VB haters, look away
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Arrays start at 1 - just like when counting your fingers. C# (C, C++...) messed up, who counts anything from zero? It's unnatural, zero simply does not exist.
Sin tack the any key okay
Lopatir wrote:
who counts anything from zero?
Everybody, but many don't realize it. Zero is a perfectly good value for counting. For instance, there are zero elephants in this room. Whenever you count something you always start with zero, then you count the first item as one. It's just so intuitive, you don't really think about it.
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CodeWraith wrote:
You dimension an array to n elements
No, you dimension it for n+1, as per the spec.
DIM X(5)
n=5, so our array now should have six elements, indexed 0 - 5. Strange way of sying that you want six eggs, but ok. At least we use the same value to dimension the array and the highest valid index. In the end it is a just a question of specifications and conventions. However, the original problem was at the beginning of the array. Of course we could access the array with 1 - 6, but that would be even more confusing. So, where do you think the habit to dimension the arrays one element too large, accessing them with 1 to n and wasting element 0 came into play?
I need a perfect, to the point answer as I am not aware of this. Please don't reply explaining what method overloading is
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Member 7989122 wrote:
It goes: 4, 3, 2, 1, -1
It says "-1"? That would confuse a lot of people.
It does. This is not a new independent building, but a new wing. The elevators in the old wings go 4, 3, 2, 1, U - the U is for "underetasje", or "sub-floor". (For buildings having two basement levels, it is common to label them U1 and U2.) I guess that the reason why they changed it is that we have a large fraction of foreign employees who don't speak Norwegian, so the management (or elevator constructor?) wanted something language independent. You could say that "U" indicateds "underground", but even an English based abbreviation is sort of language dependent :-). Sure, almost everybody around has at least some understanding of English, but sometimes very little and limited to professional job terms; in the elevator their mind is never tuned in to English. A U is about as good as a Chinese ideograph - just some blurb that makes little sense except symbolizing the basement level.
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To be fair if you type "bytecode" into google most of the links returned refer to java rather than the more generic usage. The former would suggest a definition of 'type of' where the latter would not require the comparison.
If Google had existed in the early 1980s, a search for "bytecode" would have returned thousands of references to Pascal and its P4 bytecode format. The Pascal compiler was distributed as open source, with a backend for a virtual machine (also available as open source for a couple architectures). You could either adapt the VM to the architecture of your machine, and keep the compiler unchanged, or you could replace the P4 code generating parts of the compiler with binary code generation for your own machine. Actually, lots of interpreters for non-compiled languages of today do some compilation into some sort of bytecode, which is cached up internally so that e.g. a loop body needs to be symbolically analyzed only on the first iteration. But Java is the only language (after Pascal and its P4) to really focus on this, making "Java Virtual Machine" a marketing concept, and really pushing "compile once, run anywhere" as The Selling Point of the language (more so 20 year ago than today). So you are right: Java is very prominent in bytecode references.
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All correct, but are you disagreeing with 'C# is compiled to a type of bytecode'?
My immediate reaction: Yes, I would disagree. Bytecodes are ready for execution, while the dotNET output from a C# compiler is not. You could say that I am using a "narrow" defintion of the term, but the term could have a more general meaning. Yes, it could - it could mean any code representation that is built up of bytes. Like source code :-). We could even generalize the "byte" concept: The old Univac mainframes could work with 9 bit bytes (4 to the word) or 6 bit bytes (6 to the word), while DEC-10 and DEC-20 had 7-bit bytes (5 to the word and one spare bit). But that is not the commmon "compiler guy" interpretation of "bytecode". The linearized DAG is not directly executable, like a bytecode. Obviously, you could, at run time, do a just-in-time compilation into a bytecode for an interpreter, rather than compiling into native binary code. But at least as far as I know, there are no virtual machines directly interpreting dotNET assemblies with no pre-execution processing step. In my student days, we were a group of students making an attempt to build a direct interpreter for the intermedidate language from another front end compiler (for the CHILL programming language), having a similar architecture. We soon realized that the data structures required to maintain the current exeuction state would be immensly large and complex; the task of building the interpreter would far exceed making a complete backend compiler. You couldn't do without a unified symbol table. You couldn't do without a label-to-location mapping. You couldn't do without a lot of state information for various objects. You couldn't do without ... So we never completed the project. (It was a hobby project, not a course assignment.)
