The last three digits specified the operation addition, subtraction, and so on , while the first thirteen signified the address either of another instruction or of a piece of data.
The binary system is ideal for machines but awkward for people. The system was really a mnemonic code — and a clumsy one at that — whose symbols, entered via a teleprinter, were automatically translated into binary math by the computer. There was nothing complicated about the translation process; every letter and symbol was turned into a predetermined binary number, and then executed.
Williams, who headed the Mark I project and who invented electrostatic storage tubes, wrote a little gambling program that counted the number of times a given digit, from 0 to 9, was produced by a run of the generator. But Williams adjusted the generator to lean toward his favorite number, and he enjoyed betting against unsuspecting visitors.
The beginnings of computer crime! This instruction set was called Short Code, and it enabled algebraic equations to be written in terms that bore a one-to-one correspondence to the original equations.
That is, it did not produce cards or tape that had to be reentered into the machine; it carried out the program automatically.
Although Remington Rand made many extravagant claims for Short Code, you still had to supply detailed instructions for every operation. In the early s, most computers were used for scientific and engineering calculations. These calculations involved very large numbers, and the usual way of writing a number — groups of figures separated by a comma — was inconvenient. Instead, programmers used the floating-point system of numerical notation, which reduced big numbers to a more manageable size.
A floating-point number is a fraction multiplied by a power of two, ten, or any figure. For example, 2, is. All this was essentially before programmers had the luxury of inputting data through a keyboard and view it on a screen. It's hard to be certain about the very first assembler hard to even define what that was.
Years ago, when I wrote a few assemblers for machines that lacked assemblers, I still wrote the code in assembly language. Then, after I had a section of code reasonably complete I translated it into machine code by hand. Those were still two entirely separate phases though -- when I was writing the code, I wasn't working or thinking at a machine-code level at all. I should add that in a few cases, I went a step further: I wrote most of the code in an assembly language I found simpler to use, then wrote a tiny kernel more or less what we'd now call a virtual machine to interpret that on the target processor.
That was deathly slow especially on a 1 MHz, 8-bit processor , but that didn't matter much, since it normally only ran once or at most, a few times.
You don't need an assembler to hand assemble assembly language code into machine code. Just as you don't need an editor to write assembly language code.
The first assemblers were probably written in assembly language and then hand assembled into machine code. Even if the processor had no official 'assembly language' then programmers probably did most of the job of programming using some kind of pseudo code before translating that code into machine instructions.
Even in the earliest days of computing , programmers wrote programs in a kind of symbolic notation and translated them into machine code before feeding it into their computer. In Augusta Ada King's case, she would have needed to translate them into punched cards for Babbage 's Analytical Engine , but alas it was never built. The back of the manual had all of the information you needed to translate Z80 assembly language into machine code even inclusing all of the weird index mode opcodes the Z80 had.
I would write out a program on paper in assembly language and dry-run through the code. When I was happy that my program was bug-free, I would look up each instruction in the back of the manual, translate it into machine code and write the machine code down on the paper too.
Finally I would type all of the machine code instructions into my ZX81 before saving it to tape and trying to run it. If it didn't work, I would double check my hand assembly and if any translation was wrong I would patch the bytes loaded from tape before re-saving it and trying again to run the program. From experience, I can tell you that it is much easier to debug your code if it is written in assembly language than in machine code - hence the popularity of disassemblers.
Even if you don't have an assembler, hand assembling is less error prone than trying to write machine code directly, though I guess a Real Programmer like Mel might disagree. There is no difference then or now. You want to invent a new programming language, you choose one of the languages available to you today to make the first compiler.
If all you had was pencil and paper and some switches or punch cards as your user interface to the first or next new instruction set, you used one or all of the items available to you. You could very well have written an assembly language, on paper, and then used an assembler, you, to convert it into machine code, maybe in octal, then at some point that went into the interface to the machine.
The first computing machines were not general purpose machines that you could use to create assemblers and compilers from. You programmed them by moving some wires between the output of the prior alu to the input of the next. Eventually you had a general purpose processor such that you could write an assembler in assembly, hand assemble it, feed it in as machine code, then use that to parse ebcdic, ascii, etc.
Think of punch cards and paper tape. Instead of flipping switches you could most definitely make a completely mechanical machine, a labor saving device, that created the media the computer would read. Instead of having to enter the machine code bits with switches like an altair you could instead feed paper tape or punch cards using something mechanical, not processor driven, that fed the memory or processor, OR using a small machine code written boot loader.
This was not a bad idea because you could make something, driven by the computer that could also mechanically produce the paper tapes or punch cards, and then feed those back in. Two sources of punch cards, the non-computer based mechanical labor saving device, and the computer driven machine. There are one or two instances in Brook's computer zoo where he said something like "the mnemonics are our invention, the designer simply used numeric opcode or the character whose code was the opcode", so there where machines for which there wasn't even an assembly language.
Entering programs end debugging at the front panel for those who haven't done it, it was a way to set up the memory, you set some switches to the address, some others to the value and pressed a button, or another button to read the value was common far later.
Some old timers brag they would still be able to enter the boot code for machines they used extensively. The difficulty of writing directly machine code and reading programs from memory dump is quite dependent on the machine language, some of them are relatively easy the hardest part is tracking the addresses , x86 is one of the worse.
I built a computer in It was very advanced over its contemporary the Altair, because it had a 'monitor rom' which let me enter programs by typing in machine code in hex and viewing this code on a video monitor, where as with the Altair each machine instruction had to be entered a bit at time using a row of switches.
So yes, in the early days of computers and then again in the early days of personal computers people did write applications in machine code.
When I learned assembly language, on the Apple ][, There was a program included in the ROM called the micro-assembler. It did immediate translation of assembly instruction to bytes, as you entered them. This means there were no labels -- if you want to jump or load, you had to calculate the offsets yourself. It was much easier than looking up the instruction layouts and entering hex values though. No doubt, real assemblers were first written using the micro-assembler, or some other not quite complete environment.
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Assembly Language. Share 1. I agree to Cleverism's.
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