"In computer science, a low-level programming language is a programming language that provides little or no abstraction from a computer's instruction set architecture commands in the language map closely to processor instructions. Generally this refers to either machine code or assembly language".
Low level languages must be written for a specific processor architecture and cannot be written or taught in isolation without referencing the processor for which it was written. Unlike higher level languages, using an educational assembly language needs a representation of a processor. Assembly is the most helpful programming language to use for learning about fundamental computer processor operation.
Little Man Computer (LMC) is an instructional model of a simple von Neumann architecture computer with all basic features of modern computers. It can be programmed in machine code (usually decimal). It is based on the concept of having a little man locked in a small room. At one end of the room are 100 mailboxes or (memory), each capable of holding a three digit instruction or data. At the other end of the room are two mailboxes labeled INBOX and OUTBOX which receive and emit data. In the middle of the room is a work area with a simple two function (add and subtract) calculator called the Accumulator and a resettable counter called the Program Counter. The Program Counter is similar to what a doorperson uses to keep track of how many people have entered a facility it can count up 1, or it can be reset to 0. As specified by the von Neumann architecture, memory contains both instructions and data. The user loads data into the mailboxes and then signals the little man to begin execution.
Next Byte Codes (NBC) is a simple language with assembly language syntax that is used to program Lego Mindstorms NXT programmable bricks. The command line compiler emits NXT compatible machine code, and supports Windows, Mac OS X and Linux.
Little Computer 3 (LC-3), is an assembly language with a simplified instruction set, but can be used to write moderately complex assembly programs and is a theoretically viable target for C compilers. It is simpler than x86 assembly but has many features similar to those in more complex languages. These features make it useful for teaching basic programming and computer architecture to beginning college computer science and computer engineering students, which is its most common use.
DLX is a reduced instruction set computer (RISC) processor architecture by the main designers of the MIPS and the Berkeley RISC designs, two benchmark examples of RISC design. DLX is essentially a cleaned up, simplified MIPS, with a simple 32-bit load/store architecture. It is widely used in college-level computer architecture courses.
MIX and MMIX are hypothetical computers used in Donald Knuth's monograph, The Art of Computer Programming (TAOCP). Paraphrasing Knuth: The MIX systems are computers intended to illustrate machine-level aspects of programming, so its machine language is simple, elegant, easy to learn. It also includes all the complexities needed for high performance in practice, so in principle it can be built and perhaps be competitive with some of the fast general-purpose computers. MIX is hybrid programmable in binary and decimal numbers; most programs written for it will work using either form. Software implementations for MIX and MMIX have been developed by Knuth and made freely available. Several versions of both emulators exist. MIX is a 1960s-style computer. It is superseded by MMIX, a newer modern computer architecture, a 64-bit RISC instruction set architecture (ISA). For MMIX, Knuth collaborated with the architects of the MIPS and Alpha ISAs.
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