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My immediate reaction: Yes, I would disagree. Bytecodes are ready for execution, while the dotNET output from a C# compiler is not. You could say that I am using a "narrow" defintion of the term, but the term could have a more general meaning. Yes, it could - it could mean any code representation that is built up of bytes. Like source code :-). We could even generalize the "byte" concept: The old Univac mainframes could work with 9 bit bytes (4 to the word) or 6 bit bytes (6 to the word), while DEC-10 and DEC-20 had 7-bit bytes (5 to the word and one spare bit). But that is not the commmon "compiler guy" interpretation of "bytecode". The linearized DAG is not directly executable, like a bytecode. Obviously, you could, at run time, do a just-in-time compilation into a bytecode for an interpreter, rather than compiling into native binary code. But at least as far as I know, there are no virtual machines directly interpreting dotNET assemblies with no pre-execution processing step. In my student days, we were a group of students making an attempt to build a direct interpreter for the intermedidate language from another front end compiler (for the CHILL programming language), having a similar architecture. We soon realized that the data structures required to maintain the current exeuction state would be immensly large and complex; the task of building the interpreter would far exceed making a complete backend compiler. You couldn't do without a unified symbol table. You couldn't do without a label-to-location mapping. You couldn't do without a lot of state information for various objects. You couldn't do without ... So we never completed the project. (It was a hobby project, not a course assignment.)
Nah, op-codes are ready for execution, bytecodes are not. I like this definition: Bytecode is a form of hardware-independent machine language that is executed by an interpreter. It can also be compiled into machine code for the target platform for better performance.
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Nah, op-codes are ready for execution, bytecodes are not. I like this definition: Bytecode is a form of hardware-independent machine language that is executed by an interpreter. It can also be compiled into machine code for the target platform for better performance.
If you are right, then terminology is changing. In my book, the op-code is that field in the binary instruction code that indicates what is to be done: Add, shift, jump, ... Usually, the rest of the binary instruction code is operand specifications, such as memory addresses or constants. In more high-level contexts I have seen "op-code" used for a field in a structure, e.g. a protocol. Again, the opcode tells what is to be done (at the level of "withdraw from bank account", "turn on" etc.), the other fields tells with what is it to be done. You suggest a new interpretation, that an op-code is both the 'what to do' and the 'with what to do it'. Maybe that is an upcoming understanding, but certainly not the traditional one. JVM bytecodes are certainly ready for execution, once you find a machine for it. It is easier to build a virtual machine, a simulator, than to build a silicon one. So that is what we do. You can build a translator from MC68000 instructions to 386 instructions. Or from IBM 360 instructions to AMD64 instructions. Or from JVM instructions to VAX instructions. Suggesting that the intention of compiling to MC68K instructions was to serve as an intermediate step to 386 code would be crazy - that was never the intention of the MC68K instruction set. Similarly, the intention of Java bytecodes were not to be translated into another instruction set. If you first compile to one instruction set (including bytecode, such as Java or Pascal P4 bytecode), and then translate to another instruction set, there is generally a loss of information, so that the final code is of poorer quality than if it had been compiled directly from the DAG, which usually contains a lot of info that is lost (i.e. used and then discarded) in the backend. Some of it may be recovered by extensive code analysis, but expect to loose a significant part, in the sense that you will not utilize the target CPU fully. Especially if the first/bytecode architecture has a different register philosophy (general? special?), interrupt system or I/O mechanisms. So, if at all possible, generate the target code from the intermedate level, not from some fully compiled instruction set.
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One of the "beauties" of the stock C# switch statement was that using integer case qualifiers it compiled to a mean and lean jump-table in CIL. I assume it still does; have yet to see any performance comparisons of use of the new features and other techniques for switch-a-roo. I like the new features.
