CPU Main Memory User Interface Systems Software

Concepts Utility Programs

Input Devices

Processing(CPU/Memory)

OutputDevices

Storage Devices

• Also called CPU, processor or microprocessor

• “Brains” of the computer• Performs all computer

operations

• Where all the input data and results storedoRandom Access Memory (RAM)oRead Only Memory (ROM)

• RAM is volatile = data are lost when computer is turned off

• Read current info and also write new info• Very important in determining capabilities of the

computer system• Stores work when they are in use.

o Word Documento Spreadsheeto Power Point

• ROM is non-volatile = permanent and are not affected where computer is turned lost

• Can read info Stored in ROM

• Can not write new info into ROM

• Used for “internal workings” of computer– Boot Software

• A function of the operating system that allows individuals to access and command the computer

• Command-based User Interface• A particular user interface that requires text commands be

given to the computer to perform basic activities• E.g., unix, DOS

• Graphical User Interface (GUI)• A user interface that uses pictures (icons) and menus

displayed on the screen to send commands to the computer system

• Input Devices -> keyboard, mouse, monitor, touch-screen• Features of GUI -> Windows, Icons, Menus, Pointer

• Hardware Independences• Memory Management• Processing Tasks• Networking Capability• Access to System Resources

and Security• File Management

• Hardware independence– Operating system (OS) provides

hardware independence for application software

– Application software interfaces (API) with the operating system which interfaces with the hardware

• Memory management– Control how memory is accessed and

maximize available memory and storage

• Application Programming Interface (API)• A language and message format used by an

application program to communicate with the operating system or some other control program such as a database management system (DBMS) or communications protocol

Application Program Interface Links Application Software to

the Operating System

• Processing Tasks– Multitasking / Multiprogramming:

• More than one program in RAM at the same time

• Allows more than one active user program to be stored in main memory simultaneously

• Fairly sophisticated• All the jobs that enter the system are

kept in the job pool. This pool consists of all processes residing on mass storage awaiting allocation of main memory.

• If there is not enough room, then the system must choose among the jobs.

• A time-sharing system is a multiprogramming system.

• Processing Tasks– Time-Sharing

• Sharing of a computing resources among many users by means of multiprogramming

• Allowing a large number of users to interact concurrently with a single computer

• Dramatically lowered the cost of providing computing capability

• Made possible for individuals and organizations to use a computer without owning one

• Promoted the interactive use of computers and the development of new interactive applications

• Networking Capability– Features and capabilities of the OS

that aid users in connecting to a computer network

– Allow connected computers to:oCommunicateoShare resourcesoDivide work

• Access to system resources and security– Protection against unauthorized

access– Logins and passwords

• File management– Ensures that files in secondary

storage are available when needed and that they are protected from access by unauthorized users

• Help to perform maintenance or correct problems with a computer system.

• Designed to limited range of tasks• E.g. :

– Hardware utilities, – Virus-detection – Recovery utilities– File-compression utilities, – Spam and pop-up blocker utilities

• CPU is a ‘brain’ of a computer• Main Memory:

– RAM (volatile) & ROM (non-volatile)

• User Interface– Command-based User Interface– Graphical User Interface

• Systems Software Concept:– Hardware Independences– Memory Management– Processing Tasks– Networking Capability– Access to System Resources and Security– File Management