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Here, B0 means 'Move a copy of the following value into AL, and 61 is a hexadecimal representation of the value 01100001, which is 97 in decimal. Assembly language for the 8086 family provides the mnemonic MOV (an abbreviation of move) for instructions such as this, so the machine code above can be written as follows in assembly language, complete with an explanatory comment if required, after the semicolon. This is much easier to read and to remember.
Transforming assembly language into machine code is the job of an assembler, and the reverse can at least partially be achieved by a disassembler. Unlike high-level languages, there is a one-to-one correspondence between many simple assembly statements and machine language instructions. However, in some cases, an assembler may provide pseudoinstructions (essentially macros) which expand into several machine language instructions to provide commonly needed functionality. For example, for a machine that lacks a "branch if greater or equal" instruction, an assembler may provide a pseudoinstruction that expands to the machine's "set if less than" and "branch if zero (on the result of the set instruction)". Most full-featured assemblers also provide a rich macro language (discussed below) which is used by vendors and programmers to generate more complex code and data sequences. Since the information about pseudoinstructions and macros defined in the assembler environment is not present in the object program, a disassembler cannot reconstruct the macro and pseudoinstruction invocations but can only disassemble the actual machine instructions that the assembler generated from those abstract assembly-language entities. Likewise, since comments in the assembly language source file are ignored by the assembler and have no effect on the object code it generates, a disassembler is always completely unable to recover source comments.
Two examples of CPUs that have two different sets of mnemonics are the Intel 8080 family and the Intel 8086/8088. Because Intel claimed copyright on its assembly language mnemonics (on each page of their documentation published in the 1970s and early 1980s, at least), some companies that independently produced CPUs compatible with Intel instruction sets invented their own mnemonics. The Zilog Z80 CPU, an enhancement of the Intel 8080A, supports all the 8080A instructions plus many more; Zilog invented an entirely new assembly language, not only for the new instructions but also for all of the 8080A instructions. For example, where Intel uses the mnemonics MOV, MVI, LDA, STA, LXI, LDAX, STAX, LHLD, and SHLD for various data transfer instructions, the Z80 assembly language uses the mnemonic LD for all of them. A similar case is the NEC V20 and V30 CPUs, enhanced copies of the Intel 8086 and 8088, respectively. Like Zilog with the Z80, NEC invented new mnemonics for all of the 8086 and 8088 instructions, to avoid accusations of infringement of Intel's copyright. (It is questionable whether such copyrights can be valid, and later CPU companies such as AMD[nb 5] and Cyrix republished Intel's x86/IA-32 instruction mnemonics exactly with neither permission nor legal penalty.) It is doubtful whether in practice many people who programmed the V20 and V30 actually wrote in NEC's assembly language rather than Intel's; since any two assembly languages for the same instruction set architecture are isomorphic (somewhat like English and Pig Latin), there is no requirement to use a manufacturer's own published assembly language with that manufacturer's products.
Extended mnemonics are often used to support specialized uses of instructions, often for purposes not obvious from the instruction name. For example, many CPU's do not have an explicit NOP instruction, but do have instructions that can be used for the purpose. In 8086 CPUs the instruction xchg ax,ax is used for nop, with nop being a pseudo-opcode to encode the instruction xchg ax,ax. Some disassemblers recognize this and will decode the xchg ax,ax instruction as nop. Similarly, IBM assemblers for System/360 and System/370 use the extended mnemonics NOP and NOPR for BC and BCR with zero masks. For the SPARC architecture, these are known as synthetic instructions.
Assembly languages, like most other computer languages, allow comments to be added to program source code that will be ignored during assembly. Judicious commenting is essential in assembly language programs, as the meaning and purpose of a sequence of binary machine instructions can be difficult to determine. The "raw" (uncommented) assembly language generated by compilers or disassemblers is quite difficult to read when changes must be made.
If the output is larger than a certain threshold (default 1MiB), it will be presented to you as a file available for download. Slices of the file can be viewed in the output if you need to inspect them.
