INTRODUCTION TO COMPUTERS AND THE INTERNET

WHAT IS A COMPUTER?
- A programmable machine that carries out what it has been instructed to do.
- It can only do ‘certain’ tasks.
- A Computer is a machine that manipulates data according to a list of instructions.








COMPUTER OPERATIONS
Basic operations that a computer can perform:

•  Input
•  Processing
•  Output
•  Storage

Others:

•  Communication

The five activities above forms the information processing cycle

Information Processing Cycle

• A computer converts data (from input) to become information (as output).
• Processing requires a set of instructions, known as programs or software.
• A computer holds data, instructions and information in storage for future use.
• Data : a collection of unprocessed items such as text, numbers, images, audio and video.
• Information : meaningful and useful facts to people.

COMPUTER COMPONENTS
- Hardware – physical parts
- The electrical, electronic or mechanical parts of a computer.
Includes:

•  Input devices
•  Output devices
•  System unit
•  Storage devices
•  Communication devices
•  Software – the set of instructions / programs

- Also known as a program - a series of related instructions, organized for a common purpose.
- It tells the computer what task to perform and how to do it.
Includes:

•  System software
•  Application software

Others:

• People
• Data / information

Computer Characteristics
Why we can rely on the computer? Because of its …

•  Speed
•  Reliability
•  Consistency
•  Storage
•  Communication
•  Others???

COMPUTER HARDWARE BASICS:

COMPUTER HISTORY, COMPUTER ARCHITECTURE, SIZE PROCESSING POWER AND TYPES OF COMPUTERS

·         Pre computers and Early Computers (before 1940s)
·         Experts concluded that ancient civilizations had the ability to count and compute.
·         Abacus – earliest recorded calculating device.
·         Others: slide ruler, mechanical calculator, Punch card tabulating machine (by Dr. Herman Hollerith, 1890s) and Sorter
·         Hollerith’s company eventually became IBM (International Business Machine)

First Generation (1940 – 1950) :: Vacuum Tube

·         ENIAC (1945): Designed by Mauchy & Echert, built by US army to calculate trajectories for ballistic shells during Worlds War II. Around 18000 vacuum tubes and 1500 relays were used to build ENIAC, and it was programmed by manually setting switches.
·         UNIVAC (1950): the first commercial computer
·         John Von Neumann architecture: goldstone and Von Neumann took the ideal of ENIAC and developed concept of storing a program in the memory. Known as the Von Neumann’s architecture and has been the basis for virtually every machine designed since then.

Features:

-          Electron emitting devices

-          Data and programs are stored in a single read0write memory

-          Memory contents are addressable by location, regardless of the content itself

-          Machine language/Assemble language

-          Sequential execution

Second Generation (1950 – 1964) :: Transistors

·         William Shockley, John Bardeen, and Walter Brattain invent the transistor that reduce size of computers and improve reliability. Vacuum \tubes have been replaced by transistors.

·         First operating Systems: handled one program at a time

·         On-off switches controlled by electronically.

·         High level languages (COBOL and FORTRAN)

·         Floating point arithmetic

Third generation (1964 – 1974) :: Integrated Circuits (IC)

·         Microprocessor chips combine thousands of transistors, entire circuit on one computer chip.
·         Semiconductor memory
·         Multiple computer models with different performance characteristics
·         The size of computers has been reduced drastically.

Fourth Generation (1974 – Present) :: VLSI / ULSI

·         VLSI = Very large-Scale Integration
·         ULSI = Ultra Large Scale Integration
·         Combines millions of transistors
·         Single-chip processor and the single-board computer emerged
·         Creation of the personal computer (PC)
·         Use of data communication
·         Massively parallel machine

Fifth Generation (now and the future)

·         Based on artificial intelligence – computers can think reason and learn
·         Primary means of input – voice and touch
·         Different computers construct such as optical computers that utilizes nanotechnology, or as entire general purpose computers

SOFTWARE

WHAT IS SOFTWARE

• The intangible part of a computer.
• It tells what a computer supposed to carry out, and how to do it.
• It drives the hardware.
• A collection of computer programs together with the related data.

CATEGORIES OF SOFTWARE

• Software is divided into three categories:
•                 System software
•                 Application software
•                 Programming software
• System software- controls and maintains the operations of the computer and its devices.
• Application software – makes users more productive and assists them with their tasks.
• Programming language – enables people (called programmers) to communicate instructions to a computer.

HOW DOES COMPUTER KNOW WHAT TO DO?

• It must be given a detailed list of instructions, called a computer program or software that tells it exactly what to do.
• Before processing a specific job, the computer program corresponding to that job must be stored in memory.
• Once the program is stored in memory the computer can start the operation by executing the program instructions one after the other. 

SOFTWARE LAYERS

OPERATING SYSTEM

• OS receives order from the user via application program
• It has programs and routines that control all accesses to hardware
• Higher levels are protected from any issues

Multiple users

Multiple requests for the same resource

Access control

• When the OS determines it’s safe to proceed, direct calls to device drivers are performed

DEVICES DRIVERS

• Device drivers are very low level instructions to a device (e.g., the printer, or the hard drive)
• It can provide interface or communications directly with hardware devices.
• It also allows OS to directly access hardware resources
• Drivers are hardware-dependent and OS-specific

SYSTEM SOFTWARE

The part that typically involved is the BIOS – Basic Input Output System. It provides a small library of basic input/output functions used to operate and control the peripheral devices.
It supports common activities that high level applications need to do, e.g., printing.
Contains library routines and common tools that hide operating system from applications.