Software definitions

mreow

Software

A set of programs/instructions written in a programming language performing 1 or more tasks to tell the computer what to do. It allows the computer to function.

Hardware

The physical and peripheral components of a computer.

Firmware

A software permanently stored on the hardware/ROM which contains instructions allowing the hardware to function and communicate with software.

Bootloader

A small piece of firmware containing the instructions to start up the operating system; it loads the OS onto the RAM upon startup.

How do applications access hardware resources?

Through making 'calls' to the OS and the device drivers.

System software

The manager: A variety of programs which are necessary for the computer to function and manages the operation of computer hardware and software.

Application software

The software which the user needs to perform specific tasks using the computer's resources.

Operating system

The platform in which other programs/applications are run on. Also provides the user with a human computer interface.
- Allocates the hardware's resources

Utility Software (MMC)

Manages, maintains, and controls the computer's resources. It makes sure everything runs smoothly.

Interrupts

A signal sent from a device or a software to the OS which causes a temporary stop in the current instruction being processed to service the interrupt.

What are interrupts sent through?

Interrupt Request Lines (IRQ)

What are interrupts sent to?

The interrupt handler in the OS to perform the Interrupt Service Routine (ISR)

Examples of Interrupts

- Dividing by 0
- Hardware faults like no paper in printer
- Hardware interrupts like keyboard presses

High Level Language (HLL)

Programming language written in a language (like English) that humans understand. It is a portable language which can be used on multiple platforms (machine independent).

Low-Level Language (LLL)

Programs written for a specific type of architecture and hardware. It is non-portable and machine dependent.

Advantages and Disadvantages

* Debug ease
* Hardware (directly manipulates or machine independent)
* Ease of writing/understanding
* Memory space taken up (1 line = 1 machine or many lines of abstraction?)
* Speed of execution

Assembly language

A low-level language, it uses mnemonics to specifically manipulate hardware. 1 line of assembly language translates to 1 line of machine code.

* Difficult to debug
* Mnemonics
* Directly manipulates hardware

Ex. Bootstrap in ROM

Assembler

Translates assembly language into machine code. Assembly language generally takes up less memory space than high level languages.

Advantages of Assembly language

* Uses less space in memory
* Faster processing speed
* Therefore is more efficient overall
* Directly manipulates hardware

What is a compiler?

A compiler is a software program that translates source code written in a high-level programming language into machine code that can be executed directly by a computer.

* Compiles and translates the entire file at once
* Produces an executable file specific to computer architecture
* If a syntax error is encountered, the compiler doesn’t produce an executable file, and sends out an error report

What is an interpreter?

A software program which translates high-level language into machine code line-by-line

* If a syntax error is encountered, it stops translating at that line and sends out an error report
* Code must be retranslated each time it is run

Advantages of a compiler

* Produces an executable file, so users can’t see or edit the source code for stealing
* Only needs to be translated once, so it’s faster to run
* User doesn’t need to have interpreter installed to execute the code

Advantages of an interpreter

* Faster and easier to debug during the development process, as users can clearly see where the error was made

Integrated development environment (IDE)

A program which allows users to write, debug, and translate code

Consists of: Prettyprint, Run-time environments, Code editors, Autocomplete and autocorrect, Translators, and Error Diagnostics

Code editors

Used to write and edit program code

* Makes the code clearer, to make editing easier for programmers
* Prettyprint, Syntax highlighting, Indentation, Line numbers, Autocorrect and complete

Run-time environments

The facility of the IDE which runs programs

* Allows users to test code
* Gives useful reports as to errors or program crashes

Prettyprint

Applying formatting and indentation to make the code easier to read

Error Diagnostics

A list of errors and their line numbers reported after testing

* Helps find mistakes made by the programmer. 
* Errors are identified along with the line number.
* The code may be underlined or highlighted.

Auto correct

Replaces/corrects any grammatical errors or variable names which have minor typing errors

Autocomplete

Provides a drop down list of variables/possible choices to complete keywords/variables

Translators

Allows the user to run the code using compilers and interpreters

What does the system software do?

* Helps maintain **good working order** of the computer so it runs **without problems**.
* Provides a platform to run other software. 
* Controls **allocation and usage of hardware resources**. 

Provides a **Human Computer interface (HCI)**