Segmented addressing probably originated with Burroughs.but I could be wrong.
Suppose you have a flat memory model, and a program starting at location 4000. Here I'll write some pseudocode assembly.
4000 load A with 20h
4002 jump to subroutine at 4006h
4005 return from subroutine
4006 load X with 512
4009 store A at location X
400A increment X
400B compare X to 1024
400E branch if not equal to 4009h
4010 return from subroutine
Now this code mentions an absolute address: 4006h, then address of the subroutine. (The other address is part of a branch, and probably stored as a relative offset.) Suppose we store this code on disk, and then later we read it in. If we read it in starting at location 4000h, we are fine. If we read it in elsewhere, we might have a problem.
Now suppose we have a timeshare system, and we want to page programs in and out, and manage memory for the system. We have a problem; we have to correct all the addresses of a program when it is read in. And we can't do that.
Programs often use "jump tables" to look up an address. How do we detect a jump table and correct the address? Further, suppose I *compute* an address. I might do this by taking a value and shifting it a few places. For example, I might have a lookup table for the sine of angles. The sine of angle X is stored as a four-byte floating-point value, starting at location 2000h. I compute the sine by reading the four bytes starting at 2000h + X<<2.
ADD EAX, 2000h
Now how do I correct this? There's no way to know that 2000h is a memory address, and not just some value that needs to be added to EAX for some other purpose.
Now suppose I have segmented addressing. I can now write my programs as if they started at location zero. I write all my programs that way, and the loader sets my segment correctly when the program is loaded. Now I don't have to worry about correcting addresses. I can load the program almost anywhere I want in memory, and adjust the segment registers accordingly. I can also have a segment for data and the stack, so that I can lay the program out in memory however I want.
Suppose I need 16K for the program, 8K for the stack, and 8K for data. If I don't have 32K of contiguous memory I can't load the program. However thanks to segmented addressing I can load the parts of the program into different areas.
Now, segmented addressing is falling out of favor. This is because people typically use assemblers and compilers that produce symbolic object code ready for a loader to resolve all symbols when the program is loaded. This is a more complicated process. Early segmented memory allowed loaders to be simpler, and made memory management possible.
Further, when you have a device such as a disk mapped to memory, you can just point the segment there and directly read and write from offset zero.
The 8085 does not have segment registers.
Registers in a microprocessor are utilized, even though the same operations can be done using RAM, in order to boost performance. Registers, although adding cost and complexity, are very much faster than RAM. Its a balance between performance and cost.
segment registers hold the starting address of the corresponding registers.By segmentation we can effectively utilize the memory. by segmentation we can make 8086 as multitasking environment.
In the 8086 microprocessor, the Code Segment (CS) register contains the paragraph address that will be added to the Instruction Pointer to obtain the address of the next instruction. Similarly, the Data Segment (DS) register contains the paragraph address that will be added to the Effective Address that is computed to find the address of the data used by that instruction. There are segment override prefixes, but the default use is CS for instructions and DS for data.'normal' address space in 8086 is 16 bit r which allows it to address 64k of linear memory space. Using segment registers to select a 'bank of memory' the CPU can use much more (20 bit addressing space)
One advantage of touch screen cash registers is that you do not have to learn how to type using home row keys. Another advantage of touch screen cash registers is that they're easy to use.
The physical address in the 8086/8088 is calculated by adding the effective address with the contents of one of the segment registers left shifted by 4 bit positions. This results in a 20 bit address bus. As an example, if the CS register contains 1234H, and the IP register contains 5678H, then the next instruction is fetched from physical address 179B8H, which is 1234H times 16 (12340H) plus 5678H. The segment register used is selected by context, or by using a segment override prefix, however, the code segment register (CS) can not be overidden during instruction fetch, nor can the stack segment register (SS) be overidden during stack pushes and pops.
There are four segment registers in the 8086/8088 processor, CS, DS, ES, and SS, also known as Code Segment, Data Segment, Extra Segment, and Stack Segment. Any time an address is generated by the processor, it is added to the value of one of the segment registers, after that segment register is effectively multiplied by 16, or left shifted four bits, in order to generate the physical address that accesses memory. This gives an effective address range of 20 bits, or 1mb, but note that only 64kb is addressable through any segment register at one time, unless you stop to change the contents of that segment register. This is known as a segmented architecture. By default, the CS register is used when fetching instructions, the DS register is used when accessing data, the SS register is used when accessing the stack, and the ES register is used during certain string type instructions. If desired, an instruction prefix can be used to override, such as forcing use of CS instead of DS when using a table contained within opcode space.
Registers hold small bits of information that the microprocessor may be using for a given task at any given time. Because of its small storage size and distance to the actual processor itself, it's extremely fast.
microprocessor is a programmable,clock-drive device.
Code segment (CS) is a 16-bit register containing address of 64 KB segment with processor instructions. The processor uses CS segment for all accesses to instructions referenced by instruction pointer (IP) register. CS register cannot be changed directly. The CS register is automatically updated during far jump, far call and far return instructions. Data segment (DS) is a 16-bit register containing address of 64KB segment with program data. By default, the processor assumes that all data referenced by general registers (AX, BX, CX, DX) and index register (SI, DI) is located in the data segment. DS register can be changed directly using POP and LDS instructions. Code segment (CS) is a 16-bit register containing address of 64 KB segment with processor instructions. The processor uses CS segment for all accesses to instructions referenced by instruction pointer (IP) register. CS register cannot be changed directly. The CS register is automatically updated during far jump, far call and far return instructions. Data segment (DS) is a 16-bit register containing address of 64KB segment with program data. By default, the processor assumes that all data referenced by general registers (AX, BX, CX, DX) and index register (SI, DI) is located in the data segment. DS register can be changed directly using POP and LDS instructions.
The data is held in a register. There may be many registers holding data. When new data is entered the old data in the register(s) is overwritten.
You really should forget about it; the segment-offset memory model of 8086 has been nothing but a pain since it was invented in 1978 (32 years before!)
we are using just one ic in a microprocessor
registers are a small high-speed memory inside CPU. one advantage of using them is increase in CPU speed because of their high access rate in comparison by ram.
The advantages to using the 64 bit version of Windows Vista include better performance and the ability to access more registers. One of the main disadvantages to using the 64 bit version of Windows Vista would be that data takes up more memory space than it normally would.
extra segment is a 16-bit register containing address of 64KB segment, usually with program data. By default, the processor assumes that the DI register points to the ES segment in string manipulation instructions. ES register can be changed directly using POP and LES instructions. It is possible to change default segments used by general and index registers by prefixing instructions with a CS, SS, DS or ES prefix. any corrections most welcome
A program which is used to count the number of numbers in an array using a 8085 microprocessor is known as a assembly language program.
The Intel 8080 was the first microprocessor using an 8 bit databus.
There are no advantages of using.
The 8051 is a microcontroller, not a microprocessor. To add or subtract, use the ADD or SUBB opcodes.
One many find this answer on YouTube. One also may find out how to write ascending order programs using an 8086 microprocessor by looking at the owners manual.
The segment had been taken off
Router enables communication across networks.Router can be used to segment Network that can restrict broadcast traffic within Subnet.
Multiplexed bus transfers different information at different well defined times through the same line. It advantages include, reduce physical/manufacturing complexity since fewer pins are used, and it prevent multiple device for competing for the same bus at the same time thus enhancing efficiency.