X86 assembly language - X86 assembly language Table of contents showTocToggle("show","hide") 1 x86 PC assembly tutorial 2 Basic information 3 Assembly in real mode 3..1 The mnemonics used in real mode x86-assembly 3..2 The real mode addressing model 3..3 the PC memory layout 3..4 Interrupts in real mode 3..5 Example code 4 Protected Mode x86 PC assembly tutorial This is a tutorial, not a complete scientific description of how the x86 processor works. This text is intended for those who want to gain a insight into programming real assembly language. Because the x86 processors are so common, most of you should be able to assemble most of the code that you find in this tutorial at your own computer. This tutorial uses standard Intel syntax, not AT&T syntax in which.
X86 - X86 x86 or Intel 80x86 is the generic name of an architecture of microprocessors first developed and manufactured by Intel. Introductrion x86 CPUss are also manufactured at various stages by AMD, Cyrix, NEC, IDT, Transmeta (that uses it in PDAs too, see Crusoe) (arguably) and sundry other makers at various stages in its nearly 25-year history. In addition to basic architecture itself, these names are also used to describe a family of particular microprocessors manufactured by Intel, including the Intel 8086, Intel 80186, Intel 80286, Intel 80386, Intel 80486, Pentium, Pentium Pro, Pentium II, Pentium III and Pentium 4. For marketing reasons, Intel refers to x86 processors as IA-32 while most of its competitors calls them x86. Intel's IA-64 architecture used in its Itanium processors is.
X86-jmp - X86-jmp check: do long jumps and near have 4 and 2 byte offset? "JMP" is a mnemonic used in x86 assembly language. unconditional jump (JuMP) to the address that follows, like this: JMP 0x89AB ; loads IP with the new value 0x89AB JMP 0xACDC:0x5578 ; loads CS with 0xACDC and IP with 0x5578 ; only works in real mode JMP 0x56789AB1 ; loads IP with the value 0x56789AB1 ; only works in protected mode We divide jump instructions into short jumps (one byte offset), near jumps (two byte offset?) long jumps (4bytes?) and far jumps (2 bytes segment / selector and full IP / EIP). JMP $ is commonly used to hang the computer. See also: conditional jumps..
IA-32 - instruction set is usually described as CISC (Complex Instruction Set Computer) architecture, though such classifications have become less meaningful over time. The set is implemented in all x86 CPUs newer than the 80386. IA-32 programs run in protected mode which has memory protection, the possibility to use memory above 640K (MS-DOS limit), virtual memory and multitasking. IA-32 programs can access a 4GB linear address space. Each generation of CPUs since has added several features to this set: The 80386 could accept an optional external coprocessor chip called the 80387 that enabled it to do floating point calculations via hardware. Some models of the 80486 had this coprocessor on-die. Pentium MMX added a set of extensions called MMX that can be used, among other things, to optimize multimedia software running on it..
IBM PC compatible - today. They are based (without IBM's participation) on the original IBM PC. They use the Intel x86 architecture and are capable of using interchangable commodity hardware. The origins of this platform came with the decision by IBM in 1981 to market a personal computer as quickly as possible in response to Apple Computer's rapid success (50% marketshare) in the burgeoning PC market. In licensing an operating system from Microsoft, IBM's agreements allowed Microsoft to sell MSDOS for non-IBM platforms (the IBM version was called PC-DOS). Also, in creating the platform, IBM used only one proprietary component: the BIOS. Columbia produced the first IBM PC compatible in 1982. Compaq Computer Corp produced an early IBM PC compatible a few months later in 1982. Compaq could not directly copy the BIOS as a.
Intel 8086 - chip designed by Intel in 1978, which gave rise to the x86 architecture. Shortly later the Intel 8088 was introduced with an external 8-bit bus, allowing the use of cheap chipsets. It was based on the design of the 8080 and 8085 (it was assembly language source-compatible with the 8080) with a similar register set, but was expanded to 16 bits. The Bus Interface Unit fed the instruction stream to the Execution Unit through a 6 byte prefetch queue, so fetch and execution were concurrent - a primitive form of pipelining (8086 instructions varied from 1 to 4 bytes). It featured four 16-bit general registers, which could also be accessed as eight 8-bit registers, and four 16-bit index registers (including the stack pointer). The data registers were often used implicitly by.