«Differences between Big-Endians, who broke eggs at the larger end, and Little-Endians gave rise to six rebellions: one Emperor lost his life, another his crown. The Lilliputian religion says an egg should be broken on the convenient end, which is now interpreted by the Lilliputians as the smaller end. Big-Endians gained favor in Blefuscu.» J. Swift, 'Gulliver's Travels,' 1726CE
Note that this is not at all set by the language defintion, but 100% decided by the compiler writer. I have seen compilers (not C#) that generate completely different code depending on the optimization switches: If you optimize for speed, and the case alternatives are sparse, you may end up with a huge jump table. If you optimize for code size and the number of specific cases is small, it might compile like an if ... elseif ... elseif ... When you switch on strings, hash methods are sometimes used to reduce the number of string comparisons that must be done. Compilers may try out several different methods of compiling a switch statements, and assign scores to each alternative based on the compiler options, such as optimization and target architecture. The one with the highest score wins, and is passed on to later compiler stages. This sure slows down compilation, but is generally worth it. A small sidetrack, but closely related: Contrary to common belief, modern standards for sound and image processing, such as MP3 and JPEG, does not specify how the compression is to be done, only how a compressed file is decompressed. A good compressor may try out a handful of different ways to compress the original (sometimes varying wildly in compressed encoding), decompress according to the standard and do a diff with the source material. The alternative with the smallest diff result is selected. (Or, the size of the diff result gives that alternative fewer or more points on the scoreboard, together with e.g. compressed size). The compress-decompress-diff-evaluate sure takes CPU power, but today we have plenty of that, at least for sound and still images.
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Brent Jenkins wrote:
It looks like it was more of a legal thing with Sun
One of the points of java was that you were supposed to be able to run it on any VM on any supported OS. Microsoft made specific changes to their java that made it impossible to run on different VMs or even compile. CNN - Sun alleges new Java violations by Microsoft - July 13, 1998[^]
Hey, but we've got .NET Core now :-D :thumbsup:
Now is it bad enough that you let somebody else kick your butts without you trying to do it to each other? Now if we're all talking about the same man, and I think we are... it appears he's got a rather growing collection of our bikes.
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Doesn't C#'s ``foreach`` come from VB's ``For Each``? AFAIK C++ doesn't have any equivalent.
We still miss some loop constructs that are offered by other languages. One that I miss the most is for ListElementPointer in ListHead:NextField .... to traverse a singly linked list, linked through NextField. Then I miss the value set: for CodeValue in 1, 3, 10..20, 32 do ... (a total of 14 iterations). And then, another favorite: for ever do ... In C, I sometimes "simulate" this by #define ever (;;). Finally, I miss the alternative loop exits, where you specify a different loop tail depending on whether the value set was exhausted or the loop was terminated prematurely because some condition was fulfilled: for ... do ... code ... while ... maybe more code ... exitwhile ...code handling premature loop termination... exitfor ...code handling value set exhausted termination... An important aspect of the exitfor/exitwhile is that the code is inside the scope or the for statement, so that e.g. variables decalared within the for is available to the tail processing. If you want to simulate this by setting some termination flag and then break, and after the loop testing: if TerminationCause=exhaustion do else , then what went on in the loop is essentially lost, so this is certainly not a good replacement (and it takes a lot more typing). Finally, for all sorts of nested constructs: I strongly favor that a label identifies a block, rather than a point. I want to be able to do an: exit InnerLoop; or: exit OuterLoop; or even: exit MyProcedure; without the need for setting all sorts of flags that must be tested after InnerLoop and after OuterLoop and from there take new exit to an outer level. You could say that this is little more than syntactic sugar. Sure, but syntactic sugar makes programming sweet.
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CodeWraith wrote:
When they did not want the licenses for J anymore
Errr...after a long trial MS agreed not to do java anymore. If they didn't want it then they wouldn't have fought so long to keep it.
CodeWraith wrote:
that went further from the beginning (no primitive data types, a common CLR across
Can't imagine that that wouldn't be required to avoid more legal trouble. For example look at java on the Android and the Oracle suit about that. The technology itself just encapsulates the business need, but the business need required that it be different.
