The  also called iAPX 86  is a bit microprocessor chip designed by Intel between early and June 8,when it was released. The Intelreleased July 1, is a slightly modified chip with an external 8-bit data bus allowing the use of cheaper and fewer supporting ICs[note 1] and is notable as the processor used in the original IBM PC design.
The gave rise to the x86 architecturewhich eventually became Intel's most successful line of processors. InIntel launched thethe first 8-bit microprocessor. The device needed several additional ICs to produce a functional computer, in part due to it being packaged in a small pin "memory package", which ruled out the use of a separate address bus Intel was primarily a DRAM manufacturer at the time.
Two years later, Intel launched the[note 3] employing the new pin DIL packages originally developed for calculator ICs to enable a separate address bus. It has an extended instruction set that is source-compatible not binary compatible with the  and also includes some bit instructions to make programming easier.
The project started in May and was originally intended as a temporary substitute for the ambitious and delayed iAPX project. It was an attempt to draw attention from the less-delayed and bit processors of other manufacturers such as MotorolaZilogand National Semiconductor and at the same time to counter the threat from the Zilog Z80 designed by former Intel employeeswhich became very successful.
Both the architecture and the physical chip were therefore developed rather quickly by a small group of people, and using the same basic microarchitecture elements and physical implementation techniques as employed for the slightly older and for which the also would function as a continuation. Marketed as source compatible the was designed to allow assembly language for the [ citation needed ], or to be automatically converted into equivalent suboptimal source code, with little or no hand-editing.
The programming model and instruction set is loosely based on the in order to make this possible. However, the design was expanded to support full bit processing, instead of the fairly limited bit capabilities of the and According to principal architect Stephen P. Morsethis was a result of a more software-centric approach than in the design of earlier Intel processors the designers had experience working with compiler implementations. Other enhancements included microcoded multiply and divide instructions and a bus structure better adapted to future coprocessors such as and and multiprocessor systems.
The architecture was defined by Stephen P.
Morse with some help and assistance by Bruce Ravenel the architect of the in refining the final revisions. Logic designer Jim McKevitt and John Bayliss were the lead engineers of the hardware-level development team [note 10] and Bill Pohlman the manager for the project.Lecture 15: Loop, Label, Inc and Program to print 0 to 9 in assembly language in urdu hindi
The legacy of the is enduring in the basic instruction set of today's personal computers and servers; the also lent its last two digits to later extended versions of the design, such as the Intel and the Intelall of which eventually became known as the x86 family. This address space is addressed by means of internal memory "segmentation".
The data bus is multiplexed with the address bus in order to fit all of the control lines into a standard pin dual in-line package. Some of the control pins, which carry essential signals for all external operations, have more than one function depending upon whether the device is operated in min or max mode. The former mode is intended for small single-processor systems, while the latter is for medium or large systems using more than one processor a kind of multiprocessor mode.
Assembly - Loops
Maximum mode is required when using an or coprocessor. Changing the state of pin 33 changes the function of certain other pins, most of which have to do with how the CPU handles the local bus.
The workings of these modes are described in terms of timing diagrams in Intel datasheets and manuals. In minimum mode, all control signals are generated by the itself. The has eight more or less general bit registers including the stack pointer but excluding the instruction pointer, flag register and segment registers.
Due to a compact encoding inspired by 8-bit processors, most instructions are one-address or two-address operations, which means that the result is stored in one of the operands. At most one of the operands can be in memory, but this memory operand can also be the destinationwhile the other operand, the sourcecan be either register or immediate.
A single memory location can also often be used as both source and destination which, among other factors, further contributes to a code density comparable to and often better than most eight-bit machines at the time. The degree of generality of most registers are much greater than in the or However, registers were more specialized than in most contemporary minicomputers and are also used implicitly by some instructions.
While perfectly sensible for the assembly programmer, this makes register allocation for compilers more complicated compared to more orthogonal bit and bit processors of the time such as the PDPVAX, etc. On the other hand, being more regular than the rather minimalistic but ubiquitous 8-bit microprocessors such as the, MCS, and other contemporary accumulator-based machines, it is significantly easier to construct an efficient code generator for the architecture.
Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Does loop jump or fall-through in that case? Or in bit code, it normally uses CX, but an address-size prefix 0x67 will make it use ecx. As Intel's manual says, it ignores REX. W, because that sets the operand-size, not the address-size.
Related: Why are loops always compiled into "do If you ever want to know the details on an instruction, check the manual: either Intel's official vol.
But note that the HTML leaves out the intro and appendices that have details on how to interpret stuff, like when it says "flags are set according to the result" for instructions like add. And you can and should also just try stuff in a debugger: single-step and watch registers change. See also the x86 tag wiki for links to manuals, guides, and asm debugging tips at the bottom. And BTW, if the instructions inside the loop that aren't shown modify ecxit could loop any number of times.
