FREE ESSAY ON THE FIRST CHAPTER OF COMPUTER LANGUAGES

THE FIRST CHAPTER OF COMPUTER LANGUAGES

The Tortuous Path of Early Programming.
In the perpetual darkness more than two miles below the surface of the North Atlantic, a
submersible sled slowly traced the alpine contours of the ocean bottom in the summer of
1985. Named the Argo after the ship in which the legendary Greek Hero Jason sought the
Golden Fleece, the 16-foot-long craft resembled a section of scaffolding flung on its
side and stuffed with equipment, Powerful lights, sonar, Video cameras. Far above,
arrayed in front of a video screen in the control room of the U.S. Navy research vessel
Knorr, Members of a joint French-American scientific expedition intently watched the
images transmitted by the submersible as it was towed above a desolate landscape of
canyons and mud slides.
After 16 days of patient search, A scattering of metallic debris appeared on the screen,
followed by the unmistakable outline of a ship's boiler. A jubilant cry arose from the
scientists. The ocean liner Titanic sunk 73 years earlier with more than 1,500 of its
2,200 passengers on board had finally been found.
The quest for the remains of the Titanic in the crushing depths of the sea was a
remarkable application of computer technology, as exotic in its means as in its venue.
Not least of the keys to the successful outcome was the agility of modern computer
programming.
Argos's ensemble of sonar, lights and cameras was orchestrated by an array of computers
that each programmed in a different computer language. The computer on the unmanned Argo
itself was programmed in FORTH, a concise but versatile language originally designed to
regulate movement of telescopes and also used to control devices and processes ranging
from heart monitors to special-effects video cameras. The computer on the Knorr was
programmed in C, a powerful but rather cryptic language capable of precisely specifying
computer operations. The telemetry System at either end of the finger thick Co-ax cable
connecting the vessels, which in effect enabled their computers to talk to each other,
was programmed in a third, rudimentary tongue known as assembly language.
Programming languages are the carefully and Ingeniously conceived sequences of words,
letters, numerals and abbreviated mnemonics used by people to communicate with their
computers. Without them, computers and their allied equipment would be useless hardware.
Its own grammar and syntax regulate each language. A programming language that
approximates human language and can generate more than one instruction with a single
statement is deemed to be high-level. But computer languages tend to be much more sober
and precise than human languages. They do not indulge in multiple meanings, inflections
or twists of iron. Like computers themselves, computer languages have no sense of
humour.
Today there are several hundred such languages, considerably more than a thousand if
their variations, called Dialects, are counted. They enable their users to achieve a
multitude of purposes, from solving complex mathematical problems and manipulating (or
crunching) business statistics to creating musical scores and computer graphics. No
existing Language is perfect for every situation. One or more of three factors usually
determines the choice among them: The language is convenient to the programmer; it is
useable on the available computer; it is well suited to the problem at hand. The multiple
tongues employed on the Titanic expedition are a case in point. For the computers aboard
the surface ship Knorr, C was the preferred language because it provided more direct
control of the computerised hardware. FORTH was the only high-level language that could
be used on the submersible Argo's computer. And the precise timing required timing
required of the signals passed by cable between the two vessels was best accomplished by
rigid assembly language.
As varied languages have become the all build on a common base. At their most fundamental
level, Computers respond to only a single language, The high and low of electric voltages
representing the ones and zeros of binary code. Depending on how these signals are fed
into a computer's memory. Another might be a piece of data yet to be processed.
Yet another collection of binary digits, or bits, might command the machine to perform a
certain action, such as adding to numbers. The circuitry of each type of computer is
designed to respond to a specific and finite set of these binary encoded machines, which
may be combined and recombined to enable the machine to perform a vast range of tasks.
Though straightforward enough this so-called machine is a forbidding, alien language to
human beings. A computer program of any size, in its machine-code form, consists of
thousands or even millions of ones and zeros, strung together like beads on a seemingly
interminable string. A mistake in even one of these digits can make the difference
between a program's success and failure.
Less than half a century ago, machine code was the only means of communicating with
computers. Since then, generations of language designers have harnessed the power of the
computer to make it serve as its own translator. Now, when a programmer uses the command
PRINT Hello or the statement LET A = B * (C - D) in a program, a translating program is
called into action, converting those commands into the ones and zeros that the machine
can understand. 