> If they didn't want it then they wouldn't have fought so long to keep it. Not a reasonable conclusion. On more than one occasion Microsoft has engaged in litigation to slow down the opposition, deplete their resources and demoralise them. Microsoft did this to Sybase while Microsoft Access was being prepared, and was caught very much on the back foot when it unexpectedly _won_ the rights to the source code for SQL Server. PeterW -------------------- If you can spell and use correct grammar for your compiler, what makes you think I will tolerate less?
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[Visual J++ - Wikipedia](https://en.wikipedia.org/wiki/Visual\_J%2B%2B)
Quote:
Microsoft later developed the C# ("C Sharp") language as the primary language for the .NET platform, which was in many ways influenced by Java; subsequently the .NET Framework shares many ideas in common with Java. Much like Java, C# is compiled to a type of bytecode (called CIL), and runs on top of a virtual machine called the Common Language Runtime in .NET. Visual Studio 2005 was the last release to include J#.
Now is it bad enough that you let somebody else kick your butts without you trying to do it to each other? Now if we're all talking about the same man, and I think we are... it appears he's got a rather growing collection of our bikes.
That reference is saying the similarity is with the .NET Framework to the Java platform. Don't confuse the C# Language (or any language) with the .NET Framework which facilitates "managed code" and JIT compilation, similar (and in response) to the 'Java platform' i.e. CIL(MSIL) is synonymous with Java bytecode, CLR synonymous with JRE/JVM etc.
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DIM X(5)
n=5, so our array now should have six elements, indexed 0 - 5. Strange way of sying that you want six eggs, but ok. At least we use the same value to dimension the array and the highest valid index. In the end it is a just a question of specifications and conventions. However, the original problem was at the beginning of the array. Of course we could access the array with 1 - 6, but that would be even more confusing. So, where do you think the habit to dimension the arrays one element too large, accessing them with 1 to n and wasting element 0 came into play?
I need a perfect, to the point answer as I am not aware of this. Please don't reply explaining what method overloading is
Designers were ahead of their time maybe. And early practitioners weren't smart enough to grok the concept. It reminds me of strings in Pascal -- you get a maximum of 255 characters preceded by how many characters are currently in the string. 'Tis possible that BASIC's designers had expected developers to use the zeroth element to hold the count of how many elements are in use.
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One of the "beauties" of the stock C# switch statement was that using integer case qualifiers it compiled to a mean and lean jump-table in CIL. I assume it still does; have yet to see any performance comparisons of use of the new features and other techniques for switch-a-roo. I like the new features.
«Differences between Big-Endians, who broke eggs at the larger end, and Little-Endians gave rise to six rebellions: one Emperor lost his life, another his crown. The Lilliputian religion says an egg should be broken on the convenient end, which is now interpreted by the Lilliputians as the smaller end. Big-Endians gained favor in Blefuscu.» J. Swift, 'Gulliver's Travels,' 1726CE
I think that is the reason that it took so long to upgrade the switch statement. I would expect that you are right an it still with do that. Of course could also do a string which would be a little more complex, and I am sure there is a different implementation for a int and string. swtich statements are a bad smell, so I look to see if there is a better implementation than a swtich. :-)
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Why didn't they make it multivariable as well, like in CHILL? switch (a, b, c) { (1, 'a', 4.3): ...code; (2, 'A', 0.0): ...code; (2, ELSE, pi): ...code; (3, 'C', *): ...code; ELSE: ...code; } * for a value means "don't care". ELSE for a value means "any value not used in any other switch alternative for this variable. Yes, you CAN make it very messy if you exploit the flexibility for all that it is worth. But a diciplined use can be far more readable than a 20-way switch, each alternative with a 7-15 way (varying among the 20) switch, each of those again with a 2-15 way (varying) switch. Then I'd rather prefer the single, clean, 3-dimensional switch.
Did not have exposure to that. Interesting. Not sure how often it would be useful, but if it helps....
