computer systems Flashcards
what are the two ways of storing characters
ascii and Unicode
what are the two ways of storing characters
ascii and unicode
what are pros and cons of ascii
ascii code is uses 8 bits to store a character meaning it takes less storage than uniicode but can only represent 256 possible characters
pros and cons of Unicode
Unicode uses 16 bits and therefore can represent 65536 possible characters but takes up twice the storage that ascii code uses
what are bitmapped graphics
bitmapped graphics store each pixel and what colour it is, no matter what the photo is it will always take up same amount of storage
what are vector graphics
vector graphics are when the geometric attributes for each object are stored
what are the steps in the read from memory event
processor sets up address lines with the address of item to be retrieved
processor activates real line on control bus
the contents of the memory location are passed along the data bus to the processor
if the processor receives an instruction it is decoded and executes
what is the ALU
the arithmetic logic unit which is responsible for processing and manipulating data arithmetic and logical comparisons (AND OR NOT ) are carried out here
what is a register
a register is very fast storage location inside the processor itself
what are the registers
MAR- memory address register
MDR- memory data register
PC- program counter
IR- instruction register
SP-stack pointer
A-accumulator
A,X,Y- general purpose registers
SR-status register
what does the control unit do
responsible for the fetching, decoding and execution of instruction in the IR by sending control signals
what lines does the control unit contain
read- reads memory that is on adress line
write - puts addres on address line in memory into write mode
clock- ticks continuously and is used by control unit for timing faster the clock the faster the processor e.g 3 ghz processor faster than 2 ghz
reset - clears all internal processor registers and starts fetching instructions from a predefined space
interrupt - carries signal to processor which causes current state of processing to be saved in temporary area. the processor deals with what made the interupt then continues processing what is saved in temporary area
what are the types of computer storage
Registers
cache
Ram
Backing / secondary
Steps in write to event
Set the data bus with the data to be written
Set the address bus with the address of the data to be written
Set control bus to write
Data is written in desired address
