Computers Flashcards
What is Vonn Neumann architecture/Stored program concept
Programs stored inside the computer that can be reprogrammed.
CPU
Carries out program instructions and it does this using the FDE cycle.
Processing unit
- an arithmetic logic unit
- processor registers
Control unit
Receives signals from other parts of the computer system and sends signals to them,
RAM
- Random Access Memory - Used to store data and machine code currently being used
- Volatile - data lost when turned off
- Stores programs and instructions.
- Read and Write
- 1-256GB
ROM
Read-Only Memory
* Stores important system information and boot code.
* Volatile.
* 6-8MB
Cache
High-speed memory used to store frequently accessed data or instructions. Located closer to the CPU than the main memory, allowing for faster access times and improving system performance
Stores frequently accessed data, e.g. A font, a texture pack
FDE
Fetch
Decode
Execute
Fetch
- the CPU fetches data and instructions from the RAM and saves it in its very short memory, called register.
- CPU uses the address bus. the memory address of the next item that the CPU wants is put on the address bus.data from this memory address travels from the RAM on another bus called the data bus.
Decode
CPU working out what the instructions that it has just fetched actually mean.
Execute
when the data processing happens
instructions are carried out on the data. some instructions are carried out by the ALU (adding, shifting, AND, OR)
Contents of the CPU
- an instruction register
- a program counter
- memory that stores data + instructions
- external data storage
- input and output date
What is a computer
- Anti malware
- Encryption
- Acceptable use policies
- Backup
- Recovery procedures
Embedded system
An embedded system is a computer that has a specific function and does not do anything else
Small storage device to store simple programs, as it relies on fixed inputs and outputs. It needs no software updates.
Uses of an embedded system
A traffic light
Switch lights, keep track of time, recieve input from pedestrian button, recieve input from road sensors
Characteristics of an embedded system
- Task specific (single purpose)
- Low power consumption
- Small physical size
- Low maintenance
- Low cost per unit
- Less storage
- Limited user interface
Purposes of an OS
Software that manages a computer’s hardware and software resources and providing common services for computer programs
Provides easy-to-use GUI (graphical user interface)
Functionality of an OS
Input and output from peripherals
Providing user interface
File management
Program management
Memory management
Processor management
Running applications
Ensuring security
Error handling
Utility software
- File repair
- Backup
- Data compression
- Defragmentation
Backup
Antivirus
Firewall
App update mangement
Formatting disks and drives
System analyis tools
Characteristics of a general purpose computer
- Non task specific
- High power consumption
- Often large
- High cost
Methods of identifying vulnerabilities
Audit trails
Code reviews
ALU
Performs actual operations on data, arithmetic or relational.
Registers
extremely fast memory. located on the processor, and very very small. (Bytes)
Faster than RAM as no buses needed
Clock
determines the speed of the CPU.
the chip uses a vibrating quartz crystal that maintains a constant rate of vibration.
Instruction register
holds instructions executed by CPU
Accumulator
holds ALU vales
Program counter
holds the memory address of the next instruction to be fetched
Bus
A thin wire used to connect computer components and transfer data between them
Data bus
Carries binary data from component to component
Bidirectional
Control bus
Carries signals that control CPU components
Birdirectional
Address bus
Carries the address of a memory location
Unidirectional
Interpreter
Transfers from high level to machine code line-by-line as the program runs
Compiler
Translates from high level to machine code before the program runs
High level programming languages
Easier for humans to use as the language is closer to English
* - Abstracted away from hardware
* - Uses English-like statements
* - Requires a translator to convert source code to machine code
* - Python, HTML, Java, C++
Microprocessors
Each microprocessor with a unique set of components requires a different unique set of instructions. For each allowable and defined behaviour, there is an abstract instruction.
Low level programming languages
Assembly and machine code are the only two low-level programming languages.
- Sits close to hardware
- Consists of mnemonics that represent binary code
Machine code
Binary patterns representing a program
* Simple for CPU to execute, difficult for humans to understand
* Not portable - each microprocessor requires a different set of instructions
Assembly code
One line of assembly code is one instruction
Easier to understand than binary, as the mnemonics are similar to English.
Secondary storage
**Stores data for long periods of time. **
* Easy portability
* Faster read speeds
* Greater durability
Magnetic
** Large moving parts**
* Series of polarised dots
* Large capacity
* Inexpensive
* Lifespan until dots aren’t polarised and cannot be read
Optical
Uses lasers to heat/burn pits and lands into a reflective surface that represents 1s and 0s -> binary code
* Moving parts
* Small capacity
* Cheap
* Lifespan until information cannot be read
Solid state
- If a row of transistors are charged, this represents a 1
- If a row of transistors is uncharged, this represents a 0
- Arranged in a gird
- At row/column intersections, two transistors create a cell (control gate and floating gate)
- Applying voltage to the control gate transistors causes electrons to flow onto the floating gate
- Creates a net positive charge that interrupts current flow
