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Steve Jobs and Steve Wozniak started the personal computer craze with their Apple brand computer. IBM rushed a personal computer to the market, with has the side-effect of making Microsoft the behomoth that it is. Apple and IBM started the home computer craze, but only Apple used their own operating system. IBM had to use a 3rd party operating system. Eventually, IBM computers used MS-DOS. This is the second article in the series on how computers work. The other articles are:

• Part 1: The CPU
• Part 2: The Boot Process
• Part 3: Early Apple Computers and MS-DOS (this blog entry)
• Part 4: Windows 1 to Windows 3.11
• Part 5: Windows 95 Based Operating Systems
• Part 6: Windows NT Based Operating Systems
• Part 7: Windows Vista Based Operating Systems
• Part 8: Unix and Linux Operating Systems
• Part 9: MacIntosh

The Apple II series

The Apple II was the first fully-assembled personal computer. A person had to build the Apple I. Unlike modern computers, Apple II really had no true operating system built-in. That is because it didn't have a hard drive, only 5 1/4" floppy disks. To run a program, you inserted the disk of the program and booted from the disk. However, due to technical limitations, on the original Apple II a user had to press a few buttons to start the process. The program loaded an operating system and then immediately executed the program. This would be different than a PC where you would insert a disk to load the operating system and then use the command line to execute the program. The Apple II was popular in schools just for this very reason. Eventually hard drives became a real possibility in personal computers and Apple did move the operating system to the hard drive. The Apple IIGS, the last Apple II computer, had a graphical user interface (GUI) that was like the now released Mac GUI.

What made the Apple II so successful was Steve Wozniak's engineering prowass. Wozniak was able to figure out many hardware shortcuts. These shortcuts required some clever programming, but the benefit was costs were greatly reduced. In fact, the first Apple II used several software tricks to keep hardware requirements to a minimum. Each Apple II in the series was fully compatible with older software.

The Apple II underwent many changes over its life. Eventually, Apple replaced the whole name with the Macintosh name.

What kept the Apple from becoming the dominant player in the computer world was the lack of clones. To maintain quality, Apple controlled everything and still does today. Making a computer that was Apple compatible was difficult because everything was in its infancy. Now, Apple takes active steps to prevent others from making Apple clones but hasn't stopped people from successfully doing it.

The operating systems used on the Apple II were called AppleDOS, ProDOS, and GS/OS.

AppleDOS was first. Starting with the popular Apple II+, a user would put the disk in and the operating system would boot and load itself into memory. Then the OS would then load a startup program as specified by the disk. AppleDOS did not support hard drives and the newer 3 1/2" floppy disks. Next came ProDOS. It had support for newer hardware but it didn't last long because it was replaced by GS/OS. GS/OS was the first GUI operating system for the Apple II series. GS/OS was really a way to transition from Apple II to Mac.

Macintosh

Many people will remember the iconic Mac Super Bowl commercial called 1984. The idea behind the commercial was the competiton was like evil Big Brother from George Orwell's book Nineteen Eighty-Four. This theme Apple would play to for years. We are cool and chic, they (at this time IBM but eventually Microsoft) are conformists.

The Mac did change the computer world. It made the graphical user interface, or GUI, affordable to the masses. Graphical user interfaces were far superior than the old command line interfaces (CLI) and booting straight to the program found on all older computers. The GUI provided ease of use with flexibility. Eventually, all computers would be GUI. Although the Mac operating system was revolutionary, it was very much incomplete when it first came out. That was to be expected, of course, because something this complex was fairly new and thus had to work out many issues. Apple did not invent the GUI, Xerox corporation did. But Xerox did help Apple develop their GUI.

The Mac introduced many concepts. It would be years before Microsoft had a true answer. Microsoft Windows 1 and Windows 2 were very much inferior to Mac OS. In fact, Windows 1 to Windows 3 were just complex MS-DOS programs. The Mac popularized icons to represent programs, the menu bar, and drag-and-drop. Although the Mac OS could only run one program at a time, it did enable a user to switch between programs at will. The background program was suspended. The Mac OS also made it easier to communicate between computers.

The Macs sold well, for a time, thanks to the effective Apple advetising. But Apple would never gain market dominance even with the Mac because of the lack of clones. This concept will be discussed below. Overall, not much is known how the early Apple computers work.

MS-DOS

When Apple came out with their computer, the computer world changed. IBM had been a leading technology company and suddenly they were behind in a big way. Because IBM was desperate, they could not dictate the deals like Apple could. Such a move ended up benefiting Microsoft and Intel in a big way.