Hello world program - out "Hello, world!". It is used in many introductory tutorials for teaching a programming language and many students use it as their first programming experience in a language. A "hello world" program is typically one of the simpler programs possible in a computer language. Some are surprisingly complex, especially in some Graphical User Interface (GUI) contexts. Some others are surprisingly simple, especially those which heavily rely on a particular shell to perform the actual output. A "hello world" program can be a useful sanity test to make sure that a language's compiler, development environment, and run-time environment are correctly installed. Configuring a complete programming tool chain from scratch to the point where even trivial programs can be compiled and run may involve substantial amounts of work. For this reason, a simple.
High-level assembler - assembler High-level assemblers are assembly language translators that incorporate features found in modern high level languages into an assembler (compiler for an assembly language). Examples of high-level assemblers include Microsoft's MASM, Borland's TASM, and the High Level Assembler (HLA). HLA is a public-domain, open-source, system for processing high-level assembly language for the x86 processor. It current runs under Windows and Linux. It includes a massive library of subroutines (The HLA "Standard Library") and programs written in HLA are immediately portable between Windows and Linux with nothing more than a recompile. HLA has the most powerful macro and compile-time language facilities of any x86 assembler currently available. High level assemblers typically provide all the usual low-level machine instructions plus they add statements like IF, WHILE, REPEAT..UNTIL, FOR, etc., to the base language..
Embedded system - an embedded system often must run with real-time constraints. Usually there is no disk drive, operating system, keyboard or screen. There are many different CPU architectures used in embedded designs. This in contrast to the desktop computer market, which as of this writing (2003) is limited to just a few competing architectures, chiefly Intel's x86, and the Apple/Motorola/IBM PowerPC, used in the Apple Macintosh. One common configuration for embedded systems is the system on a chip, an application-specific integrated circuit, for which the CPU was purchased as intellectual property to add to the IC's design. The software tools (compilers, assemblers and debugger) used to develop an embedded system can come from several sources: Software companies that specialize in the embedded market Ported from the GNU software development tools Sometimes, development tools.
Assembler - Assembler An assembler is a computer program for translating assembly language — essentially, a mnemonic representation of machine language — into object code. A cross assembler (see cross compiler) produces code for one processor, but runs on another. As well as translating assembly instruction mnemonics into opcodes, assemblers provide the ability to use symbolic names for memory locations (saving tedious calculations and manually updating addresses when a program is slightly modified), and macro facilities for performing textual substitution — typically used to encode common short sequences of instructions to run inline instead of in a subroutine. Assemblers are far simpler to write than compilers for high-level languages, and have been available since the 1950s. Modern assemblers, especially for RISC based architectures, such as MIPS, Sun SPARC and HP PA-RISC, optimize instruction.
Compiler optimization - original code. Table of contents showTocToggle("show","hide") 1 Problems with Optimization 2 Types of Optimizations 3 Factors affecting optimization 4 Intended use of the generated code 5 Optimization techniques 5.1 Common Themes 5.2 Optimization techniques 5.2.1 Loop Optimizations 5.2.2 Data-flow Optimizations 5.2.3 SSA-based Optimizations 5.2.4 Back End Optimizations 5.2.5 Functional Language Optimizations 5.2.6 Other Optimizations 6 Links Problems with Optimization Further problems with optimizing compilers are: Usually, an optimizing compiler simply takes the intermediate representation of a program code and replaces it with a better version. In other words, high-level redundancy in the source program (such as an inefficient algorithm) remains unchanged. Modern third-party compilers usually have to support several objectives. In so doing, these compilers are the jack of all trades yet the master of none. A compiler typically only deals.
Xor swap algorithm - the symmetric difference property of XOR, that A xor A = 0 for every A Table of contents showTocToggle("show","hide") 1 The algorithm 2 Explanation 3 Code examples 3.1 x86 assembly language 3.2 Visual Basic 3.3 C 4 Usage in practice The algorithm Standard swapping algorithms require the use of a temporary storage area - standard intuitive algorithms to swap x and y involve: copying y aside to a temporary storage area setting y to be x copying the temporary storage value back to x. However, the XOR swap algorithm does not -- this algorithm follows (where X and Y are the names of two variables, rather than two values): XOR X and Y and store in X XOR X and Y and store in Y XOR X and Y and store in X.
Shellcode - patterns (often a large array of no-operating codes, or simply NOP's); if it finds any such pattern the packet is discarded before it reaches its destination application. The IDS's weak point is that it cannot do any really good searches as it takes too much time and would thereby slow down the connection to the Internet. Shellcode almost always contains a string with the name of a shell. All incoming packets containing such a string are undoubtedly quite suspicious in the eyes of the IDS. Also, some applications do not accept non-alphanumeric inputs (they do not accept anything other than a-z, A-Z, 0-9, and a few other characters.) To get trough such kinds of anti-intrusion measures, crackers sometimes make use of encryption, self-modifying code, polymorphic code and alphanumeric code. Outside links.