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That reference is saying the similarity is with the .NET Framework to the Java platform. Don't confuse the C# Language (or any language) with the .NET Framework which facilitates "managed code" and JIT compilation, similar (and in response) to the 'Java platform' i.e. CIL(MSIL) is synonymous with Java bytecode, CLR synonymous with JRE/JVM etc.
Member 10815573 wrote:
Don't confuse the C# Language (or any language) with the .NET Framework which facilitates "managed code" and JIT compilation, similar (and in response) to the 'Java platform' i.e. CIL(MSIL) is synonymous with Java bytecode, CLR synonymous with JRE/JVM etc.
I wasn't confusing anything. C# and Java were very similar languages at the point when C# was launched and with good reason - Anders Hejlsberg (who is the lead architect on the team developing the C# language) had previously developed Microsoft's J++ language (Microsoft's discontinued implementation of Java). C# really took many of the good bits of Java while the .NET Framework mirrored the Java platform. [C Sharp (programming language) - Wikipedia](https://en.wikipedia.org/wiki/C\_Sharp\_(programming\_language))
Quote:
James Gosling, who created the Java programming language in 1994, and Bill Joy, a co-founder of Sun Microsystems, the originator of Java, called C# an "imitation" of Java; Gosling further said that "[C# is] sort of Java with reliability, productivity and security deleted."[17][18] Klaus Kreft and Angelika Langer (authors of a C++ streams book) stated in a blog post that "Java and C# are almost identical programming languages. Boring repetition that lacks innovation,"[19] "Hardly anybody will claim that Java or C# are revolutionary programming languages that changed the way we write programs," and "C# borrowed a lot from Java - and vice versa. Now that C# supports boxing and unboxing, we'll have a very similar feature in Java."[20] In July 2000, Anders Hejlsberg said that C# is "not a Java clone" and is "much closer to C++" in its design.[21] Since the release of C# 2.0 in November 2005, the C# and Java languages have evolved on increasingly divergent trajectories, becoming somewhat less similar. One of the first major departures came with the addition of generics to both languages, with vastly different implementations. C# makes use of reification to provide "first-class" generic objects that can be used like any other class, with code generation performed at class-load time.[22] Furthermore, C# has added several major features to accommodate functional-style programming, culminating in the LINQ extensions released with C# 3.0 and its supporting framework of lambda expressions, extension methods, and anonymous types.[23] These features enable C# programmers to use functional programming techniques, such as closures,
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Did not have exposure to that. Interesting. Not sure how often it would be useful, but if it helps....
The CHILL language, providing this, was essentially developed to program network switches. If you have been much in contact with communication guys, you have certainly noted that they love designing protocols as state machines: Any entity is at any time in one of a limited number of states. Whatever happens in the interface is modeled as an atomic event; the event ID being one of a limited set of values. The processing of the event depends on the current state and the event ID. Processing is (conceptually) atomic, and changes the entity state into a new value. So a very common usage would be like (in quasi-C syntax, Chill was somewhat different) switch (state, eventID) { (disconnected, setupReq): ... code to handle a call setup request... (transferMode, dataPacket): ... ... more state/event combinations, with their specific handling ... (transferMode, ELSE): ... error hadling, protocol error, not allowed in transferMode state... ELSE: ... general error handling for illegal event in current state, not treated as a specific case... Now, some protocols are so complex that a "pure" state machine would end up with thousands of states. So the protocol spec defines from one up to a small handful of state variables, which may be thought of as sub-states in most cases (not always, but "sort of like"). So you could add one or more of those state variables as the third switch field, if they should lead to distinctly different handling. (For many switch cases, the switch label would be "Don't care" for that state/eventID combination.) So, for protocols defined as state machines, the multidimensional switch statement is a perfect match. I love that kind of protocol specification! It is terse, lucid, unambiguous, and most of all: It pinpoints all protocol error situations and makes it very clear to you where you should define an error handler, and the reasons for raising this error condition.
