How a computer really works

Generally a computer is a tool to simplify different tasks and reduce the amount of time needed for them. As you all hopefully know, there is the hardware, which is the part of a computer that physically exists e.g. you can touch it. On the other hand software is simply said a set of instructions that allows a computer to carry out several tasks.

The Central Processing Unit is the most important part of every computer today in use. A modern processor (like lntel's Pentiurn Pro) has about 5.5 million transistors. Each of those transistors functions basically as a switch, e.g. it can either be turned on or off and thus each represents a binary digit, O or I. Although more calculations have to performed than for example in our normal ten based system, it can be much better adapted to electronic devices.

The calculations in the C PU are performed through logical connections with the transistors. The lntel Pentium Pro, which is the fasted processor currently available on the market for a normal horne computer, cando up to two MIPS.

A processor stores the instant values of calculations in his registers, but larger values have to be stored in memory, which is much slower.

The C PU communicates with all other devices, like hard disk, graphic card or memory through a communication device called the bus. A; slow bus would be the bottleneck of a computer, because nearlyall the data goesthrough the bus.

Memory is also made out of transistors. While somebody works at his computer, the programs, their values, which have not yet been saved to hard disk, and the operating system are in memory .Memory is not a permanent storage, because if you turn off your computer, the whole content is naturally lost, because all transistors lose their current state.

The hard disk is a device for storing programs and data. It's not like the processor or the memory made out of transistors, it's a plate rotating at high speed, on which the data is represented magnetically.

The motherboard hosts the processor, the memory, the bus and interface cards (like graphic card, sound card, etc. )

Without software a computer is just a dump machine.

On the motherboard you find a small chip in which the BIOS is stored. The BIOS provides basic functions for screen output, 1/0 operations and for the keyboard. If there were no BIOS, your computer would not react, if you were to press a key on the keyboard.

Software can generally be categorized in:

Without an operating systems a llnormal" person could not do anything with a computer, because it would be too complicated.

It extends the functionality of the B10S and provides advanced functions for screen output (color!), 1/0 operations, etc. It might also provide a GU1, where you can use your mouse. Today's comrnon operating systems for personal computers are: DOS, Microsoft Windows or . IBM's OS/2. While DOS has no GU1, Windows and OS/2 both have one. Thus it's much easier to use Windows or OS/2 because you just use your mouse to click, etc.

Modem Qperating systems like Windows or OS/2 provide hundreds of AP1-functions which a programmer can use in his application. For example, Windows has an AP1-function called IIpSet". With it you can simply draw a point on the screen, through specifying where you want it to be printed and what color it shotild have. This is however a very simple function, but it already requires many calculations to be performed by the processor .

Normally an operating system is composed of the kemel, which is the essential core of the operating system, drivers and utilities and maybe of a GUI.

Applications are the software, you actually work with. Common applications are ward pracessars, spreadsheets or graphic programs. So applications allow you to write text or make graphics, etc. They are partially based on API-functions, which are provided by the operating system. Like operating systems applications have to be programmed. There are different programming languages, for example BASIC, C, or Assembler, but each language has its advantages and disadvantages. Printing something on the screen for example in BASIC is much easier than doing this in Assembler. The cores of operating systems are most I y developed in C and Assembler, applications for example in Pascal, C or Visual Basic. Assembler programs are very fast, but it's very difficult to program them and it's takes a lot of time. On the other hand programming Visual Basicapplications is quite easy and fast, but the program itself it executed rather slowly.

1. Processor jumps to first illStructioll ill ROM BIOS. 2

2. ROM BIOSperforrns various Power-Oll SeIf-Test (e.g. processor check, etc.) 3. lllitialization of graphic card

4. Memory, disk and floppy drive check

5. Master Boot Record is loaded and given control

I Startvorgang eines Computers

2 standard for lntel and compatible processors

9. Load system registry (information about programs, hardware, etc. )

Second Reality is a demo programmed by the Future Crew in 1992. A demo is a program normally made by fanatic teenagers to show w hat you do with a normal horne computer. The Future Crew is a so-called "programming-crew" and with Second Reality they woll the Assembly '93 competition. The whole demo is programmed in pure Assembler (about 10000 code lines, however not including sound, graphics and rendering). The development took the Future Crew, whichhas ten members aged between 18 to 20, eight months. The high speed of this demo is only achieved through special mathematical techniques. Everything in this demo except the'rendering has to be calculated by the processor in real-time.

Computer terms:

MIPS -millioninstructions per second (measure for the~speed ofa processor) memory -Arbeitspeicher, Hauptspeicher (ROM) BIOS -basic input output system

I/O (input/output) -E/A (Eingabe/Ausgabe) interface card -Schnittstellenkarte DOS -Disk Operating System

OS/2 -Operating System /2 (operating system from IBM)

GUI (graphical user interface) -graphische Benutzeroberfläche

API (application programming interface) -set offunctions, which can be used in .ipplicaiions word processor -Textverarbeitung spreadsheet -Tabellenkalkulation

driver (Treiber) -software which translates instructions given by the computer so that a specific hardware device can understand them

utility (Hilfsprogramm) -for ex~ple disk management programs

BASIC (Beginners All Purpose Symbolic Instruction Code) -easy programming language Assembly -annual competition in Finland for demos

real-time (Echtzeit) -duringthe execution ofthe program