computer systems Flashcards
how are floating point numbers stored
mantissa and exponent
how many bits does extended ASCII use
8 bits
what are controllable character and printable character
controllable = signals that do not appear as printed symbols in the text
printable = letters, numbers and symbols that you see on the screen.
how to calculate the space needed to store the message in bits
no of letters x 8 bits
to convert into bytes = no of letters x 8 bits / 8
how is a bitmap graphic stored
in a grid of pixels where each pixel has a colour associated to it
how is vector graphic stored
in vector graphic image is made up of shapes called objects and each object has a list of attributes
registers
small amount of temporary memory inside the processor, holds data and instructions while they are being processed
arithmetic and logic unit
does all calculations and logic/comparisons
control unit
decodes and executes instructions.
Keeps all of the other parts of the processor in time with its clock
main memory
divided into memory locations. Each location has a unique memory address. Connected to the processor by address and data buses.
processor
dos all the thinking of the computer - 3 parts ALU, control unit and registers
address bus
carries addresses in one direction from processor to main memory
data bus
carries data and instructions in both directions between memory and processor
state the part of the processor that keeps other parts in time using the clock
control unit
state the bus that carries addresses from the processor to main memory
address bus
explain how memory is organised in the computer
memory is organised into separate locations or addresses and each is unique
why are programs translated
computer only understands machine code. Before the program can be run, it has to be translated into machine code by an interpreter or a compiler.
advantages of interpreter
- translates a line of code at a time highlighting the errors in the line. therefore being easy to fix errors
- you can run the interpreter without leaving the editor
advantages of compiler
- translates code all at once then tells u if theres any errors
- saves time as it doesnt need to be translated everytime its been run
- takes less memory to run since it doesn’t need to be translated everytime
disadvatage - cant be edited, if selling compiled version wont be able to see orginial or edit original version
state which translator type makes it easier to test the code without leaving the editor
interpreter
explain the role of machine code when writing and running a program you have written
communicates the programmes instructions in a way that the computer understands
3 ways to save computer energy
- turn brightness down on monitor
- standby/rest mode when not using
- set to power down at a certain time of day
- excess tabs can be deleted
firewalls
a software or hardware that restricts access to your network and decides what data is allowed through the connection. protect you against hackers not virus
encryption
a way to protect data. the encrypt data becomes coded, or unreadable, so that only the intended recipient can understand it.
two precautions that can be used to secure data
encryption and firewall
state which security precaution would be used to protect a network from hackers
firewalls
Explain how encrypting data can make it secure
the data would be unreadable so only the intended recipient can understand it
anti virus software
scans computer to detect and remove viruses
JPEG advantages
lossy compression
greater colour depth
compression rate can be changed
GIF advantages
lossless compression
can change colour depth
animated
transparency
why are low-fidelity prototypes used when designing a website
- gives potential end users of the
finished product an indication of
how the product will look - allows navigation structure to be
tested - confirm the position of page
objects are acceptable to the user
