Computer Basics

Introduction to the PC   

The technical term for a PC is micro data processor. That name is no longer in common use. However, it places the PC in the bottom of the computer hierarchy:

●  Mainframes are the very largest computers - million dollar machines, which can occupy more than one room, An example is IBM model 390. 

●  Minicomputers are large powerful machines. They typically serve a network of simple terminals. IBM's AS/400 is an example of a minicomputer.

●  Workstations are powerful user machines. They have the power to handle complex engineering applications. They use the UNIX or sometimes the NT operating system. Workstations can be equipped with powerful RISC processors like Digital Alpha or MIPS. 

●   PC's are the smallest in this order: Small inexpensive, mass produced computers. They work on DOS, Windows, or similar operating systems. They are used for standard applications.

The PC's success 

The PC came out in 1981. In less than 20 years, it has totally changed our means of communicating. When the PC was introduced by IBM, it was just one of many different micro data processors. However, the PC caught on. In 5-7 years, it conquered the market. From being an IBM compatible PC, it became the standard.

If we look at early PC's, they are characterized by a number of features. Those were instrumental in creating the PC success. 

●   The PC was from the start standardized and had an open architecture.

●   It was well documented and had great possibilities for expansion.

●   It was inexpensive, simple and robust (definitely not advanced).   

The PC started as IBM's baby. It was their design, built over an Intel processor (8088) and fitted to Microsoft's simple operating system MS-DOS. 

Since the design was well documented, other companies entered the market. They could freely copy the central system software (BIOS) and the ISA bus, since they were not patented. Slowly, a myriad of companies developed, manufacturing IBM compatible PC's and components for them. 

The PC construction 

The PC consists of a central unit (referred to as the computer) and various peripherals. The computer is a box, which contains most of the working electronics. It is connected with cables to the peripherals. Here is a list of the PC components.

Components in the central unit - the computer                                                        

The main board:    

CPU, RAM, cache,   ROM chips with BIOS and start-up programs.                          

Chip sets (controllers). Ports, busses and expansion slots.Monitor                      

Drives:    

Hard disk(s), floppy drive(s), CD-ROM, etc.                                                             

                                                                                                                                      

Expansion cards:                                                                                

Graphics card (video adapter), network controller, SCSI controller.                                

Sound card, video and TV card. Internal modem and ISDN card                            

Peripherals                                                                                                                             
External modem  

Printer
Keyboard and mouse                                                                                                          
Scanner  
Tape drives, etc.  

History of the PC

Computers have their roots 300 years back in history. Mathematicians and philosophers like Pascal, Leibnitz, Babbage and Boole made the foundation with their theoretical works. Only in the second half of this century was electronic science sufficiently developed, to make practical use of their theories. The modern PC has roots back to USA in the 1940's. Among the many scientists, I like to remember John von Neumann (1903-57). He was a mathematician, born in Hungary. We can still use his computer design today. He broke computer hardware down in five primary parts:
●  CPU
●   Input
●   Output
●   Working memory
●   Permanent memory   Actually, von Neumann was the first to design a computer with a working memory (what we today call RAM). If we apply his model to current PC's, it will look like this:

                                                                                                                    

About data 

Our PC's are data processors. PC's function is simple: to process data, and the processing is done electronically inside the CPU and between the other components. That sounds simple, but what are data, and how are they processed electronically in a PC? 

Analog data 

The signals, which we send each other to communicate, are data. Our daily data have many forms: sound, letters, numbers, and other characters (handwritten or printed), photos, graphics, film. All these data are in their nature analog, which means that they are varied in their type. In this form, they are unusable in a PC. The PC can only process concise, simple data formats. Such data can be processed very effectively. 

Digital data 

The PC is an electric unit. Therefore, it can only deal with data, which are associated with electricity. That is accomplished using electric switches, which are either off or on. You can compare with regular household switches. If the switch if off, the PC reads numeral 0. If it is on, it is read as numeral one.
The PC is filled with these switches (in the form of transistors). There are literally millions of those in the electronic components. Each represents either a 0 or a 1, so we can process data with millions of 0's and 1's.

