Ah thanks fellas. Always learning.

Just to break it down a little more, you want to consider the different levels of computer architecture.

At the lowest form you have digital circuits. Which is basically the hardware passing electrical current through logic gates that then raise or lower the voltage to establish whether it is open or closed. Grouping these together you can build the basic components of a computer system (ALU, CPU, Registers, etc).

But that isn't readable by a human being. Electrical signals mean nothing. We need another layer of abstraction.

So we add in microcode. This is typically stored in ROM on the CPU, and it groups together bit patterns that make up the instructions that command the machine.But this is hard-coded instructions. We need another layer of abstraction.

So we add in machinecode. This defines the instruction set of the machine, and allows our first way of actually programming the machine. It interprets these bit patterns as 1's and 0's and gives us a way to actually call each instruction to operate the CPU. But 1's and 0's are confusing. We need another layer of abstraction.

So we add in assembly language. This allows us to represent those 1's and 0's with symbols and keywords which is then compiled back into machine code by an assembler. We have now entered the realm of low-level languages. But its still constrained by the architecture. We need another layer of abstraction.

So we add in Java. Now we are in the realm of "high-level languages." The language will abstract away all the native code making it even easier to program. Now you don't need to worry about the architecture. The compiler will take the code you write and convert it to a lower language.

So we have gone from electrical signals to using natural language to code your programs. Each layer adding more and more readability.

Now, in transition to these different layers define the data types which defines what they mean. 4 bytes for an integer, 8 bytes a double, etc. What is signed, unsigned, etc.

The programmer doesn't need to worry about those details because they are abstracted away.

And that is a high-level crash course in computer architecture.

That was delightfully brilliant sir, thank you.

it really depends on the architecture of the specific machine and it's operating system, the following is partly right



except that the 'silly' is really a string of true/false with the interpretation left to the particular program you are using
to give you a few more options:

the string 11111111 will for some architectures mean -0, then 11111110 is -1 and 10000000 is -127 and for other architectures the string 11111111 is -1, with 11111110 being -2 and 10000000 = -128 (check up on one's and two's complement - both are different to what you got) and don't forget that there are plenty different architectures based on different "word/byte" lengths/numbers:
8-bit, 9-bit, 16-bit, 32-bit, 36-bit, 48-bit and 64-bit architectures i have used (and there are/were more like 6-bit and 128-bit)

the 'data' might as well refer to a hardware function which can be executed, not just data
also as indicated by "Azrad" it can be a pointer and some architectures use the first bit as indirect indicator, that is the following bits give the adr where you go or pick up data but if the first bit is set the rest is an adr which can again be a pointer etc etc etc
in the end it depends on the machine code what that string of bits means at the bottom level and then you can manipulate it yourself on the program level
the most interesting one i remember is within a 16-bit architecture which used to pack 3 characters into one 16-bit word, effectively using 5 1/3 bits for each character

hope you are now fully confused

@ "Minkomonster"

no general problem with your description but
assemblers do not compile, they assemble/translate either in single or multiple phases
basic assembly instructions are just mnemonic representation of machine code
some assembly languages have/allow for a macro layer to make the coding faster/easier

This post was edited by brmv on Feb 2 2014 01:41am

My bad on the word "compile." Made a mental note not to use it when I was writing the description for fear that someone would call me out on semantics. The word I meant to use was "convert," but it still managed to creep in there. Synonyms are fun.


Yes. I said it uses symbols and keywords. These would be mnemonic representations.


I left out quite a bit of stuff, as I was not intending to teach a course on ISA.