Paper Tape and Plug-Boards
The methods used to program the world's first general-purpose computers were as
cumbersome and primitive as the machines they served. The historic Mark 1, assembled at
Harvard University during World War 2, was a five-ton conglomeration of relays, shafts,
gears and dials, 51 feet long. It received its instructions for solving problems from the
spools of punched paper tape that were prepared and fed into a computer by small corps if
technicians. A more advanced machine, ENIAC (for Electronic Numerical Integrator and
Computer), was completed in 1945 at the University of Pennsylvania's Moore School of
Electrical Engineering. Unlike the Mark 1, which was electromechanical, ENIAC was fully
electronic. But it was still devilishly difficult to program. Its primary developers,
Physicist John W. Mauchly and engineer J. Presper Eckert, had responded to the urgencies
of wartime by concentrating on ENIAC's hardware. Programming took a back seat. ENIAC was
not even equipped to receive instructions on paper tape. To prepare it for operation, ma
team of technicians had to set thousands of switches by hand and insert hundreds of
cables into plug boards until the front of the computer resembled a bowl of spaghetti.
Not surprisingly, ENIAC's users tried to squeeze the last drop of information out of any
given configuration before they undertook to change it.
These early experiences made it all too plain that a better means of communicating with
the machine with the machine was needed if computers were to approach their potential.
And even as ENIAC hummed through its first electronic calculations, some forward-looking
work on a higher level programming was being done elsewhere. In at least one case,
however, many years would pass before the results came to light. 
The Plan Calculus
Konrad Zuse's world was crashing down around him early in 1945 as the allied military
noose tightened on Berlin, his home city. The young German engineer had been working
since before the war on a series of relatively small, general-purpose computers, using
the living room of his parents apartment as his laboratory. Zuse's efforts were a notable
example of parallel yet independent developments in science; he had no idea of the
similar progress being made in other nations, and his own government had shown little
interest in his computer work. Shortly before the fall of Berlin, Zuse loaded his only
surviving computer, dubbed the Z4, onto a wagon and fled with a convoy of other refugees
to a small town in the Bavarian Alps.
During the grim years immediately after the war, Zuse found himself without either funds
or facilities to work on computer hardware. Turning his energies to theory instead, he
sought a better way to program a computer, not specifically the Z4, but any similar
machine. What was needed, he decided, was a system of symbolic and numeric notations
based on a logical sequence, in affect a calculus of problem-solving steps.
Working alone, Zuse devised a programming system that he named Plan Calculus, or, in
Germen, Plankakul. He wrote a manuscript explaining his creation and applying it to a
variety of problems, including sorting numbers and doing arithmetic by means of binary
notation (other computers of the day operated in decimal). He also taught himself to play
chess and then produced 49 pages of program fragments in Plankakul that would allow a
computer to assess a player's position. It was interesting for me to test the efficiency
and general scope of the Plankakul, Zuse later wrote, by applying it to chess problems.
Zuse never expected to see his language actually run on a computer. The Plankakul he
wrote, arose purely as a piece of desk work, without regard to whether or not machines
suitable for Plankakul programs would be available in the foreseeable future. Although he
briefly visited the United States in the late 1940s, only small portions of his
manuscript were published, much less implemented, in the decade after the war; many of
his ideas for a systematic, logical language remained unknown to an entire generation of
computer linguists. Not until 1972 did Zuses's experts to wonder what effect Plankakul
would have had if it had been disseminated earlier. it shows us how different things
might have been, one critic of subsequent languages has noted, how what we have today is
not necessarily the best of all possible worlds.
While Zuse was labouring in isolation, a collegial effort to develop a programming
language for real machine was under way at academic centres in Great Britain and the
United States, where the earliest computers were beginning to be used. But progress was
slow. Not only did each computer have its own machine code and programming method, but
also developing the machines themselves required the lion's share of the scientists' time
and talent.
During the years immediately after the war, most programmers continued to work on machine
code, the binary digits that correspond to a computer' circuits. To make the job slightly
easier, some of them began using shorthand number systems to denote combinations of bits,
a method akin to a stenographer's using symbols to represent words when taking dictation.
The first of these systems was Base eight, also known as octal. Just as there are only
two digits, 0 and 1, in the binary system, there are eight in octal, the numerals 0
through to 7. Each of these octal numbers is used to represent one of eight possible
combinations of three bits (000, 001, 010, 011, 100, 101, 110 and 111). A more ambitious
numbering system that followed is base 16, or Hexadecimal (hex, to us programmers),
Gathered into groups of four. The 16 possible combinations of four bits were represented
by the numerals 0 through to 9 and the letters A through to F. Eg. Black #000000 White
#ffffff.