For the question to have a simple and unique answer, you need a guarantee that the instructions between the label and the loop instruction don't modify ecx. Rant about over-use of LOOP even when you already need to increment something else in the loop. LOOP isn't the only way to loop, and usually it's the worst. You should normally never use the loop instruction unless optimizing for code-size at the expense of speed, because it's slow.
Compilers don't use it. So CPU vendors don't bother to make it fast; catch Loops don't even have to use a counter; it's often just as good if not better to compare a pointer to an end address, or to check for some other condition. Pointless use of loop is one of my pet peeves, especially when you already have something in another register that would work as a loop counter.
IMO, loop should be considered one of those obscure x86 instructions that beginners shouldn't be distracted with. Like stosd without a rep prefixaam or xlatb. It does have real uses when optimizing for code size, though. That's sometimes useful in real life for machine code like for boot sectorsnot just for stuff like code golf. Then you won't get stuck into thinking there's something special about a loop that uses loop. I've seen an SO question or comment that said something like "I thought you had to declare loops", and didn't realize that loop was just an instruction.
Like I said, loop is one of my pet peeves. It's an obscure code-golfing instruction, unless you're optimizing for an actual Learn more. How exactly does the x86 LOOP instruction work?A label can be placed at the beginning of a statement. During assembly, the label is assigned the current value of the active location counter and serves as an instruction operand.
There are two types of lables: symbolic and numeric. Symbolic labels must be defined only once. Symbolic labels have global scope and appear in the object file's symbol table. Symbolic labels with identifiers beginning with a period. ASCII 0x2E are considered to have local scope and are not included in the object file's symbol table.
A numeric label consists of a single digit in the range zero 0 through nine 9 followed by a colon :. Numeric labels are used only for local reference and are not included in the object file's symbol table. Numeric labels have limited scope and can be redefined repeatedly. For numeric label Nthe reference N b refers to the nearest label N defined before the reference, and the reference N f refers to the nearest label N defined after the reference.
The following example illustrates the use of numeric labels:. Previous : Comments Next : Tokens. Labels A label can be placed at the beginning of a statement. Numeric Labels A numeric label consists of a single digit in the range zero 0 through nine 9 followed by a colon :.The following table provides a list of xAssembler mnemonics, that is not complete. Most of them can be found, for others see at www. The high order nibble is zeroed. Multiplies AH by 10 and the adds result into AL.
Sets AH to zero. This instruction is also known to have an undocumented behavior. The high order nibble of each byte must be zeroed before using this instruction. High order nibble is zeroed. If CF is set, a 1 is added to the destination. Both operands are binary. Otherwise the Zero Flag is cleared.
Microprocessor - 8086 Instruction Sets
Interrupt 5 occurs if the source value is less than or higher than the source. Sets ZF if a bit is found set and loads the destination with an index to first set bit. Clears ZF is no bits are found set. Result left in destination register is undefined if the operand is a 16 bit register. Code continues with execution at CS:IP.
NMI's and software interrupts are not inhibited. This is a privileged operation and is generally used only by operating system code. Flags can subsequently be checked for conditions.
Updates flags based on the subtraction and the index registers E SI and E DI are incremented or decremented depending on the state of the Direction Flag. The REP prefixes can be used to process entire data items.
If equal the "dest" is loaded with "src", otherwise the accumulator is loaded with "dest".Posted on Oktober 25, Tanda directive ini digunakan untuk memberitahukan kepada assembler bentuk memory yang digunakan oleh program kita. Supaya lebih jelas model-model yang bisa digunakan adalah :. Jika program anda hanya menggunakan 1 segment seperti program COM. Model ini disediakan khusus untuk program COM.
Jika data yang digunakan oleh program kurang dari 64 KB tetapi code yang digunakan bisa lebih dari 64 KB. Hal ini disebabkan karena banyak dari compiler bahasa tingkat tinggi yang tidak bisa berkomunikasi dengan model TINY, sehingga kita menggunakan model SMALL sebagai pemecahannya.
Tanda directive ini digunakan untuk memberitahukan kepada assembler bahwa kita akan mulai menggunakan Code Segment-nya disini. Code segment ini digunakan untuk menyimpan program yang nantinya akan dijalankan. Pada program COM perintah ini akan selalu digunakan. Perintah ini digunakan untuk memberitahukan assembler supaya program pada saat dijalankan diload ke memory ditaruh mulai pada offset ke h byte. Dapat dikatakan juga bahwa kita menyediakan h byte kosong pada saat program dijalankan.
