(6) Computer Systems

System Software, Application Software

Operating System, Utility Programs, Library Programs, Programming Translators

Bespoke Software- made for a custom tasks Generic off the shelf software-Designed to complete a broad range of tasks Special Purpose (ready made)-Made for one particular task

A program that designed to hide the complexities of hardware from the user. Manages the operations of the computer for the user, acts as a bridge between the user and computers hardware. Eg. Windows, MacOS, iOS Function • Moving data into and out of Ram • Allocate I/O devices to processes • Decides which process to carry out • Disk fragmentation Allocate processors/cores to processes // schedule processes // decide which process to carry out when; Allocate memory/RAM to processes // moving data into and out of RAM / to a paging file for virtual memory // ensuring processes can only write to memory that they have been allocated; Allocate I/O devices to processes // manages communication between processes and I/O devices // automatic installation of drivers for new I/O devices; A. examples of devices NE. manages I/O devices Allocate space on a storage device to files // organising files into directories // determines where on a device to save a file // recognising storage devices when they are connected; A. defragmentation of disks NE. saving a file Installation of new software // automatic/managing updating of software; A. “programs” or “tasks” for “processes” R. handling interrupts R. hides complexity Note: Students must describe the type of resource management – phrases such as “processor management”, “allocating memory” etc are not enough.

Small programs with one specific purpose that is designed to optimise the performance of the computer. • Disk Defragmenter • Virus Checker • Backing up files • compressing or decompressing data • encrypting data • providing a firewall

Ready compiled programs which can be run when needed. -Maths calculations

Converts program code by a programmer into machine code which can be run by the computer -Compilers, Interpreter, Assembly

• Software that is needed to run the computers hardware and application programs • Software that performs tasks to run computer; • Layer of software which enables user to operate computer; • Software that hides complexity of computer from user/provides virtual machine; • Software that lets user communicate with/manage hardware; • Software to run applications/hardware/programs/computer/ packages; • Software required to make computer work;-

Software that carries out tasks that the user is interested in doing such as writing a letter, creating graphs, sending an email or downloading a webpage. Performs tasks for the user

Hardware is all the physical components that make up a computer Software is the programs that run on a computer

It manages how much RAM a program has access to which allows multiple applications to run simultaneously.

Involves deciding what order to execute each instruction in. Only executes one instruction at a time

The OS uses device drivers to communicate with I/O devices connected to the computer system.

(Low Level) Machine Code - A line of code (1’s & 0’s) split into opcode and operand

(Low Level) Assembly Language - The opcode is mnemonics and the operand is decimal/ hexadecimal

(Both High Level) High level language - E.g. C#, Java etc Declarative Language - You state what you want, not how to do it

+Relatively easy to learn +Easier and quicker to write in high level language +Capable of running on multiple different computers -Requires a compiler to run

Compiler, Interpreter, Assembler

• A compiler produces object code whilst an interpreter does not • A compiler translates the whole of the source code into object code whilst an interpreter translates line by line -The object code produced by a compiler will execute faster, (once it is compiled) than interpreting the source code (every time the program is run) -An interpreter can run (syntactically correct) parts of a program whilst there are syntax errors in other parts of it, which a compiler cannot;

Source code goes in; object code comes out

It converts low level language into the correct machine code

• Object code executes faster than interpreted code - Object code is more secure as it cannot be read

Compiler -Games/ Movies - Interpreter -To debug code -