A Penchant for Gadgets
To at least one frustrated American programmer, the modest progress offered by such
number systems seemed grossly insufficient. Grace Murray Hopper was accustomed to being
in the vanguard. She had grown up fascinated by things mechanical, gadgets, she called
them. As a girl of seven she had taken apart all the wind-up alarm clocks in her family's
summer home in New Hampshire, to discover how they worked, However she could not put them
back together. The 'spanking' that followed failed to dim her scientific enthusiasm.
After graduating with honours from Vassar College in 1928, she earned a Ph.D in
mathematics at Yale, a rare achievement for a female, and then returned to Vassar to
teach.
At the height of World War 2, Hopper joined the U.S. Naval Reserve, and in June 1944 she
earned her commission. Her contribution through the years would be prodigious. Lieutenant
Hopper was assigned to the navy team that was developing programs for the Mark 1 at
Harvard. Mark 1 was the biggest, prettiest gadget I'd ever seen, She later Said.
The programming team Hopper joined consisted of two male ensigns, she subsequently
learned that when the men heard that a grey-haired old college professor was coming, one
of them bribed the other so that he would not have to take the desk next to hers. Hopper
soon proved her worth as a programmer, however. I had an edge, she said. I had studied
engineering as well as mathematics, and I knew how the machine worked from the beginning.
Of course, I was lucky. When I graduated in 1928, I didn't know there was going to be a
computer in 1944.
In 1949, a civilian again, Hopper joined the fledgling Eckert-Mauchly Computer
Corporation, Which was operating out of a old factory in North Philidelphia. Mauchly and
Eckert had left the University of Pennsylvania's Moore School in 1946 after a bitter
fight over patent right to their electronic computers. Once ain business for themselves,
they secured several contracts and set about building a new machine that they hoped would
prove the commercial viability of computing. They called the machine the Universal
Automatic Computer, or UNIVAC.
The Hidden Perils of Octal
Grace Hopper had learned how to work in octal, teaching herself to add, Subtract,
multiply and even divide in the strange system. The entire establishment was firmly
convinced that the only way to write and efficient program was in octal, she later
lamented (the prevailing view was that the computers time was more valuable than the
programmer's; if a program could be executed swiftly, the difficulty of writing it was
immaterial). And indeed octal proved very helpful in getting the company's prototype
computer up and running. She was having trouble balancing her personal bank account, an
embarrassing dilemma for a trained mathematician. Finally, she appealed to her brother,
who was a banker, and after several evenings' work he solved the mystery. Occasionally
she was subtracting a check in octal rather than the decimal system in the bank, and
everyone else used. I face a problem of living in two different worlds, Hopper said. That
may have been one of the things that motivated me to get rid of octal as much as
possible.
Hopper's efforts to ease the programmer's burden (and keep her chequebook balanced) would
eventually shape the course of computing. But she was not alone in the attempt. Shortly
before she came to Philadelphia, John Mauchly made a suggestion that would take
programming a first tentative step beyond octal and Hexadecimal's. He directed his
programmers to devise a computer language that would allow a person to enter problems
into the machine in algebraic terms, an approach that Konrad Zuse would have approved of.
By the end of 1949, the system, known as Short Code, was operational. Later promoted as
an electronic dictionary, it was a primitive high-level language and a definite
improvement over machine code. A programmer first wrote the program to be solved in the
form of mathematical equations and then used a printed table to translate their equation
symbols into two-character codes. For instance, a parenthesis became 09, while the plus
symbol became 07. A separate program in the computer then converted these codes to ones
and zeros, and the machine performed the appropriate functions.
Short Code's partner program was essentially a primitive interpreter, a language
translator that converts the high-level statements in which a program is written into
simpler instructions for immediate execution. As programming languages evolved,
interpreters would become one of the two basic categories of language translators.
New advances in languages soon overtook Short Code, but its central idea endured. Far
from being simply glorified adding machines, computers are consummate manipulators of
symbols, whether those symbols represent numbers, letters, colours, or even musical
notes. A computer has no difficulty taking the code numerals 07 and performing the
sequence of steps that leads it to add two numbers, as long as it has been programmed to
recognise 07 as the symbol for addition. In the same manner, it can take a complete
statement, such as IF N * 100 THEN PRINT N/47, and translate it into the basic machine
instructions that will enable the hardware to carry out the desired task. This purposeful
manipulation of symbols is the fundamental principle behind all programming languages.
