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# Assembly
Assembly (also ASM) is, for any given hardware computing platform ([ISA](isa.md), basically a [CPU](cpu.md) architecture), the lowest level [programming language](programming_language.md) that expresses typically a linear, unstructured sequence of CPU instructions -- it maps (mostly) 1:1 to [machine code](machine_code.md) (the actual [binary](binary.md) CPU instructions) and basically only differs from the actual machine code by utilizing a more human readable form (it gives human friendly nicknames, or mnemonics, to different combinations of 1s and 0s). Assembly is converted by [assembler](assembler.md) into the the machine code. Assembly is similar to [bytecode](bytecode.md), but bytecode is meant to be [interpreted](interpreter.md) or used as an intermediate representation in [compilers](compiler.md) while assembly represents actual native code run by hardware. In ancient times when there were no higher level languages (like [C](c.md) or [Fortran](fortran.md)) assembly was used to write computer programs -- nowadays most programmers no longer write in assembly (majority of zoomer "[coders](coding.md)" probably never even touch anything close to it) because it's hard (takes a long time) and not [portable](portability.md), however programs written in assemCbly are known to be extremely fast as the programmer has absolute control over every single instruction.
Assembly (also ASM) is, for any given hardware computing platform ([ISA](isa.md), basically a [CPU](cpu.md) architecture), the lowest level [programming language](programming_language.md) that expresses typically a linear, unstructured sequence of CPU instructions -- it maps (mostly) 1:1 to [machine code](machine_code.md) (the actual [binary](binary.md) CPU instructions) and basically only differs from the actual machine code by utilizing a more human readable form (it gives human friendly nicknames, or mnemonics, to different combinations of 1s and 0s). Assembly is converted by [assembler](assembler.md) into the the machine code. Assembly is similar to [bytecode](bytecode.md), but bytecode is meant to be [interpreted](interpreter.md) or used as an intermediate representation in [compilers](compiler.md) while assembly represents actual native code run by hardware. In ancient times when there were no higher level languages (like [C](c.md) or [Fortran](fortran.md)) assembly was used to write computer programs -- nowadays most programmers no longer write in assembly (majority of zoomer "[coders](coding.md)" probably never even touch anything close to it) because it's hard (takes a long time) and not [portable](portability.md), however programs written in assembly are known to be extremely fast as the programmer has absolute control over every single instruction (of course that is not to say you can't fuck up and write a slow program in assembly).
**Assembly is NOT a single language**, it differs for every architecture, i.e. every model of CPU has potentially different architecture, understands a different machine code and hence has a different assembly (though there are some standardized families of assembly like x86 that work on wide range of CPUs); therefore **assembly is not [portable](portability.md)** (i.e. the program won't generally work on a different type of CPU or under a different [OS](os.md))! And even the same kind of assembly language may have several different [syntax](syntax.md) formats which may differ in comment style, order of writing arguments and even instruction abbreviations (e.g. x86 can be written in [Intel](intel.md) and [AT&T](at_and_t.md) syntax). For the reason of non-portability (and also for the fact that "assembly is hard") you shouldn't write your programs directly in assembly but rather in a bit higher level language such as [C](c.md) (which can be compiled to any CPU's assembly). However you should know at least the very basics of programming in assembly as a good programmer will come in contact with it sometimes, for example during hardcore [optimization](optimization.md) (many languages offer an option to embed inline assembly in specific places), debugging, reverse engineering, when writing a C compiler for a completely new platform or even when designing one's own new platform. **You should write at least one program in assembly** -- it gives you a great insight into how a computer actually works and you'll get a better idea of how your high level programs translate to machine code (which may help you write better [optimized](optimization.md) code) and WHY your high level language looks the way it does.