IBM had to get something to market quickly. Of the two choices IBM had in front of them for a CPU, they chose the Intel 8088, a cheaper version of the Intel 8086. The reason for choosing this CPU was because supplies were plentiful thus IBM could produce computers faster. Such rapid decisions had some good consequences as well. IBM was forced to use industry standard designs to avoid long engineering design delays.

So now IBM had the hardware, they now needed the software. IBM approached Microsoft. Microsoft made an add-on for the Apple II that allowed the Apple II to run an early version of what became MS-DOS called CP/M. But Microsoft did not an operating system. So Microsoft told IBM to go Digital Research, which made the CP/M operating system. But Digital Research did not want to meet IBM's request. So IBM went back to Microsoft. This time, Microsoft did not turn down IBM. But Microsoft still needed an operating system. So Bill Gates bought an operating system for a bargain, renamed it MS-DOS, and the rest is history. The theme of coping others' ideas is one Microsoft still uses.

It didn't take long for companies to reverse engineer the IBM machine. Soon clones were cropping up and Microsoft had the good sense not to limit themselves just to IBM. That is why Microsoft operating systems are the most widely used in the world.

The BIOS, discussed in an earlier blog entry, is responsible to getting the operating system started. The first thing MS-DOS does is load the IO.SYS file. This file loads essential hardware drivers for the next step, which is loading the MSDOS.SYS file. MSDOS.SYS is the actual MS-DOS operating system. These two files are required.

After MSDOS.SYS is loaded, it looks for the optional CONFIG.SYS file. This file, although optional, contains some very important features. It loaded features that allowed MS-DOS to use more than 640KB of memory, a limitation of the Intel 8086 and 8088 CPU's. It allowed MS-DOS to use a mouse or CD drive. And other important DOS initialization features.

When CONFIG.SYS is finished, MSDOS.SYS then loads COMMAND.COM. At this point, MS-DOS is ready to go. However, if the AUTOEXEC.BAT file exists, COMMAND.COM executes the instructions contained therein. Quite often, certain device drivers required entries in both CONFIG.SYS and AUTOEXEC.BAT. AUTOEXEC.BAT would also set certain parameters needed for programs to operate. Once AUTOEXEC.BAT finished, the user had the familar command prompt.

MS-DOS allowed files with certain extensions to run. The most common was files ending in .EXE. This is the most common type of executable file. The next file was one ending in .COM. This is not to be confused the .com internet addresses. In MS-DOS, .COM files were like .EXE files but with support for less of the MS-DOS features. In short, they are more primative files. The final type of file that MS-DOS could execute is the .BAT file, a batch file. These are text files that contain a list of commands to be executed. In later versions of MS-DOS, these could become quite complex allowing the user to create text menus.

MS-DOS also had some built-in commands. These include CHDIR or CD for changing subdirectories, CLS for clear screen, COPY for copying files, DEL or ERASE for deleting files, DIR to list the files in the current working directory, ECHO to have MS-DOS print the words that followed (used for batch files), MD or MKDIR to create a subdirectory, RD or RMDIR to remove a empty subdirectory, REN to rename a file, and other less common commands.

When MS-DOS first came out, it could only do one task as a time. Once the operating system loaded, it waited for the user or a batch file to give it commands. To execute a file, it is sufficient to just type the file name with the .BAT, .COM, or .EXE part.

The fact is, MS-DOS is very simple and basic. It became popular only because Microsoft had good marketing sense and because of several coincidences. There were many variants of DOS, IBM just chose Microsoft. And because IBM had to rush something to market, they were forced to use something they could not fully control which allowed others to make identical computers. This had the benefit of making IBM compatible computers, as they were called, more affordable. Which had market benefits to Microsoft because MS-DOS had to be used to be IBM compatible. The process was started, Microsoft was destined to be a behomoth because IBM compatible computers were cheaper and thus more common than Apple computers.

Apple continued to innovate, while Microsoft was slow to change to maintain backwards compatibility. Maintain compatibility with older programs is actually very important because businesses are even slower to change due to the high cost of re-learning a new system. Being slow helped Microsoft become entrenched in businesses despite the lack of innovation. Intel, which made the CPU's, also worked hard to main backwards compatibility, but the problems with this were always pushed to programmers. Microsoft had to do something to match Apple's GUI. That something was Windows 1 and Windows 2. Both of these were essentially fancy DOS programs. It wouldn't be until the Windows 3 variants in 1990 that Microsoft really had a solid GUI. And it wouldn't be until Windows NT released in 1993 that Microsoft would have a true GUI operating system. Windows to Windows 3.11 will be discussed in the next article.