Adapun syntaxnya adalah:. Dimana tujuannya dapat berupa label seperti yang digunakan pada bagan diatas. Mengenai perintah JUMP ini akan kita bahas lebih lanjut nantinya. Perintah JUMP yang digunakan pada bagan diatas dimaksudkan agar melewati tempat data program, karena jika tidak ada perintah JUMP ini maka data program akan ikut dieksekusi sehingga kemungkinan besar akan menyebabkan program anda menjadi Hang.
Interupsi 20h berfungsi untuk mengakhiri program dan menyerahkan kendali sepenuhnya kepada Dos. Pada program COM cara ini bukanlah satu-satunya tetapi cara inilah yang paling efektif untuk digunakan.
Bila anda lupa untuk mengakhiri sebuah program maka program anda tidak akan tahu kapan harus selesai, hal ini akan menyebabkan komputer menjadi hang. Bila anda menetapkan nilai CX menjadi nol pada saat pertama kali sebelum dilakukan loop, maka anda akan mendapatkan proses looping yang terbanyak.
Hal ini dikarenakan proses pengurangan 0 dengan 1 akan menghasilkan nilai FFFFh -1. Mungkin ada yang bertanya-tanya, apa yang akan terjadi bila Tujuan tempat hasil penjumlahan disimpan tidak mencukupi seperti pertambahan h dengan Fh. This entry was posted in Uncategorized. You are commenting using your WordPress. You are commenting using your Google account.
You are commenting using your Twitter account. You are commenting using your Facebook account. Beri tahu saya komentar baru melalui email. Beritahu saya pos-pos baru lewat surat elektronik. CODE Tanda directive ini digunakan untuk memberitahukan kepada assembler bahwa kita akan mulai menggunakan Code Segment-nya disini. INT 20 h ; Selesai!
INT 20h ; Selesai! Menyukai ini: Suka Memuat Tinggalkan Balasan Batalkan balasan Ketikkan komentar di sini Isikan data di bawah atau klik salah satu ikon untuk log in:. E-mail wajib Alamat takkan pernah dipublikasikan.Try using a label that starts with a letter and see if that works. I tried code like your and Jim's which icc and gcc would compile but would segfault at the jmp.
Swapping 1: for label1: fixed that for me. For reference, here is the code I compiled:. All rights reserved. For reference, that address in that call instruction is in no-mans land. Of course, some restrictions are possible complexity of codes dependant but at least the Test-case 2 works. Interesting differences between platforms. As far as i know on windows inline asm is assembled by icc and on linux inline asm is assmebled by "as" the GNU assembler.
Thanks guys for the replies Quote: Sergey Kostrov wrote:. As noted in my earlier post, differences in assembling inline asm between platforms is causing confusion with examples working for some but not all. It has already been established by Jim that the code I posted does not work in windows, but the intel compiler in linux will compile and it does work there.
Elbert, am I correct? Consider following snippet:. ICC choackes with error saying jumps in inline assembly is not implemented. At premier support they told me it will not be implemented at least in near future.
Quote: Casey wrote:. ICC chokes with error saying jumps in inline assembly is not implemented. GCC does not have any problem with this snippet. I realized from the beginning that the windows compiler was being used and had no intentions of having someone switch platforms.
I posted my test case which works purely to contribute to the thread. It was not until Jim's followup post to me that I did some digging and learned that the handling of inline assembly is different between windows and linux, making the test case platform specific -- knowledge of which I also contributed to this thread. There aren't too many issues where the platform is going to matter but this indeed is one of them. Thank you everyone for the posts. It is of great help to me.Post a Comment.
Copy a byte or word from accumulator to specified port number First operand is a port number. If required to access port number over - DX register should be used. Load effective address of operand into specified register. Add specified byte to byte or specified word to word. Subtract specified byte from byte or specified word from word.
Divides an unsigned dividend accumulator by an unsigned divisor register. Compare two specified bytes or two specified words. Decimal adjust After Addition.
X86 Assembly/Control Flow
Corrects the result of addition of two packed BCD values Algorithm:. It works according to the following Algorithm:. Rotate operand1 left through Carry Flag. The number of rotates is set by operand2. Rotate operand1 right through Carry Flag.
Algorithm: shift all bits left, the bit that goes off is set to CF and previous value of CF is inserted to the right-most position. Algorithm: shift all bits right, the bit that goes off is set to CF and previous value of CF is inserted to the left-most position. Rotate operand1 left. Rotate operand1 right. Algorithm: shift all bits left, the bit that goes off is set to CF and the same bit is inserted to the right-most position. Algorithm: shift all bits right, the bit that goes off is set to CF and the same bit is inserted to the left-most position.
Shift operand1 Left. The number of shifts is set by operand2. Shift operand1 Right. MOV AL, b. Call a procedure subprogramsave return address on stack. Returns from a procedure previously entered by a call. Like in E.