Many discoveries and inventions have directly and
indirectly contributed to the development of the personal
computer. Examining a few important developmental landmarks
can help bring the entire picture into focus.
Personal Computing History
A modern digital computer is largely a collection of
electronic switches. These switches are used to represent, as
well as to control, the routing of data elements called
binary digits (or bits). Because of the
on or off nature of the binary information and signal routing
used by the computer, an efficient electronic switch was
required. The first electronic computers used vacuum tubes as
switches, and although the tubes worked, they had many
problems.
The tube was inefficient as a switch. It consumed a great
deal of electrical power and gave off enormous heat--a
significant problem in the earlier systems. Primarily because
of the heat they generated, tubes were notoriously
unreliable--one failed every couple hours or so in the larger
systems.
The invention of the transistor, or semiconductor, was one
of the most important developments leading to the personal
computer revolution. The transistor was invented in 1948 by
Bell Laboratories engineers John Bardeen, Walter Brattain, and
William Shockley. The transistor, which essentially functions
as a solid-state electronic switch, replaced the much less
suitable vacuum tube. Because the transistor was so much
smaller and consumed significantly less power, a computer
system built with transistors was much smaller, faster, and
more efficient than a computer system built with vacuum
tubes.
The conversion to transistors began the trend toward
miniaturization that continues to this day. Today's small
laptop (or palmtop) PC systems, which run on batteries, have
more computing power than many earlier systems that filled
rooms and consumed huge amounts of electrical power.
In 1959, engineers at Texas Instruments invented the
integrated circuit (IC), a semiconductor circuit that
contains more than one transistor on the same base (or
substrate material) and connects the transistors without
wires. The first IC contained only six transistors. By
comparison, the Intel Pentium Pro microprocessor used in many
of today's high-end systems has more than 5.5 million
transistors, and the integral cache built into some of these
chips contains as many as an additional 32 million
transistors! Today, many ICs have transistor counts in the
multimillion range.
In 1969, Intel introduced a 1K-bit memory chip, which was
much larger than anything else available at the time. (1K bits
equals 1,024 bits, and a byte equals 8 bits. This chip,
therefore, stored only 128 bytes--not much by today's
standards.) Because of Intel's success in chip manufacturing
and design, Busicomp, a Japanese calculator manufac-turing
company, asked Intel to produce 12 different logic chips for
one of its calculator designs. Rather than produce 12 separate
chips, Intel engineers included all the functions of the chips
in a single chip.
In addition to incorporating all the functions and
capabilities of the 12-chip design into one multipurpose chip,
the engineers designed the chip to be controlled by a program
that could alter the function of the chip. The chip then was
generic in nature, meaning that it could function in designs
other than calculators. Previous designs were hard-wired for
one purpose, with built-in instructions; this chip would read
from memory a variable set of instructions that would control
the function of the chip. The idea was to design almost an
entire computing device on a single chip that could perform
different functions, depending on what instructions it was
given.
The first microprocessor--the Intel 4004, a 4-bit
processor--was introduced in 1971. The chip operated on 4 bits
of data at a time. The successor to the 4004 chip was the 8008
8-bit microprocessor, introduced in 1972.
In 1973, some of the first microcomputer kits based on the
8008 chip were developed. These kits were little more than
demonstration tools and did little except blink lights. In
late 1973, Intel introduced the 8080 microprocessor, which was
10 times faster than the earlier 8008 chip and addressed 64K
of memory. This breakthrough was the one that the personal
computer industry had been waiting for.
MITS introduced the Altair kit in a cover story in the
January 1975 issue of Popular Electronics magazine. The
Altair kit, considered to be the first personal computer,
included an 8080 processor, a power supply, a front panel with
a large number of lights, and 256 bytes (not kilobytes) of
memory. The kit sold for $395 and had to be assembled. The
computer included an open architecture bus (slots) that
prompted various add-ons and peripherals from aftermarket
companies. The new processor inspired other companies to write
programs, including the CP/M (Control Program for
Microprocessors) operating system and the first version of the
Microsoft BASIC (Beginners All-purpose Symbolic Instruction
Code) programming language.
