Systems, Architecture, CPU

Hardware

the physical components that make up a computer system

Software

The non-physical programs that are stored by and executed on a computer system, controlling the operation of the hardware components

System software

A software that controls the computer so it can function, managing the hardware and providing a platform for other software
(eg: utility software, operating system, library routines, programming language translators)

Application Software

A software for end-user tasks on a computer

(eg: word processor, spreadsheet, presentation software, a computer game, databases, payroll, accounts, air traffic control)

Embedded System + Non-embedded

computer built into other devices 

(often to control system, monitor machinery dedicated to a single task; usually easier to design; cheaper to produce; more efficient; generally have more ROM than RAM as don't write much to memory; don't tend to have secondary storage so ROM used to store all programs; ROM + RAM often on same chip to reduce space + cost)

eg: dishwashers, microwaves, TVs, lifts/elevators, traffic lights, fridges, vending machines

Non-embedded systems -> more RAM than ROM cause need to write data often to main memory; ROM typically only used BIOS (doesn't need much mem); ROM + RAM usually stored on motherboard away from the CPU

Operating System + Functions

manages the computer's hardware

Processor Management: allocates how much memory + CPU time is gvien for each process; schedules to determine most efficient order for CPU to execute instruction -> each process allocated priority; may interrupt CPU for process of higher-priority if available; allows multitaksing CPU swaps between diff processes very rapidly

 Application Management: provides platform for applications to run on; OS runs a program to install it + interact with applications through on API (Appilications Program Interface) allowing to communicate with OS + allocate space in ememory for it to be loaded multitasking (allowing multiple to run at once), allows application to access hardware + other peripheral devices needed (inc RAM + secondary storage)

Security Management: ensures safety from threats/attacks with (control access rights (can't access if aren't system administrator) + privileges, setting logins + passwords/ biometrics, automatic updates downloads for OS to ensure security loopholes are patched; encrypting files stored on the hard disk); may have anti-theft measure to prevent info stolen;

user account control access; can't access others personal data lest a system administrator; may have anti-theft measure to prevent steal info

Memory Management: allocates memory for any  data file + frees up space for reused when application opened; OS copies necessary part to memory; OS decides if applications/features have been recently used (if not, may remove from memory); manages how much RAM a program gets access to depending on program; when running multiple apps at once; OS makes sure doesn't overwrite or interfere with each other

Input/Output (I/O) device management: communicating with device drivers, which act as an interface between the device + computer, OS will stall new matching drivers for devices

File/storage management: responsible for organising data into usable heirarchical structure + moving/editing/deletion of data; manages hard disk + splits into sotrage sectors; decides which sector to write data on; keeps track of free space + maintaining utility programs like defrag software; system cleaup (rid of temporary files taking space); compression so less disk space; backups (copy files; setting stored externalling); encryption (scrambles data to stop third parties accessing; decrypted only with a key); virus scanners (inspect each file with list of known viruses to check for + updated regularly)

 Network management

CPU

processes all data/instructions

To improve CPU performance:

1. Increase the clock speed (determines no. instructions a single processor core can carry out per second)

2. Increase the number of processor cores (each core can process data independently so more core, more instructions can be carried out at once)

3. Increase the cache size

4. Change the type of cache memory (eg: L3 to L1)

Overclocking = setting the clock speed higer than factory-set rate but can make CPU overheat, could cause crashes or permanent damage

Control Unit

decodes and coordinates the execution of instructions

(and sends control signals to other components; controls transfer of instructions through the CPU; coordinates + controls all the activities within the CPU; controls flow of data within + outside CPU)

ALU

 completes all calculations and logic operations

Clock = sends a regular electrical pulse to control timing of the processor and synchronise the operations of the CPU (influences no. instructions carried out each second) -> number of clock cycles per seond = clock speed

Registers

memory locations in CPU which store small amounts of data and intermediate, needed results when performing operations (holds data when executing an instruction/ holds a memory address/ holds an instruction)

Cache

very fast memory, makes retrieving data + instructions from hte computer's memory more efficient (slower than register but faster than RAM; frequent used data stored for faster access in near future; when CPU requests data, checks cache first; very low capacity; very expensive; speed depends on how far away from CPU)

Buses

 collection of wires used to transmit data between components (processors may have separate buses for carrying data)

RAM

main memory; volatile (requires power); can be read/written to; hold OS while on; slower than cache but faster than secondary storage

ROM

main-memory; non-volatile; only read not written; chip built into motherboard; contains BIOS (Basic input ouput system)

Non-volatile memory

retains data when power is lost

Why does a computer tend to have more RAM than cache?

- RAM is cheaper per byte

- Typically the capacity of cache memory is not enough to store both data and programs

What does more RAM mean?

more applications/ more memory-intensive applications can smoothly run/ faster, but if already a lot, makes no diff if surplus

Von Neumann architecture

 system where CPU runs programs stored in memory; program consists of instructions and data, both stored in memory addresses

FDE CYCLE

Fetch: program's next instruction fetched from RAM where it's stored and brought to CPU, program counter increments to hold the address of the instruction

Decode: the control unit decodes and interprets the instruction

Execute: CPU tells relevant components to execute the instruction, may involved an arithmetic/logical operation, storing/loading data from/in main memory