Falk Joensson's
Learning Programming with Eas
(Easy Application Script Tutorial)

How the Computer Works:09. Levelling Up

The computer is an ongoing collaborative project of generations of scientists, engineers and software developers, each generation building on the achievements of the past. These principles are true for many other technological implementations, but none other than the computer sees them so condensed and in such a rapid succession. The computer thus truly is mankind's highest cultural, scientific and technological achievement. (Unfortunately its users, especially generation web 2.0, are at large far behind it and use it accordingly.) This chapter will, as an example for the continuous improvement, explain the development of programming languages. The program memory of very early computers was only a ROM (read-only memory), in the form of punched cardboard cards and later punched paper tape. The holes in the card or tape allowed electrode balls or pins to contact the other electrode (wheel or strip) under the card/tape, thus setting a bit in the control unit. The program pointer was increased by a mechanical drive moving the card or strip by one row forward. Programming was done by punching the holes painstakingly in the card or tape, using reference tables to look up which desired effect needed which type of bit pattern. These programs were thus written directly in machine code, the bare bits, which meant a lot of work to achieve, compared with modern programs, only very rudimentary tasks. But some people got very good at this, and passionate enough, to write ever longer, ever more complex programs this way. They got a computer to accept keystrokes from a simple keyboard, to save the entered text on an automatically punched tape, to read this text again from the tape in order to append to it in a later session ... ... and finally to walk through some text, perform various pretty elaborate calculations and generate from the text new machine code — at which point the first programming language was born, assembler, making programming in machine code obsolete overnight. Programming in assembler meant writing source code as actual text commands, on a computer keyboard. Then this text gets read by the assembler compiler program which creates from it the machine code to punch into the tape. Still today, every computer and every microcontroller has its own assembler (but not writing to tape anymore), upon which everything else rests. Because the machine code is different for every microcontroller and microprocessor, so differ the assemblers. Assembler thus is a concept, not a single language. Assembler uses shorthand commands that stand for one or for several machine-code commands. Reference tables tell the programmer how many processor cycles each assembler command really takes. To give you an impression, here are four typical assembler commands:
MOV A,B
= "move from A to B" Copies the register result byte read from the address A to the address B. (Some assemblers use MOV B,A instead.)
ADD 7
Adds the constant 7 to the last result of the ALU.
NOP
= "no operation" The NOP command is used to let the computer wait a tick, for instance to synchronize with slower I/O data protocols.
JNZ l1
= "jump (on) non-zero" If the last result of the ALU was not zero, the program pointer is set to the address calculated by the compilter from the label "l1". Labels are set as source code text lines and can be used conveniently instead of fixed address constants. The "l1" above could be set for instance via the line (between command lines):
l1:
Also, assemblers introduced variables, names for memory addresses that will be assigned by the compiler. And again, some people got so good at this, and passionate enough, to develop with assembler the next step, actual programming languages. These parse more or less readable source code lines of variable lengths that are shorthands often for dozens of assembler lines, or for entire assembler sub-programs. Also, they make many abstractions that are, compared with assembler, much closer to what we as humans are used to think in, for example from language grammar (like if-then-else and loop types) or mathematical formulas. Also, proper programming languages can be used on various microprocessor types. Each type needs its own compiler for the programming language, so a line like "a = b + c*d" may be performed differently on different microprocessors (machine code), but the line itself is always the same in the given programming language and always has the same defined effect. Many programming languages have been developed, all with their own features, ideas, strengths — and weaknesses. Only a few reached widespread use, and their success was not always proportional to their overall quality, rather a result of corporate marketing. Therefore, by far the most influential programming language became one simply named "C", a comparatively cryptic language that is as un-clever as its name and is full of traps that let programmers easily make catastrophic errors. All early programming languages were still quite cumbersome to use, but some people again used them to implement new, better programming languages that added ever more comfortable features and avoided the traps and errors of the old ones. Or so it should have been. In reality, the next generation often were just reformed versions of the old languages, so from C came C++ and C# for example, but they kept most of the drawbacks of the old languages. Also, new languages added ever more sophisticated features that came from academic theorists and were heavily marketed, but only slow programs down, make them use up more and more RAM and disk space and don't really improve productivity. But marketing is strong, as it abuses psychology as a professional, all-year active big industry, so you will find many people who, despite scientifically proven otherwise, will claim that for instance object-oriented programming is a really great thing. As the internet became seriously important, special programming languages got developed, for instance PHP for programming software that runs on a web server and manages safe logins, storing user data, and so on, and JavaScript for programming software that runs in web browsers and lets the displayed web page react dynamically to user input, or is used to animate elements on the page. Pretty much all of these are based on C, but did some really heavy reforms that make using them much more comfortable — but the programs run slower than C programs. This is because in C, the programmer needs to define how many bytes a variable shall have (fixed variable types) and constantly needs to pay attention to this setting throughout the code — in PHP, JavaScript etc however, variables can change their type anytime and the program does all the checks and conversions on the fly, every single time a variable is used or set. And again, even newer programming languages get created, such as Eas which in the current Eas 4B implementation compiles to JavaScript, therefore is yet a bit slower than JavaScript, but as a really totally new-designed language from the ground up, it has none of the usual traps and drawbacks that all C descendents have, and it is most comfortable to use. The story will continue, and I think that the biggest potential lies in finally shaking off the ballast of the old languages by fully replacing them through modern-language machine-code compilers. Why? Because my experience with big software projects is that the greatest advancements invariably are only made by starting all over again from scratch, after having learned from working with the old code for some generations/versions. For instance, in one company they had a crucial microcontroller program that had been improved continuously by various programmers in succession. When it was handed to me, I threw it away and rather wrote it all from scratch — after just two weeks, my program was 1,000 times faster, had more features and was (in contrast to the old program) absolutely reliable.
09. Levelling Up
T Two Things You Need
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