amount of very fast memory built into the CPU to store frequently used instructions.
This can save time by preventing it from having to fetch a common instruction from slower RAM every time it needs it
What is the process used by the CPU to carry out simple instructions
Fetch, decode, execute cycle
Explain fetch decode execute cycle
Fetch:
The memory address of the next instruction is copied from the program counter to the memory address register (MAR)
The instruction held in memory at this address is transferred to the memory data register (MDR)
The program counter is increased by one so that it is pointing to the next instruction ready for next cycle
Decode:
The control unit splits the instruction stored in the MDR into two parts called the opcode and operand
Execute:
The instruction is performed
RAM (other names)
Random access memory
System memory
Primary storage
Main memory
Volatile meaning
Lose all stored data if the power is turned off
What three things are RAM and cache memory? (In common)
Store instructions for CPU
High speed
Volatile
What is ROM
Read only memory
A small microchip fitted into the motherboard with just a few instructions to follow when computer is first switched on
2 main features of ROM
Non volatile
Read only memory
Start up / boot up / bootstrap ladder meaning
First instructions from ROM
Virtual memory alternate name
Fake RAM
What is fake RAM / why is it used
Instruction for applications in use are stored in RAM, more applications opened, more RAM used.
RAM memory is limited in size and can become full so the computer stops working.
Some systems can move data that has not been used recently from RAM to a location on secondary storage called virtual memory (fake RAM)
Why are computers slower when using virtual memory
(Fake RAM)
CPU cannot directly access data that has been moved to virtual memory, so this data must be moved back into RAM before it can be used.
This with relatively slow data transfer of secondary storage devices makes computers slower when using fake RAM
What does CPU clock speed do?
CPU clock synchronises all parts of the CPU by sending electronic pulses at a constant rate
The number of clock “ticks” per second is called the clock speed and is measured in hertz
What is overclocking
CPU clocks can sometimes be sped up slightly by the user.
This is called over locking and can cause damage to the CPU as it is working harder and producing more heat
What is the benefit / how do the number of CPU cores affect a computer
Adding another core to a CPU allows it to process more than one instruction at the same time
What is CPU cache memory
A small amount of high speed memory built directly within the processor
It is used to temporarily hold data and instructions that the CPU is likely to reuse
Allows for faster processing as CPU doesn’t have to wait for the data to be fetched from RAM
GPU meaning
Definition
Graphics processing unit
Computer graphics needs lots of processing due to complex maths involved
To help CPU carry out some of the processing GPU is added
Solid state secondary storage
SSDs can transfer data much faster than older storage systems ie magnetic hard disk drives (HDDs)
Why do computers need secondary storage
Non volatile
Data in secondary storage cannot be accessed directly by CPU so data must load into primary storage first
What are the categories of secondary storage and give examples
Solid state storage:
USB memory sticks, solid state drives
Optical storage:
CD, DVD and Blu-Ray discs
Magnetic storage:
Floppy disks and hard disk drives
What is solid state storage
Made from silicon microchips (flash memory) Written and overwritten like RAM Non volatile No moving parts Small Fast Durable
Solid state storage
4 advantages
3 disadvantages
4 common uses
Advantages: Small, lightweight Fast data transfer speeds Durable, reliable (no moving parts) Low power consumption
Disadvantages:
Expensive
Limited storage capacity
Limited number of write cycles
Common uses: USB memory sticks Memory cards Internal storage for smartphones Increasingly installed into laptops
Optical secondary storage
Optical disc drives use laser to scan surface of spinning disc made from metal and plastic
Types:
Read only discs:
Dats preprinted
Rewritable discs:
Blank
Optical storage
2 advantages
3 disadvantages
3 common uses
Advantages:
Cheap to produce
Small and lightweight (portable)
Disadvantages:
Easily scratched/ not durable
Sensitive to movement
Limited storage capacity
Common uses:
CD
DVD / Blu Ray
Video games
Magnetic storage
Old technology
Includes tapes, floppy disks and HDD
Coated with material that can be magnetised and uses electromagnet to read and write data
Magnetic storage
3 advantages
4 disadvantages
2 common uses
Advantages:
High storage capacity
Low cost
Reliable if kept still
Disadvantages: Bulky not portable Slow data transfer speeds Sensitive to movement High power consumption
Common uses:
Server storage
Server backup
Operating system
System software that provides an important link between computer hardware and the person using it
User interface
Operating system provides user interface to allow user to interact with the computer
Command line interface uses typed commands only
Graphical user interface (GUI) is designed for easy use controlled by mouse or touch screen - graphics used
Memory management and multitasking
Running application software
OS can run multiple apps at once
(Multitasking)
Does it by managing which parts of main memory are used for Each app
Also control which app the CPU processing instructions at moment
And can switch between apps quickly
Peripheral management and drivers
Operating systems uses device driver software to control or communicate with peripheral devices
Ie printer
When new device is connected operating systems will try to download and install appropriate device driver installer from internet
User management
OS controls who can use computer and what can do with it
Multiuser can support multiple accounts
Each user can have different access rights
Responsible for keeping computer secure ie password fingerprint or face recognition
File management
Computers store data in secondary storage as files OS responsible for organising files Renamed Moved Deleted Rearranged to structures using folders
File extension
Tells computer what type of days file contains ie jpg or png
Examples of utility software
Virus scanners System clean up Backup software Battery monitor Data compression Encryption software Disk defragmentation
Virus scanner
Inspect files on computer looking for viruses
Will download an up to date list of known viruses to look for
System clean up
Software will attempt to delete files on a computer that are no longer needed to free up storage space
Backup monitor
Regularly copy files from computer to external or online storage to protect against data loss
Battery monitor
Used to manage battery in a mobile computer such as laptop or phone
Usually switching to low power mode when battery nearly empty
Data compression
Used to compress or decompress files
Encryption software
Scramble files so that even if they are stolen from a storage device they cannot be used
Disk defragmentation
Organise files and fragments of files on a magnetic hard disk drive so that data can be accessed more quickly
Logic gate
AND
NOT
OR
Electronic switches in the CPU
Name
Transistors
How logic gates made
Combining transistors
Shape of gates
AND:
Semi circle with square
OR:
Fish fin shape
NOT:
Triangle with circle on end
