computer systems (CS) Flashcards
how do you calculate the range of positive integers using n bits
from 0 to (2^n) - 1
what is the range of 8 bit positive integers
0 to 255
how do you calculate the range of both positive and negative integers using n bits
from (-2^n-1) to (2^n-1 -1)
what is the range of 8 bit positive and negative integers
-128 to 127
convert 10101111 to denary using two’s complement
-81
convert -108 to binary using two’s complement
10010100
what is floating point representation
a way to represent real numbers
what does the exponent do in floating point representation
indicates how many places the binary moves from left to right
how is the floating point binary number typically stored
1 bit for sign
fixed bits for mantissa (16)
fixed bits for exponent (8)
they are all stored together
what does increasing the mantissa size do
it increases the precision but decreases the range
what does increasing the exponent size do
increases the range but decreases the precision
what is the fetch execute cycle
the process where an instruction is retrieved from memory, decoded and carried out
what are the steps in the fetch-execute cycle
- the processor sets up the address bus with the required address
- the processor activates the read line on the control bus
- an instruction is fetched from the memory location using the data bus and stored in the instruction register
- the instruction in the instruction register is then interpreted by the decoder and carried out
what are the 4 factors affecting system performance
number of cores, width of data bus, cache memory and clock speed
how does the number of cores affect performance
more cores allow more instructions to be processed at once, dual-core is slower than quad-core
how does the width of the data bus affect performance
a wider bus transfers more data at once improving performance
what is cache memory
fast memory near the processor, improves efficiency by storing frequently used instructions
what is clock speed
the number of cycles per second, higher speed = more instructions per second
what does the computer misuse act 1990 cover
protection of computer systems + data from misuse or criminal activity
what are the offences under the computer misuse act
- unauthorised access to computer material
- unauthorised access with intent to commit further offences
- unauthorised modification of programs and data
what are cookies in terms of security risks
small files used to rack user activity and raise privacy concerns
what are impacts of a denial of service (DoS) attack
slows systems, blocks access, disrupts operations, cause loss of revenue
what is a asymmetric encryption
uses a public key to encrypt and a private key to decrypt
what is the role of a certificate authority
confirms the authenticity of websites and verifies identity
