Computer Basic Components

Computer Organization – the Von Neumann model

Most Computers are based on a model proposed by John Von Neumann in 1946
1. The ‘logical’ units of this model are:
– Stored program
– Central Processing Unit: fetches and executes the program instructions sequentially
– Memory
– Input and Output devices

Computer Hardware components

A typical PC System is made up of:
– System Unit
– Keyboard
– Monitor (VDU)
– Mouse
– Printer
– Modem
– Multimedia Devices

Hardware – The System Unit

1. The central component of the system
2. Houses:
– The Processor: corresponds to the CPU
– Memory: RAM and ROM
– Storage: Hard Disk, Removable Storage devices

The Processor (CPU)

• Types include Intel Pentium series, Celerion, AMD Athlon
• Chip at the heart of the computer- does the calculations
• Speed is very important – measured in megahertz (MHz): the faster the processor the more calculations performed per second.

Memory

• A computer must be able to store its calculations and programs
• Two types of memory: “Volatile” and permanent.
• Measured in bytes
• One byte = eight bits

Random Access Memory (RAM)

• Used by the Computer as the working area
• Holds the working program, the data being processed and the interim results
• Volatile - contents are erased if power is cut
• Can be accessed randomly: can get any piece of data directly.
• Faster than perminant storage
• Not to be confused with ROM (Read-Only Memory)

Storage - Hard Disk

• Permanent Memory - records and stores all programs and data / information magnetically
• Larger than RAM - average 12 - 120GB
• Slower - involves mechanical movement (read/write head, revolving disk)

Other types of Storage

• Floppy Disks
• CD/DVD ROM
• Zip Drive
• Magnetic Tape

Input Devices

• Keyboard
• Mouse: used in conjunction with the GUI (Graphical User Interface), point and click
• Other types of Input Devices:
• – Trackballs
• – Light Pens
• – Touch Screens
• – Tablets

Output Devices

• Monitor: also known as the Visual Display Unit (VDU)
• Printers
• – Laser Printer
• – Inkjet Printer
• – Impact

Software

• Generic name of all programs
• Made up of code interpreted by the hardware
• Written in programming languages - Java, C, C++, Perl
• Two kinds of Software:
• – System
• – Application

System Software

• Concerned with the computer itself: devices, file and storage management, error correction
• Main piece of SS: Operating System (OS)
• OS: the driving program of the computer
• – communicates between all programs and the hardware
• – controls timing and sequence of events
• – manages data to ensure security and integrity
• – Examples: Windows, Mac OS, Unix

Applications Software

• Concerned with the world outside the computer
• Gives the computer its general purpose nature
• Used for the things you want the computer to do
• Common Examples - Word, Excel, Internet Explorer
• Applications can be more specialised: e.g.Architecture package

How Software is made

• Involves a cycle of research, analysis, development and testing
• Systems Analysts - study the business processes and designs the software
• Programmers - develops the software.

Problems with Software

• Software is complex
• Difficult to test comprehensivly
• Can have bugs: these can be trivial or major
• Symptoms of bugs
• – hanging
• – crashes

The Graphical User Interface (GUI)

• Represents all the program / computer resources as icons
• Workspace represented graphically - creates ‘virtual’ documents
• More usable: led to wider use of computers
• Adds to the unique nature of the computer as both a tool and a medium

Do’s and Don’t’s

DO

• give the computer room to breathe
• keep it in a dry place
• dust free
• shut down properly
• keep removable storage away from the screen

DON’T

• block air vents
• eat or drink while using the computer
• expose to extremes of temperature
• just switch off
• move while the computer is in operation

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