Second year test Flashcards
What is normalisation?
Every attribute is dependent upon the key, the whole key and nothing but the key
What is 1st normal form?
Stops repeated groups
What is 2nd normal form?
Partial key dependence test
What is 3rd normal form?
non-key dependence test
Why is normalisation important?
reduces data duplication
eliminates data inconsistency
What SQL commands are there?
Select From Where Order By And Insert Into Update Delete from Create
What is record locking?
A technique to prevent updates being lost or inconsistencies in data rising. Database is locked until table has been edited and updated.
What is underflow?
When number is too close to 0 to be represented
What is overflow?
a number is too big to be represented in a given number of bits
What is cancellation error?
When a sum is between two numbers of a very different size
What is a recursive route?
A route that is defined in terms of itself
What is an intractable problem?
Can be solved by a computer, but cannot be solved in a reasonable time for large inputs. Anything less than O(n^2)
Example or logarithmic time
Binary search
Example of Linear time search
Linear search
Example of quadratic time search
Bubble sort
Example of exponential time search
Fibonacci algorithm
example of Factorial time
travelling salesman problem
What is serial data transmission?
Data is sent, one bit at a time, across a single wire
What is parallel data a transmission?
Several bits are sent simultaneously over a number of parallel wires. Short distances.
Why is serial better for longer distances?
In parallel, interference(skew) can occur at high frequencies
What is the baud rate?
the rate at which the signal changes?
What is the bit rate of a channel?
(baud rate)x(number of bits per signal)
What is bandwidth?
The range of signal frequencies that a medium can transmit. The greater the bandwidth, the greater the potential bit rate.
What is latency?
The time delay when a component is responding to an instrument
What is the purpose of a parity bit?
To detect errors in code
What is a protocol?
A set of rules relating to communication between devices
What is Asynchronous transmission?
A transmission which only synchronises for the duration of the transmission by sending start and stops bits
What is a LAN?
A number of computing devices connected by cables. Sends data very fast over a short distance
Advantages and disadvantages of a bus topology
Advantages) Less cable and doesn’t require additional hardware
Well suited to small networks, low speed
Disadvantages) If main cables fails, whole network goes down
Limited cable length and amount of stations
Performs degrades with heavy traffic
Low security, all computers on network can see transmissions
What is the fetch execute cycle symbols?
MAR