Although short code was never a commercial success, the language made a deep impression
on Grace Hopper. Short code was the first step toward something which gave a programmer
the power to write a program in a language that bore no resemblance whatsoever to the
original machine code, she said. But before the promise of Short code could be realised,
much more had to be done.
The British Contribution
The pace of progress in computer languages was tightly bound to advances in computer
hardware, and during the late 1940s there were few such advances. Most of them were
influenced by Mauchly and Eckert's early work and could in fact trace their origins to a
specific event: a series of lectures held at the Moore School in the summer of
1946.There, Mauchly and Eckert discussed the successor to ENIAC they were planning.
Dubbed the Electronic Discrete Variable Automatic Computer, or EDVAC, it would
dramatically reduce the labour involved in changing from one program to another by
storing its programs and date electronically in an expanded internal memory.
One participant in that summer was Maurice V. Wilkes, then head of the Mathematical
Laboratory at Cambridge University. Inspired by the lectures, Wilkes returned to England
and set about designing a machine based on the EDVAC concept, construction began in 1947.
Named the electronic storage Automatic Calculator, or EDSAC, it became operational in
1949, well before Mauchly and Eckert's firm produced its first commercial computer.
Like many early computers, EDSAC was a finicky performer. One programmer recalled that
even the sound of a airplane flying overhead could bring it to a halt. Whatever EDSAC was
shut down for any reason, a set of initial orders had to be loaded into the machine to
enable it to accept programs again. This process made a whiring sound, which was a signal
for everyone who wanted to use the computer to come running, Programs in hand. Those
fortunate enough to have offices nearest the computerusually ended up in the front of the
queue. The others might have to wait a long time. 
At first, EDSAC could perform 18 basic operations (modern computers usually have a
capability of 200), each of them triggered by a particualar sequence of ones and zeros.
Early on, EDSAC's designers decided not to force its programmers to use this machine code
in their programs. instead they set up a system of mnemonics in which each machine
instruction was represented by a single capital letter. Thus S meant Subtract, I meant
Read the next row of holes T meant Transfer information to storage and Z meant Stop the
machine. When a programmer typed a mnemonic on a specially adapted keyboard, the
corresponding binary instruction was punched into a papertape, which could then be fes to
the machine.
Buiding a Library.
Even more valuable than the mnemonics devised for EDSAC was the library of subroutines
set up for the machine. Subroutines were already a familiar concept in computing: Grace
Hopper and her group had used the on the Harvard Mark 1. But they continued to pose their
own peculiar problems. Subroutines are independant sections of the computer program that
are used over and over and are called for by the main program when needed.Early
programmers often kept notebooks containing the comman used subroutines so that they did
not have to start from scratch when one was needed. The problem was that the addresses
that designated where each of a subroutine's instructions and varibles were to reside in
memory changed according to where the subroutine occured in the program.
Maurice Wilked called the EDSAC scheme of mnemonics and subroutines an assembly system,
Commanly known as Assembly.
Assembly code reamsins in use today because of its close relation to the machine, an
assembly language is machine-specific, designed to correspond to the set of machine-code
instructions wired into a particular computer's CPU. Thus, assembly lanuage is a
favourite of programmers who want to compress their programs into the smallest possible
space in memory and have them run as fast and efficiently as possible. These attributes
made it ideal for programming the telemetry system used by the Titanics finders.
Anyone writing in assembly language has to be intimately familiar with how a computer
does things, To know, for example, the many steps required simply to add 2 numbers.
Assembly written for one computer would be totally gibberish to another computer.The
language was a creation of a brilliant english mathematician Alan M. Turing. 
By 1948, Turing was in charge of programming he prototype of a real computer called Mark
1, the machine that was being constructed at the University of Manchester. (It was not
related to the Mark 1 of Harvard). The manchester Mark 1used combinations of five binary
digits to represent the machines different instructions, with each instruction requiring
four such combinations, or 20 bits. Intending to make the Mark 1 easier to program ,
Turing installed a system in which a mnemonic symbol was substituted for each of the 32
combinations of Zeros and Ones possible with a five-bit code. The symbols Turing assigned
to the combinations were the letters, numerals and punctuation mark of a standard
teleprinter keyboard. For Example, a slash (/), or stroke to the British, stood for
00000, or zero, an R stood for 01010, and so up to a ?, representing 11111.
That is the end of part one of the four part series. Please download or read the
following files in the near future. I hope that you find this file helpfull. 
Bibliography
Time - Warner Books,