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If you are right, then terminology is changing. In my book, the op-code is that field in the binary instruction code that indicates what is to be done: Add, shift, jump, ... Usually, the rest of the binary instruction code is operand specifications, such as memory addresses or constants. In more high-level contexts I have seen "op-code" used for a field in a structure, e.g. a protocol. Again, the opcode tells what is to be done (at the level of "withdraw from bank account", "turn on" etc.), the other fields tells with what is it to be done. You suggest a new interpretation, that an op-code is both the 'what to do' and the 'with what to do it'. Maybe that is an upcoming understanding, but certainly not the traditional one. JVM bytecodes are certainly ready for execution, once you find a machine for it. It is easier to build a virtual machine, a simulator, than to build a silicon one. So that is what we do. You can build a translator from MC68000 instructions to 386 instructions. Or from IBM 360 instructions to AMD64 instructions. Or from JVM instructions to VAX instructions. Suggesting that the intention of compiling to MC68K instructions was to serve as an intermediate step to 386 code would be crazy - that was never the intention of the MC68K instruction set. Similarly, the intention of Java bytecodes were not to be translated into another instruction set. If you first compile to one instruction set (including bytecode, such as Java or Pascal P4 bytecode), and then translate to another instruction set, there is generally a loss of information, so that the final code is of poorer quality than if it had been compiled directly from the DAG, which usually contains a lot of info that is lost (i.e. used and then discarded) in the backend. Some of it may be recovered by extensive code analysis, but expect to loose a significant part, in the sense that you will not utilize the target CPU fully. Especially if the first/bytecode architecture has a different register philosophy (general? special?), interrupt system or I/O mechanisms. So, if at all possible, generate the target code from the intermedate level, not from some fully compiled instruction set.
You're agreeing with me: bytecodes are an abstraction, they for the JVM, not the CPU.
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You're agreeing with me: bytecodes are an abstraction, they for the JVM, not the CPU.
The JVM IS a CPU! Just like any microcoded processor is a CPU. There is no principal difference between microcode breaking down the instruction code into activation of the various circuits, or (compiled) C code doing the same thing. Years ago, I was working on a machine which didn't provide BCD instructions in silicon. Cobol users could either buy a floppydisc with the microcode to give the CPU BCD instructions (microcode was kept in RAM), or they could use the software package that emulated BCD (triggered by the 'Illegal Instruction Code' interrupt). How would you describe the BCD instructions? As "abstractions" like the Java bytecodes? Or as integral to the CPU (even though they triggered an Illegal Instruction Code if the microcode was not installed)? Are all microcoded intstructions "abstractions"? If so, then this CPU as well as a lot of others are all abstractions. The Java bytecodes are just like those BCD instructions, except that they cover the complete instruction set. And I am quite sure that it would be possible to write microcode (for this machine with the BCD) to make the bytecodes the "native instruction set" of the machine - it did provide logarithmic/trigonometic functions and malloc/free as instructions, and microcode was developed so that it executed lisp more or less directly (after a tokenization, of course).
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The JVM IS a CPU! Just like any microcoded processor is a CPU. There is no principal difference between microcode breaking down the instruction code into activation of the various circuits, or (compiled) C code doing the same thing. Years ago, I was working on a machine which didn't provide BCD instructions in silicon. Cobol users could either buy a floppydisc with the microcode to give the CPU BCD instructions (microcode was kept in RAM), or they could use the software package that emulated BCD (triggered by the 'Illegal Instruction Code' interrupt). How would you describe the BCD instructions? As "abstractions" like the Java bytecodes? Or as integral to the CPU (even though they triggered an Illegal Instruction Code if the microcode was not installed)? Are all microcoded intstructions "abstractions"? If so, then this CPU as well as a lot of others are all abstractions. The Java bytecodes are just like those BCD instructions, except that they cover the complete instruction set. And I am quite sure that it would be possible to write microcode (for this machine with the BCD) to make the bytecodes the "native instruction set" of the machine - it did provide logarithmic/trigonometic functions and malloc/free as instructions, and microcode was developed so that it executed lisp more or less directly (after a tokenization, of course).
JVM bytecode is abstract - i.e. it's not your CPU's native opcodes. That's it.