Range
The more bits/figures in the exponent, the bigger the range
Finding the range
The range for any number of bits is -2^(no. bits -1) to 2^(no. bits -1) -1
Precision
The more bits/figures in the mantissa, the more precision (/accuracy)
ASCII
ASCII characters take up 8 bits (1 byte)
Advantages of ASCII:
* small file size
* uploads and downloads faster
Disadvantages:
* limited number of characters (256)
Unicode
Unicore characters take up 16 bits or 2 bytes
Advantages of Unicode:
* Multiple languages
* 65k characters
Disadvantages:
* larger file size
* uploads and downloads slower
Fetch-execute cycle (f-e)
While a program is running, buses are used to locate and then carry each program instruction from the memory to the processor where it is decoded and executed.
The fetch-execute cycle follows the steps below:
1. The memory address of the next instruction to be fetched is placed on the address bus.
2. The read line of the control bus is activated by the control unit.
3. The instruction is located at the memory address specified by the address bus. The instruction is then sent along the data bus to the processor.
4. The instruction is then decoded and executed by the processor.
Factors affecting computer system performance
Number of processors (cores):
* Affects how many instructions can be executed concurrently
Width of data bus:
* Affects the number of bits/data transferred in a single operation/reduces number of fetch operations
Cache memory:
* Affects the number of fetches/accesses from slower main memory
Clock speed:
* Affects the number of instructions executed/carried out per second
Projects - Scope
A list of what will be delivered to the client or end-user at the conclusion of the project + the time-scale in which the project will be carried out. client may expect to receive a report on the test plan, the results of the testing and an evaluation report.
Projects - Purpose
Describes the reason for creating new software
The needs of the end-user or target audience will become the purpose of creating the software.
helps inform further analysis and design.
Projects - Boundaries
A list of what will and won’t be included in the project.
Without boundaries, the developer and client may disagree
If the client asks for additional functionality during the project, the developer may request additional payment to implement the new features.
Projects - Functional Requirements
Outlines the project in terms of inputs, processes and outputs. The processes may be listed as the different functions performed by the software.
Bit-mapped graphics
Stored as a grid of pixels, each with a unique 8-bit color code.
* Storage requirements determined by resolution and color depth, usually large
* Allows editing of individual pixels
* No layering
* resolution cannot be increased without pixelation / loss of image quality
* uses .bmp, .jpg, .png
Vector graphics
Stored as shapes with a list of attributes
* File size generally smaller than bitmap
* Shapes can be edited
* Shapes have layers, can be position in front/behind others
* Resolution dependent on the device drawing them. Can be scaled up and down without loss in quality
* commonly uses .svg
Environmental impact - Heating systems
- can respond to external weather conditions
- can adjust heating based on historical patterns of data
- can be remotely controlled when not home
- real time temperature monitoring through mobile devices can reduce unnecessary fuel use
Environmental impact - Traffic control
Traffic management systems are designed to keep vehicles moving and optimise traffic flow. Vehicles which are moving rather than idling, put out less emissions
Environmental impact - Car management systems
Engine management systems take readings from sensors in the engine to improve engine efficiency and reduce fuel consumption
Security risks - Computer Misuse Act
(1990): it is illegal to:
1. Gain unauthorised access to computer material
2. Gain access with the intent to commit a further offence (eg blackmail)
3. Modify data or programs on a computer system without authorisation
Access, Intent, Modification (AIM)
Security risks - Tracking cookies
- Tracking cookies allow third parties to follow the browsing history of the user
- This may disclose activity which the user wishes to keep private or may allow profiling of the use eg for personalised advertising
Security risks - Denial of Service (DOS) attacks
DOS attacks aim to prevent users form accessing a computer system/network by flooding the system with bad requests.
* Consumes bandwith
* Starves the computer system of resources (eg memory)
* Causes loss of revenue due to users not being able to access websites, and costs money to repair systems
Encryption
Pairs of encryption keys - public and private - are used to scramble data so effectively that it cannot be read by unauthorised users. A public key is known by everyone and is used to encrypt data. A private key is known only to the recipient and is used to decrypt data.
Digital certificates
- authenticates a person
- issued only by trusted entities / certification authority
- shows that person / site is regulated and up to standards
Digital signatures
- authenticates the sender
- guarantees the integrity of the sent item - sent item has not been altered