Real mode - (MS-Windows) operates in this mode. The advantage of using the real mode is that the BIOS routines may be used. Real mode is the only mode x86 processor designs were capable of operating in until the 80286. Other more modern operating systems switch to the more powerful protected mode. Read on: IA-32, X86 and x86 assembly language.
RISC - take about the same amount of time to execute. Most types of modern microprocessors are RISCs, for instance SPARC, MIPS, and PowerPC. The most widely-used type of microprocessor, the x86, is CISC rather than RISC, although the internal design of newer x86 family members is said to be RISC-like. The idea was inspired by the discovery that many of the features that were included in traditional CPU designs for speed were being ignored by the programs that were running on them. In addition, the speed of the CPU in relation to the memory it accessed was increasing. This led to a number of techniques to streamline processing within the CPU, while at the same time attempting to reduce the total number of memory accesses. More modern terminology refers to these designs.
Pentium FDIV bug - small amount. This result was quickly verified by other people around the Internet, and became known as the Pentium FDIV bug (FDIV is the x86 assembly language instruction for floating point division). Other people found division problems where the result returned by the Pentium was off by up to 61 parts per million. Note that this problem occurred only on some models of the original Pentium processor. Any Pentium family processor with a clock speed greater than 100 MHz is new enough not to have this bug. This report stirred up a huge controversy. Intel at first denied that the problem existed. Later, Intel claimed that it was not serious and would not affect most users; however, if you could prove that you were affected, Intel would replace your processor. However,.
OS-9 - general purpose computing and in embedded systems. The first version ("level one") was written in assembly language for the Motorola 6809 CPU, and provides a single 64KB address space in which all processes ran. A later 6809 version ("level two") takes advantage of memory mapping hardware, supported up to 1MB of memory (ca 1980!) in most implementations, included a GUI on some platforms, and so on. Later, OS-9/6809 was ported to Motorola 68000 assembly language and extended (called OS-9/68K); and a still later version was rewritten mostly in C for further portability. (The portable version was initially called OS-9000.) These later versions lack the memory mapping facilities of OS-9/6809 Level Two, nor did they need them. They used a single flat address space that all processes share; memory mapping hardware, if.
Linux kernel - with Unix. It was developed initially for the Intel 80386 processor but has since been ported to many other platforms. It is written almost entirely in C with some GNU C language extensions and assembly language. Table of contents showTocToggle("show","hide") 1 History 2 Architecture 3 Portability 4 Licensing terms 5 References 6 Resources History The project was launched in 1991 with a famous post to the Usenet newsgroup comp.os.minix that includes this sentence: "I\'m doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones..." The complete post can be found here. At the time, the GNU project had created many of the components required for a free operating system, but its own kernel, the Hurd, was conspicuously incomplete and unavailable. The BSD.
List of computing topics - do update the page accordingly. At the end is a list of important computer people. See also List of programmers. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Symbols/Numbers 1.TR.6 -- 100BaseFX -- 100BaseTX -- 100BaseT -- 100BaseVG -- 100VG-AnyLAN -- 10base2 -- 10base5 -- 10baseT -- 120 reset -- 16-bit -- 16-bit application -- 16550 UART -- 1NF -- 1TBS -- 2.PAK -- 20-Gate programming language -- 20-GATE -- 28-bit -- 2B1D -- 2B1Q -- 2D -- 2NF -- 3-tier (computing) -- 32-bit application -- 32-bit -- 320xx microprocessor -- 320xx -- 386BSD -- 386SPART.PAR -- 3Com Corporation -- 3DO -- 3D -- 3GL -- 3NF -- 3Station -- 4.2BSD -- 404.
Assembly language - Assembly language Assembly is a human-readable notation for the machine language that a specific computer architecture uses. Machine language, a mere pattern of bits, is made readable by replacing the raw values with symbols called mnemonics. So, while a computer will recognize what the IA-32 machine instruction 10110000 01100001 does, for programmers it is easier to remember the equivalent assembly language representation mov %al,$0x61 (it means to move the hexadecimal value 61 (97 decimal) into the register 'al'.) Unlike in high-level languages, there is (to a close approximation) a 1-to-1 correspondence between simple assembly and machine language. Transforming assembly into machine languages is accomplished by an assembler, the other direction by a disassembler. Every computer architecture has its own machine language, and therefore its own assembly.
