Computer Systems <3 Flashcards
How to calculate range of positive integers
2^n -1
How to calculate range of Two’s complement numbers
2^n -1 (÷2)
What is a real number ?
A real number is a number with a decimal point. A real number can be positive or negative.
Disadvantage of ASCII
they only used one byte they were limited to 256 characters
Advantage of UniCode
- All current and historic languages can be represented and understood by all modern computing devices;
- The first 128 characters are identical to ASCII which maintains backwards compatibility with older files.
Disdvantage of UniCode
- UniCode takes up much more storage space than ASCII
- The UniCode standard only defines what each number means and leaves it to software developers to decide precisely how each character looks on their system.
Bitmap
A bitmap is a representation of a graphic using a grid of bits to store the information about the colour of each pixel in an image. Bitmapped images appear as pixels.
Bitmap colours
When using colours, multiple bits are stored for each pixel. The more bits user per pixel, the more colours can be stored.
Vector
Stores them as a description of the shapes in the image to enable them to be re-drawn for recreating that image rather than storing them as individual pixels.
CPU meaning
Central Processing Unit
What is a bus
Buses are the lines which connect the CPU to the main memory.
Address bus
The address bus is a unidirectional (1 way) bus
Data bus
Data bus is a bi-directional (2 way) bus
When data is read from or written to memory STEPS
the processor sets up the address register with the address of the memory location to be accessed,
the processor activates the read or write line on the control bus,
and data is then transferred to or from the data register via the data bus,
Memory location address
Activates read/write line
Data is transferred
How to calculate memory locations
2^n - n being number of lines
16 lines = 2^16 possible memory locations;
STEPS to execute n that (computer systems)
Transfer the contents of the Program Counter to Memory Address Register
Increment the Program Counter
Activate Read line (thereby transferring instruction to the data register)
Transfer contents of data register to the instruction register ready for decoding
Decode Instruction
Execute Instruction
What is an intelligent system
A computer system that would need some level of human-like intelligence to run :)
Heating Systems Examples
Smart thermostats
Smart heating systems
Activicty sensors
Traffic Control Examples
Intelligent transport systems
Navigational Systems
Car Management Systems Examples
Start-stop systems
GPS sensors
Engine Control Units
Law for computer misue
The computer misuse act 1990
Tracking cookies use
To get adverts you actually want
What is a DOS attack
A Denial of Service (DOS) attack is when a website or a network is targeted, with the intention of making it unavailable to users.
What is encryption
Encryption means that before information is sent or stored electronically, (for example in an email), it is scrambled using a mathematical process which turns it into something that looks like nonsense.
This means that if anyone steals the information it will be meaningless to them. It will look like gobbledygook.
What is a digital certificate
A digital certificate is an electronic document that contains a digital signature, which confirms the name and identity of a person or organisation.
What is a digital signature
A digital signature is an electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a document, and to ensure that the original content of the message or document has not been tampered with.
