components of a computer system
- hardware: physical components
- software: instructions + programs which control the hardware
- procedures: modes of action performed by personnel
- personnel: people involved in using system
- data: raw info, input
the function + operation of hardware within a computer system
input –> processing + control <–> storage <–> processing + control –> output
basic functions of input - refer to hardware deck
- obtains data from outside the system through an action
- input converted to binary signal
- e.g. keyboard, mouse, barcode reader, microphone(sound card), RFID
how is input received by the processor
- input from user is converted into a binary signal
- signal sent to buffer, a circuit that is part of the RAM
- RAM allows devices operating at different speeds to communicate
- signal accessed by processor
basic functions of output - refer to output devices deck
- sends data outside the system, via a port
- data is sent from processor to output device through buffer area
- e.g. video cards, hardcopy devices, internet, actuators(similar in function to motor neuron in the body)
main function of storage
instructions and programs that control hardware
- reads, writes and retains data
- classified as primary and secondary, or temporary and permanent
primary vs secondary storage: refer to storage units deck
primary(temporary): main memory, requires power to retain data
- volatile(except for ROM)
- fast, small, expensive, close to CPU
- works closely with processor
secondary(permanent): permanent, does not require power to retain data
- non-volatile
- mostly classified as magnetic, optical or solid
- slow, big, cheap
- greater storage capacity
conceptual diagram of software linking with hardware
users <–> application software <–> operating system <–> hardware
function of operating systems
- organises + controls hardware
- allows application software to interact with the hardware
- provides interface to hardware, user, software applications
types of operating systems users + tasks
Single-user, single-task systems
- one user, one task
Single-user, multi-tasking systems
- multiple programs on a single computer, common in personal computers
- operating system allocates CPU time to each program
Multi-user operating system
- separate resources, multiple users allowed access at one time
- used in mini + mainframe computers
RTOS: real time operating systems
- machinery + specific instruments, fast w/ no lag
- tasks performed in real time/instantly
tasks performed by operating systems
processor Management
- allocates background processes their processing time
memory + storage management
- allocates memory for separate processes, avoids clashes
device management
- translates the program into appropriate language for device
application interface
- provides communication between application + operating system
user interface
- provides communication with user
software utilities
- file compression: saves storage, reduces file size
- defragmentation: rewrites drive to present file fragmentation for better performance
- virus checking: packages which scan executable code in search of code that could cause unwanted processing
- embedded license installation: ensures compliance with software license Ts + Cs
- batch job scheduling: regular tasks scheduled for no-user times
- emulators: allows old software to operate on other/newer operating systems
application software meaning
software which is created in response to a problem, sitting on top of the operating system
- application software is designed with a specific operating system in mind
difference between off-the-shelf packages + custom designed packages
off-the-shelf packages
- distributes through internet or retail stores
- the wider the audience, the cheaper the product
- could be used as a software development tool; which will create CTOS(customized off the shelf) packages, which will require the original product to operate
custom designed packages
- customized to client’s unique problem
- usually made for large businesses/the government
- apps with unusual/custom hardware
- performance decreases with more users
machine languages
- understood by CPU
- lowest level of code
- hard to understand
- represented by a series of binary digits
- other languages are translated into this eventually
assembler languages
- mnemonics used
- more english-oriented than its predecessor
- simple translation into machine code
- optimised for speed
high-level languages
- for complex solutions
- translator needed, for a specific CPU
- more easily understood by programmers
- very long timeline of evolving high-level languages
- clearer instructions + syntax, usually in english
declarative languages
- order of statements have no significance
- specifies aspects of the problem
- solution formulated by software/other functioning systems
- similar to spreadsheets, other data-based queries
event driven vs sequential
event driven: each control is constantly monitored for an input
- collection of inter-related modules when input is received, corresponding code is executed
- multiple events can happen at the same time
- lots of controls used
sequential: pre-determined sequence
- unable to deviate from sequence
- not flexible, does not account for user’s possible input
steps of translation
- lexical analysis: ensures program is a legitimate part of the language
- syntactical analysis: ensures the syntax is correct
- code generation: generation of the machine code from o.g. code
compilation vs interpretation
compilation: translates the whole of the source code at once
- only needs to be translated once on one local source
- very fast, no translation needed during run time
interpretation: translates source code statement by statement
- translates code at run time
- significant processing = poor performance
- good for testing small changes to code
- interpreter must also be installed
fetch-execute cycle
a cycle used to carry out each and every machine language translation
- information hardwired in CPU
microcode
CPU operations which machine language instruction corresponds to
two parts of fetch execute cycle
- instruction time(I-time): involves fetching the instruction from memory and then decoding it
- execution time(e-time): involves executing instruction and storing the result
