Operating Systems Intro

I've often heard the comment "Computers are smart".
I really think the credit should be placed where it's due:
To the inventors, researchers, developers and programmers that make the thing useful. Actually, the computer isn't that smart at all. The only thing it can do is sense the presence or absence of a small electical impulse. The presence of an electrical charge is interpreted as a '1', and the absence of a charge is interpreted as a '0'. This is what the original programmers had to work with:

10101101011001001001011101
11001010011011010100011101
10010100101001010001101100
11101001010010100101001010

Even a period, a space or a new line was represented with 1s and 0s! Almost impossible to work with, programmers had to come up with some sort of code or language that a human could understand easier. To develop a new programming language, they would also have to write a program, or code, that would automatically interpret the new language back to 1s and 0s that the computer could understand.

Many different languages were developed but the early ones remained quite cryptic. Still, it was easier than writing 1s and 0s. Here's some Assembly Language:

EXTRN CLEAR_SCREEN:PROC, READ_SECTOR:PROC
EXTRN INIT_SEC_DISP:PROC
DISK_PATCH PROC
MOV AX,DGROUP
MOV DS,AX
CALL CLEAR_SCREEN
CALL READ_SECTOR
CALL INIT_SEC_DISP
MOV AH,4Ch
INT 21h
DISK_PATCH ENDP

See how much easier that is to understand?

Of course, not everyone is a programmer, but lots of people have use for a computer. Operating Systems were developed, written in programming code, and then compiled into executable program files that ran on the computer, interpreting the operators typed commands. They were called Disk Operating Systems (DOS) and there were many different flavours, MS DOS, DR DOS, PC DOS, IBM DOS, etc. Microsoft's MS DOS became the most popular and the most common. Not because it was necessarily the best, but through marketing applications, sales numbers, and lots of luck. Although each DOS has its own unique differences, a lot of the typed commands are the same.These are not programming languages, but operating systems.

Your operating system is like a translator between you (the user) and your computer. It translates your commands and tells the computer how to interpret that command. It's made up of tons of different files that are mini-programs, that perform a specific operation when you type their name at the prompt or click on an icon. A command that has its own file is called an External Command. There is a file that is the OS's command interpretor (translates commands so the computer can perform the task). Usually called command.com, many of the basic commands are written right inside this single file. Commands that are part of command.com are called Internal Commands.

Now, application programs, whether they be a game, a spreadsheet application or a word processing program, are written for specific Operating Systems. They use the Operating System's command set to interpret the functions and duties that they want performed. That's why the boxes these programs come in say right on them (in small letters, I know) whether the application is for DOS, Windows, or Macintosh operating systems.

The Operating System allows you to communicate with your disk drives, printer, monitor, etc. It also allows for communication between the computer and application programs. You must have an Operating System of some kind to operate your computer!

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