Bits

Each 0 or 1 is called a bit. Bit is an abbreviation of the expression BInary digiT. It is called binary, since it is derived from the binary number system:

0 Equals to one bit

1 Equals to one bit

0110 Equals to 4 bit

01101011 Equals to 8 bit

The binary number system 

The binary number system is made up of digits, just like our common decimal system (10 digit system). But, while the decimal system uses digits 0 through 9, the binary system only uses digits 0 and 1. If you are interested in understanding the binary number system, then here is a brief course. Try if you can follow the system. See how numbers are constructed in the binary system, using only 0's and 1's:

Numbers, as known                       Same numbers in binary system
in the decimal-system                        
                                                                           
0                                                                      0
1                                                                      1
2                                                                     10
3                                                                     11
4                                                                    100
5                                                                    101
6                                                                    110
7                                                                    111
8                                                                   1000

Digital data 

We have seen that the PC appears capable of handling data, if it can receive them as 0's and 1's. This data format is called digital. If we can translate our daily data from their analog format to digital format, they will appear as chains of 0's and 1's, then the PC can handle them. So, we must be able to digitize our data. Pour text, sounds, and pictures into a funnel, from where they emerge as 0's and 1's:

Bytes 

The most basic data processing is word processing. Let us use that as an example. When we do word processing, we work at a keyboard similar to a typewriter. There are 101 keys, where we find the entire alphabet A, B, C, etc. We also find the digits from 0 to 9 and all the other characters we need:,.-;():_?!"#*%&etc..
 All these characters must be digitized. They must be expressed in 0's and 1's. Bits are organized in groups of 8. A group of 8 bits is called a byte.

8 bits = 1 byte, that is the system. Then, what can we do with bytes? First, let us see how many different bytes we can construct. A byte is an 8 digit number. We link 0's and 1's in a pattern. How many different ones can we make? Here is one: 01110101, and here is another: 10010101.

We can calculate that you can make 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 different patterns, since each of the 8 bits can have 2 values. 2 8 (two in the power of eight) is 256. Then there are 256 different bytes!●

Now we assign a byte to each letter and other characters. And since we have 256 patterns to choose from, there is plenty of room for all. Here you see some examples of the "translation:"

Character    Bit pattern     Byte number                                    
                                                       
A                  01000001          65                                                    
B                  01000010          66                                                      
C                  01000011          67                                                        
a                   01100001          97                                                      
b                   01100010          98                                                      
o                   01101111         111                                                        
p                   01110000         112                                                        
q                   01110001         113                                                        
r                    01110010        114                                                        
x                   01111000        120                                                        
y                   01111001        121                                                        
z                   01111010        122
‰                10001001        137
   >               00111110        62
©                 10101001         169      
 9                 00111001         57   
2                  00110010         50      
1                  00110001         49      
~                  01111110        126      
  \                 01011100         92      
  ¼               10111100        188    
  $                00100100         36
  .                 00101110         46
 :                  00111010         58

When you write the word "summer", you write 6 letters. If the computer has to process that word, it will be digitized to 6 bytes. In other words, the word summer occupies 6 bytes in the PC RAM, when you type it, and 6 bytes on the hard disk, if you save it.

About text and code 

Now we have seen the PC's user data, which are always digitized. But there are many different kinds of data in the PC. You can differentiate between 2 fundamental types of data:
● Program code, which are data, that allow the PC to function.
● User data, like text, graphics, sound.
The fact is, that the CPU must have instructions to function. An instruction is a string of data, of 0's and 1's. The CPU is designed to recognize these instructions, which arrive together with the user input data to be processed. The program code is thus a collection of instructions, which are executed one by one, when the program runs. Each time you click the mouse, or hit a key on the keyboard, instructions are sent from your software (program) to the CPU, telling it what to do next.

User data are those data, which tells the software how to respond. The letters, illustrations, home pages, etc., which you and I produce, are created with appropriate software.

Files 

Both program code and user data are saved as files on the hard disk. Often, you can recognize the type of file by its suffix. Here are some examples:

Content                      File name
Program code            START.EXE, WIN.COM, HELP.DLL, VMM32.VXD
User data                   LETTER.DOC, HOUSE.BMP. INDEX.HTM

This is written as an introduction to naming files. The file name suffix determines how the PC will handle the file.