IBM introduced what can be called its first personal
computer in 1975. The Model 5100 had 16K of memory, a
built-in 16-line-by-64-character display, a built-in BASIC
language interpreter, and a built-in DC-300 cartridge tape
drive for storage. The system's $9,000 price placed it out of
the mainstream personal computer marketplace, which was
dominated by experimenters (affectionately referred to as
hackers) who built low-cost kits ($500 or so) as a
hobby. The IBM system obviously was not in competition for
this low-cost market and did not sell well.
The Model 5100 was succeeded by the 5110 and 5120 before
IBM introduced what we know as the IBM Personal Computer
(Model 5150). Although the 5100 series preceded the IBM PC,
the older systems and the 5150 IBM PC had nothing in common.
The PC IBM turned out was more closely related to the IBM
System/23 DataMaster, an office computer system introduced in
1980. In fact, many of the engineers who developed the PC at
IBM had originally worked on the DataMaster.
In 1976, a new company called Apple Computer introduced the
Apple I, which sold for $695. This system consisted of a main
circuit board screwed to a piece of plywood; a case and power
supply were not included. Only a few of these computers were
made, and they reportedly have sold to collectors for more
than $20,000. The Apple II, introduced in 1977, helped set the
standard for nearly all the important microcomputers to
follow, including the IBM PC.
The microcomputer world was dominated in 1980 by two types
of computer systems. One type, the Apple II, claimed a large
following of loyal users and a gigantic software base that was
growing at a fantastic rate. The other type, CP/M systems,
consisted not of a single system but of all the many systems
that evolved from the original MITS Altair. These systems were
compatible with one another and were distinguished by their
use of the CP/M operating system and expansion slots, which
followed the S-100 (for slots with 100 pins) standard. All
these systems were built by a variety of companies and sold
under various names. For the most part, however, these
companies used the same software and plug-in hardware. It is
interesting to note that none of these systems were PC-
compatible, or Mac-compatible, the two primary standards in
place today!
The IBM Personal Computer
At the end of 1980, IBM decided to truly compete in the
rapidly growing low-cost personal computer market. The company
established what then was called the Entry Systems Division,
located in Boca Raton, Florida, to develop the new system.
This small group consisted of 12 engineers and designers under
the direction of Don Estridge; the team's chief designer was
Lewis Eggebrecht. The division developed IBM's first real PC.
(IBM considered the 5100 system, developed in 1975, to be an
intelligent programmable terminal rather than a genuine
computer, even though it truly was a computer.) Nearly all
these engineers had been moved to the new division from the
System/23 DataMaster project, which in 1980 introduced a small
office computer system that was the closest predecessor to the
IBM PC.
Much of the PC's design was influenced by the DataMaster's
design. In the DataMaster's single-piece design, the display
and keyboard were integrated into the unit. Because these
features were limiting, they became external units on the PC,
although the PC keyboard layout and electrical designs were
copied from the DataMaster.
Several other parts of the IBM PC system also were copied
from the DataMaster, including the expansion bus (or
input/output slots), which included not only the same physical
62-pin connector but also almost identical pin specifications.
This copying was possible because the PC used the same
interrupt controller as the DataMaster and a similar direct
memory access (DMA) controller. Expansion cards already
designed for the DataMaster could then be easily re-designed
to function in the PC.
The DataMaster used an Intel 8085 CPU, which had a 64K
address limit, as well as an 8-bit internal and external data
bus. This arrangement prompted the PC design team to use the
Intel 8088 CPU, which offered a much larger (1M) memory
address limit, and an internal 16-bit data bus, but only an
8-bit external data bus. The 8-bit external data bus and
similar instruction set allowed the 8088 to be easily
interfaced into the earlier DataMaster designs.
Estridge and the design team rapidly developed the design
and specifications for the new system. In addition to
borrowing from the System/23 DataMaster, the team studied the
marketplace, which also had enormous influence on the IBM PC's
design. The designers looked at the prevailing standards,
learned from the success of those systems, and incorporated
into the new PC all the features of the popular systems--and
more. With the parameters for design made obvious by the
market, IBM produced a system that filled its niche in the
market perfectly.
