Computer Systems Flashcards
Address Bus
Used to identify a memory location to be read from or written to.
Arithmetic Logic Unit
Part of the processor where calculations and decisions are made.
Bi-Directional
Transfers in both directions.
Control Unit
Includes timing/control logic and an instruction decoder. It sends signals to other parts of the computer to direct the fetch and execution of machine instructions.
Control bus
Separate functions include initiating a read or a write to/from memory
Data Bus
Used to transfer data to and from the CPU.
Fetch-Execute Cycle
The memory address of the next instruction is placed on the address bus, read line is activated on the control bus, the instruction is transferred to the processor on the data bus, and instruction is decoded and executed.
Read Line
A function of the control bus which transfers data from the main memory to the processor
Registers
Temporary storage areas within the processor
Uni-Directional
Transfers data in one direction only.
Write Line
A function of the control bus which transfers data from the process or to main memory
Clock
A function of the control bus which provides the internal timer to synchronize events between system components.
Clock speed
Frequency at which a CPU executes instructions, measured in GHz.
Multi-core processors
More than one processors on the same chip, which gives them the capability of executing separate instructions at the same time
Increase data bus width
More bits can be transferred in one clock cycle
Cache Memory
A small amount of SRAM that sits between the processor and RAM in order to speed up data transfer by requiring less fetch-executes
Decimal equivalent of 10101010
170
Binary equivalent of 102
1100110
Range of positive and negative numbers using 7 bits
-64 to 63
Range of positive and negative numbers using 9 bits
-256 to 255
Range of positive numbers using 6 bits
0 to 63
An advantage of ASCII
Less storage required
An advantage of Unicode
Can represent more characters
A way of representing text using 8 bits
ASCII
Number of characters extended ASCII can represent
256
Number of characters Unicode can represent
Up 65,536
A way of representing text using 16 bits
Unicode
What affects the range in Floating Point Representation
Exponent
The larger the mantissa
The more accurate (or precise) the number
The larger the exponent
The greater range of numbers that can be stored
What affects the accuracy in Floating Point Representation
Mantissa
What would the mantissa be for this denary number 26320
0.2632
What would the exponent be for this denary number 26320
5
What would the sign bit be for this binary number 0.0001011
0
What would the 15 bit mantissa be for this binary number 0.0001011
1.011E+14
What would the 8 bit exponent be for this binary number 0.0001011
11111101
Increasing the bit-depth (colour-depth) means
More realistic image & larger file size
Increasing the resolution of an image means
Better quality image & larger file size
Two’s compliment equivalent of -67 is
10111101
The decimal equivalent of 10101111 in two’s complement
-81
Vector graphics
Stores an image as list of objects and their attributes
Bit map graphics
Stores an image as a 2D grid of pixels
Advantages of vector graphics
Smaller file size and resolution independent
Advantages of bit map graphics
Can be edited at pixel level
Adding extra detail to a bit map graphic
Does not affect the file size
Adding extra detail to a vector graphic
Increases the file size
Intelligent heating system
Saves energy and money by sensing when the house is empty, being able to be controlled remotely etc.
Intelligent traffic control
Traffic lights with sensors r educes emissions by improving traffic flow etc.
Intelligent car management
Reduces emissions by automatically stopping a car engine when it is stationary etc.
Computer Misuse Act
A law which makes it illegal to: access computer material without permission; access computer material without permission with the intent of committing further offences; modify computer materials without permission
Tracking Cookie
Small files saved on your computer that can be used to track your path through a web site, the time you spend there, what links you click, usually for marketing purposes
Tracking cookie concerns
Can contain personal data that could be accessed by a third party without permission
Denial of Service attack
Cyber attack that involves flooding a web server with a large number of requests
Symptoms of a DoS attack
Website access is slow or website crashes
Effects of a DoS attack
Disruption to users and business
Costs of a DoS attack
Labour fixing fault, lost revenue
Reasons for a DoS attack
Financial, political or personal
Asymmetric encryption
Using a public key and a private key to encrypt and decrypt data
Public key
can be distributed to anyone who wishes to send you a message and is used key to encrypt the data.
Private key
is known only by you and is used to decrypt data created
Digital Signature
is a mechanism that is used to verify that a particular digital document or a message is authentic
Digital Certificate
uses the principles of public key cryptography and it can be used to verify that a particular public key belongs to a certain individual and is issued by a third party
