assembly language

REGISTERRegister is a small piece of computer memory that is used to shelter the data provided that the data contained in the register can be processed in a variety of operations to see how much the ability to accommodate these registers.Registers can be divided into 5 categories, namely:A. General Purpose Register (Scratch-Pad Register), consisting of:• AX (AH + AL) = Accumulator Register• BX (BH + BL) = Base Register• CX (CH + CL) = Counter Register• DX (DH + DL) = Data Register2. Segment Register• CS = Code Segment Register• DS = Segment Data Register• SS = Stack Segment Register• ES = Extra Segment Register3. Pointer Register• IP = Instruction Pointer Register• SP = Stack Pointer Register• BP = Base Pointer Register4. Index Register• SI = Source Index Register• Destination Index DI = register5. Flag Register
 GENERAL PURPOSE REGISTERGeneral Purpose Register emapt fruit consists of (4) registers that have a full 16-bit and can be divided into Low and High Bits Register, each capable of 8 bits. Register AXAX register is the arithmetic registers, because registers are always used in the operations of addition, subtraction, multiplication and division.Each has a general purpose register Register Register Low and High, then for his low register AX tends to AL and its high registers are AH. Register AH is the place to put the service number for a particular interrupt. Register BXRegister BX is one of the two base register addressing modes that can pick up or write directly from / to memory. Register CXRegister CX is a counter to put the number of jumps in the Loop that you do. Register DXDX register has three tasks, namely: Assist AX in the process of multiplication and division, especially the 16 bit multiplication and division. register DX is offset from the DS DX indicates the port number on the charge of port operations
 memory addressing AND SEGMENT REGISTERWhen the memory is contained on the computer is 1 megabyte of memory space is:

00 00000 00100 00200 00300 004    .    .    .FFFF9FFFFAFFFFBFFFFCFFFFDFFFFEFFFFF
Addressing memory space on the image above is an absolute addressing with 20 bit capability. Whereas in 8088 capbility only up to 16 bits ,still lacks the means to accommodate a 4-bit memory address.Due to the above, then the numbering done by two registers. A register contains 16 bits counted from the right and the other 16 bits of the left.16-bit register that filling of the left called Segment Register and Register of fill from the right is a 16 bit Offset Register. Register contents are called Segment Segment and Offset Register contents are called Offset.Memory addressing is done the way the computer is often called the Relative Address. Examples of Absolute Relative Address and Address:
 A123: 099AComposition of Bit Segment 1010 0001 0010 0011 0000Bit Offset composition 0000 1001 1001 1010Absolute address 1010 0001 1011 1100 1010 (hex: A1BCA) 5674:9001Composition of Bit Segment 0101 0110 0111 0100 0000Bit Offset composition 1001 0000 0000 0001Absolute address 0101 1111 0111 0100 0001 (hex: 5F741)
 Register CSCS register is an important task is to show the program segment is located. This register pair is the IP register. Register DS and SSDS and SS registers task is to show a segment of the data segment and stack segment. DS is a pair of registers DX and SS registers are SP. Register ESThese registers do not have a job, but is useful for programming at the time of operation to another segment.
 POINTER REGISTERPointer Register duty to save the offset of the relative address. Register IPIP register is a register pair CS register which is important to demonstrate a command line program. In the first run the program this register will directly point at the beginning of the program. Register SPSP register pair is the SS register is used for stack operations. At the time of the first program executed this register will point to last byte stack. Register BPBP registers have functions similar to the BX register to write and read to or from memory directly.The difference is BX write and read the segment SS (Stack Segment).BP register is also used in communication anatara computer languages ​​such as PASCAL with Turbo C or Assembler Assembler.
 INDEX REGISTERRegister Index consists of two registers, namely DI and SI registers, wherein the second register is a register that is used to perform string operations. The second register is often used to write and read to or from memory such as BX and BP.
 FLAG REGISTER
X X X X O D I S T A Z X X P X C
Flag Bits:• O = Overflow Flag• D = Direction Flag• I = Interrupt Flag• T = Trap Flag• S = Sign Flag• Z = Zero Flag• A = Auxiliary Carry Flag• P = Parity Flag• C = Carry Flag• X = Reserved (empty)
Flag this register is a composition of 16-bit register with the provisions as shown above, wherein the composition bitnya can check whether something works or not.Example: Interrupt Flag to check whether an interrupt when the operation is active or not, if not active, the interrupt will not be executed.Carry Flag to check whether an error occurred during the operation or not. Sign Flag indicating whether a number is marked or not, and so on.