IBM brought its system from idea to delivery in one year by
using existing designs and purchasing as many components as
possible from outside vendors. The Entry Systems Division was
granted autonomy from IBM's other divisions and could tap
resources outside the company, rather than go through the
bureaucratic procedures that required exclusive use of IBM
resources. IBM contracted out the PC's languages and operating
system to a small company named Microsoft. That decision would
be the major factor in establishing Microsoft as the dominant
force in PC software today.
NOTE: It is interesting to note that IBM had
originally contacted Digital Research (the company that
created CP/M, then the most popular Personal Computer
operating system) to have them develop an operating system
for the new IBM PC, but they were leery of working with IBM,
and especially balked at the non-disclosure agreement IBM
wanted them to sign. Microsoft jumped on the opportunity
left open by Digital Research, and as a result has become
one of the largest software companies in the world. IBM's
use of outside vendors in developing the PC was an open
invitation for the aftermarket to jump in and support the
system--and it did.
On Wednesday, August 12, 1981, a new standard was
established in the micro- computer industry with the debut of
the IBM PC. Since then, hundreds of millions of PC-compatible
systems have been sold as the original PC has grown into an
enormous family of computers and peripherals. More software
has been written for this computer family than for any other
system on the market.
The IBM-Compatible Marketplace 16
Years Later
In the more than 16 years since the original IBM PC was
introduced, many changes have occurred. The IBM-compatible
computer, for example, advanced from a 4.77MHz 8088-based
system to 300MHz or faster Pentium II-based systems--nearly
2,000 times faster than the original IBM PC (in actual
processing speed, not just clock speed). The original PC had
only one or two single-sided floppy drives that stored 160K
each using DOS 1.0, whereas modern systems easily can have 10G
(10 billion bytes) or more of hard disk storage. A rule of
thumb in the computer industry is that available processor
performance and disk-storage capacity at least double every
two to three years. Since the beginning of the PC industry,
this pattern has shown no sign of changing.
In addition to performance and storage capacity, another
major change since the original IBM PC was introduced is that
IBM is not the only manufacturer of "PC-compatible" systems.
IBM originated the PC-compatible standard, of course, and it
continues to set standards that compatible systems follow, but
the company does not dominate the PC market as it did
originally. More often than not, new standards in the PC
industry are developed by companies and organizations other
than IBM. Today it is Intel and Microsoft who are primarily
responsible for developing and extending the PC hardware and
software standards, respectively. Some have even taken to
calling PCs "Wintel" systems, owing to the dominance of those
two companies.
Even so, there are literally hundreds of system
manufacturers producing computers that are fully PC
compatible, not to mention the thousands of peripheral
manufacturers whose components expand and enhance
PC-compatible systems.
PC-compatible systems have thrived, not only because
compatible hardware can be assembled easily, but also because
the primary operating system was available not from IBM but
from a third party (Microsoft). The core of the system
software is the BIOS (Basic Input Output System), and this was
also available from third-party companies like AMI, Award,
Phoenix, and others. This situation allowed other
manufacturers to license the operating system and BIOS
software and to sell their own compatible systems. The fact
that DOS borrowed the functionality and user interface from
both CP/M and UNIX probably had a lot to do with the amount of
software that became available. Later, with the success of
Windows, there would be even more reasons for software
developers to write programs for PC-compatible systems.
One of the reasons why Apple Macintosh systems will likely
never enjoy the success of PC-compatibles is that Apple
controls all the software (BIOS and OS), and until recently
had not licensed any of it to other companies for use in
compatible systems. Apple now seems to recognize this flawed
stance because they have begun to license this software;
however, it seems too late for them to effectively compete
with the PC-compatible juggernaut. It is fortunate for the
computing public as a whole that IBM created a more open and
extendible standard. The competition among manufacturers and
vendors of PC-compatible systems is the reason why such
systems offer so much performance and so many capabilities for
the money.
The IBM-compatible market continues to thrive and prosper.
New technology continues to be integrated into these systems,
enabling them to grow with the times. Because of the high
value that these types of systems can offer for the money and
the large amount of software that is available to run on them,
PC-compatible systems likely will dominate the personal
computer marketplace for perhaps the next 15 to 20 years as
well.
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