A brief history of the computer was covered in the introduction to the digital practice section of this portfolio. It was concluded within this introduction that any machine that imitated a universal Turing machine could be considered a computer.
The modern desktop computer has developed out of the use of logic gates that can be used to manipulate data. All modern computational devices are a combination of just three basic logic gates, and, or, not.
| And | Or | Not | |||||||
|---|---|---|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | ||
| 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | ||
| 1 | 0 | 0 | 1 | 0 | 1 | ||||
| 1 | 1 | 1 | 1 | 1 | 1 |
Figure 1.
The realisation of these gates using transistors and then integrated circuits has lead to the size of the computer being reduced and the performance of such devices improve greatly.
A basic computer is made up of the following devices:
CPU – The brains of the PC is its CPU. It is here that the most basic instructions for the movement of manipulation of data within the memory exist. This instruction set is called machine code and in many ways is the heart of any programming language. This shall be looked at in more detail later.
PCI cards – PCI cards allow a user to add functionality to a computer without replacing the entire hard disk. PCI cards exist to help improve graphics, allow for network communications or to allow for processing and output of sound. These cards are the Graphics, Network and Sound cards respectively.
RAM – Random Access Memory is volatile memory that exists only while a power source is available to the chip. Turing represented memory as paper sheets. Memory is designed to act like this. If you write something on a piece of paper it is recorded, if you use an eraser to remove this information it is lost and can be written over once again. RAM allows for quick access to any data it contains. Such data includes the operating system which is a loaded into memory on start up. Other applications programs are loaded into memory as required.
ROM – Read Only Memory is stable memory that constantly exists and cannot, unless in very specific cases be overwritten. A ROM chip is used within a PC to store the BIOS. BIOS stands for basic input output system. The BIOS determines what a computer is capable of without accessing any data stored on disk.
Chipset – The chipset is a collection of integrated circuits that are designed to perform one or more related functions. Modern chipsets can perform many different functions that in the past would have required multiple chips. Such functions include communicating with peripherals and disk drives taking in data, and passing it to where it is needed within the machine, and also sending data to such devices where necessary.
Disk Drives – There are various different disk drives available. A hard disk drive is a magnetic storage facility that is capable of storing large amounts of data and accessing such data at high speeds. A floppy disk drive is a magnetic storage facility but with limited capacity and storage and retrieval speeds. More disk drives exist in the form of DVD and CD-ROM drives.
Peripherals – Peripherals include the keyboard, mouse and printers. Peripherals allow the user to interact with the computer and also allow the user to print data from the computer into some physical form such as paper.
USB / Parallel Port – Peripheral devices can be connected to a PC through different ports. Two types are Parallel and USB. Parallel ports allow the communication of parallel pieces of information, i.e. more than one bit of information at a time. USB stands for universal serial bus and uses standardised connections; handshaking procedures and data transfer rates to allow for plug and play connection to peripherals and other devices.
These devices all sit on top of a motherboard. The motherboard is a central circuit board that contains the connectors required to connect these devices and to facilitate communication between them. The devices are all controlled, store and transmit data using various bus types.
Address Bus – The address bus stores information about where data can be found.
Control Bus – Synchronises events within devices and carries back signals
Data Bus – Transports data to and from the CPU, RAM or input / output devices.
Computers exist all around us in various forms. A microcontroller for example exists within programmable washing machines, digital television boxes etc. They have existed within devices such as toasters since the early 80’s. Microcontrollers are dedicated specifically to a single task; this means they have limited capability, and may or may not be true computers. However as hardware is increasingly improved and reduced in size new developments are coming into existence which could in theory put an entire computer into the palm of our hand.
The most recent development in MP3 players for example consist of a hard disk drive, memory, CPU, sound card capabilities, an operating system analogous to those found on mobile phones allowing users to perform a single task at a time. The processing technology does vary among players, so whether these machines can be called computers is debatable, however if devices such as the I-POD or the SONY net Walkman can be proven to be Turing-complete as described within digital practice, then these machines can be considered to be computers.
References
www.webopaedia.com - accessed 28th January 2005
www.wikipedia.org - accessed 28th January 2005
Bibliography
Brookshear, J. G. (2000). Computer Science, An Overview. Addison-Wesley