computer systems Flashcards
define hardware
physical components of a computer
e.g
keyboard
monitor
mouse
define software
the programs that run on a computer, control the hardware
high level language
-any program written in high level is called source code
-need to be translated to machine code
-easy for humans to understand(less complex)
e.g:
python
java
c++
low level language
-directly translates to machine code
-difficult to understand
-execute quicker
e.g:
machine code (binary)
assembly language
translators
-convert high level language to machine code
3 types:
interpreter
compiler
assembler
compilers
-takes source code and translates it to machine code in one go
Advantages:
-compiled programs=run quick, as already translated
-can be supplied as an executable file
-optimise code- runs quicker, takes up less memory space
Disadvantages:
-recompiled every time program is changed
-source code compiled on one platform won’t run on another
interpreters
-translates to machine code one instruction at a time
Advantages:
-instructions executed as they’re translated
-errors quickly noticed// when error is found, program stops+ user is notified
Disadvantages:
-runs slowly
-has to be translated each time it’s run
-no executable file, so source code has to be supplied (can be modified easily)
-not optimised code
assemblers
-translate assembly language (low level) to machine code
-create 1 machine code for each assembly instruction
AND gates
-output only 1 (TRUE) if both inputs are 1 (TRUE)
-look like sideways U
OR gates
-output = 1 when one or both inputs are 1
-looks like crescent
NOT gates
-only one input
-output =0 when input = 1 and vice versa
-triangle+circle
system software
-any software that helps run/manage
e.g:
security software
file management
application software
-allows user to perform a task
e.g:
word
browser
operating systems
-collection of programs that manage+ control the computer
roles of operating systems
-control hardware components
-provide platform for software to run on
-provide user interface
-manage processes
-manage memory
-manage input+output devices
-manage apps
-manage security
Fetch Decode Execute Cycle
- The memory address held in the program counter is copied into the MAR (memory address register)
- The address in the program counter is then incremented - increased - by one. The program counter now holds the address of the next instruction to be fetched.
- The processor sends a signal along the address bus to the memory address held in the MAR.
- The instruction/data held in that memory address is sent along the data bus to the MBR/MDR(memory data register)
- The instruction/data held in the MBR/MDR is copied into the CIR(current instruction register)
- The instruction/data held in the CIR is decoded and then executed. Results of processing are stored in the ACC (register used by ALU to store calculation results)
- The cycle then returns to step one.
ALU
-performs arithmetic operators+logical decisions
-gateway between primary memory and secondary storage
control unit
-fetches decides + executes instructions
-issues control signals that control ha edward
moves data around system
registers
-small amounts of high speed memory in cpu
-used by processor to store small amounts. of data
e.g:
-address of next instruction
-results of calc
-current instruction being decodes
RAM (random access memory)
-volatile
-when computer =off, RAM content = lost
-written to and read from
cache
-small amount of high speed RAN
-built directly in processor
-temp. holds data
-faster processing as processor doesn’t have to wait for data + instructions to be fetched from RAM
bus
-used to send data from diff parts of the computer
3 types:
-address
-data
-control bus
clock
-sends out electrical pulses to synchronise hardware components
frequency of pulse=clock speed:
-measured in hertz
-higher frequency=more instructions
factors affecting performance
Clock speed:
-higher speed=more FDE cycles performed=more instructions
-overclock-when cpu clock is sped up, can cause long term damage
Cache size:
-bigger cache=less time processed waits
Number of cores:
-each core=can FDE its own instruction
main memory
-main storage region of a computer that cpu can directly access
-has RAM and ROM
ROM (read only memory)
-non volatile
-can’t be written to
secondary storage
-non volatile
-long term storage
-saves memory
-can store programs and data for later use
Solid state storage
-SSDs, usb sticks
-made from silicon microchips, data stored by holding an electrical current in a transistor
-can be written to
-non volatile
-external secondary storage
-fast+expensive
magnetic
-cheap, high capacity, durable
-damaged if dropped
-hard disks that use magnetic fields to magnetise individual sections of a spinning metal disk
-read+written
optical
-uses laser ti scan surface of spinning metal+ plastic disc(divided in tracks w lands and pits)
->sensor scans+checks reflected light
-rom media (pre-written data, like movoes)
-Read (r)media=blank read/write RW=disc can be written to more than once
cloud storage
-storing data at a remote location
—> when files are sent to cloud they are sent to a server connected to the internet
-files can be uploaded+downloaded as required
Adv+ dis of cloud storage
ADV:
-data accessed from anywhere w internet connection
-businesses running cloud storage manage backups and security
-additional storage can easily be added
DISADV:
-hacker can potentially access data from a wehere w wifi
-failed internet= no access
-relying on others for security
embedded systems
-small computer part of a larger system/machine
—controls device and lets user interact w it
-have 1/limited number of tasks
embedded systems
-small computer part of a larger system/machine
—controls device and lets user interact w it
-have 1/limited number of tasks