The rows in the mix output histograms come in two flavors. The rows that begin with "*" are meta-categories which sum up the data in different ways. Here are descriptions of some of the meta categories:*scalar-simd anything with the XED_ATTRIBUTE_SIMD_SCALAR including AVX and SSE operations. The instructions that operate on one vector element and whose iclass name ends with "SS" or "SD" have this attribute.*sse-scalar any SSE instruction with the XED_ATTRIBUTE_SIMD_SCALAR*sse-packed any SSE instruction without the XED_ATTRIBUTE_SIMD_SCALAR*avx-scalar Any AVX instruction with the attribute XED_ATTRIBUTE_SIMD_SCALAR*avx128 Any AVX instruction with a 128b vector length but without the XED_ATTRIBUTE_SIMD_SCALAR*avx256 Any AVX instruction with a 256b vector length*avx512 Any AVX instruction with a 512b vector length.*mem-atomic Atomic memory operations*stack-read Stack reads*stack-write Stack writes*iprel-read IP-relative memory reads*iprel-write IP-relative memory writes*mem-read-1 Memory read, 1 byte*mem-read-2 Memory read, 2 bytes*mem-read-4 Memory read, 4 bytes*mem-read-8 Memory read, 8 bytes*mem-write-1 Memory write, 1 byte*mem-write-2 Memory write, 2 bytes*mem-write-4 Memory write, 4 bytes*mem-write-8 Memory write, 8 bytes*isa-ext-BASE The "BASE" ISA-extension (generic group of instructions. Base includes much of the older instructions*isa-ext-LONGMODE The set of instructions added with Intel64. These may be 32b or 64b instructions*isa-set-I186 ISA "set" is a categorization of instructions in the BASE ISA-extension. I186 includes instructions introduced on the 80186 processor.*isa-set-I386 ISA "set" is a categorization of instructions in the BASE ISA-extension. I386 includes instructions introduced on the 80386 processor.*isa-set-I486REAL ISA "set" is a categorization of instructions in the BASE ISA-extension. I486REAL includes instructions introduced on the 80486 processor and valid in REAL mode.*isa-set-I86 ISA "set" is a categorization of instructions in the BASE ISA-extension. I86 includes instructions introduced on the 8086 processor.*isa-set-LONGMODE ISA "set" is a categorization of instructions in the LONGMODE ISA-extension. LONGMODE includes instructions introduced with Intel64 mode.*isa-set-PENTIUMREAL ISA "set" is a categorization of instructions in the BASE ISA-extension. PENTIUMREAL includes instructions introduced with Pentium and valid in REAL mode.*isa-set-PPRO ISA "set" is a categorization of instructions in the BASE ISA-extension. PPRO includes instructions introduced with the PentiumPro.*lock_prefix Instructions with a 0xF0 LOCK prefix*rep_prefix Instructions with a 0xF3 REP prefix*repne_prefix Instructions with a 0xF2 REPNE prefix*osz_prefix Instructions with a 0x66 prefix*rex_prefix Instructions with a REX prefix (includes the following 4 cases). REX prefixes can be sued without any of the following 4 bits set as well.*rexw_prefix Instructions with a REX prefix with the REX.W bit set*rexr_prefix Instructions with a REX prefix with the REX.R bit set*rexx_prefix Instructions with a REX prefix with the REX.X bit set*rexb_prefix Instructions with a REX prefix with the REX.B bit set*one-memops Instructions with one memory operation*two-memops Instructions with two memory operations*disp_only Instructions with a memory operation that addresses memory without using a base register or index register -- just a displacement.*base_index Instructions with a memory operation that addresses meory using a base and index register, but without a displacement.*base_index_disp Instructions with a memory operation that addresses memory using a base, index and displacement.*scale_1 Number of instructions with a scale=1 for the index register*scale_2 Number of instructions with a scale=2 for the index registern*scale_4 Number of instructions with a scale=4 for the index register*scale_8 Number of instructions with a scale=8 for the index register*memdisp8 Memory operations with 8-bit displacements*memdisp32 Memory operations with 32-bit displacements 2b1af7f3a8