In computer programming, the flat memory model is an approach to organizing memory address space. In this model, a computer application uses a single address space for both program code memory and data memory. This is in contrast to the Harvard architecture used in early computing history, or the segmented memory architecture used in the Intel 80x86 family of microprocessors. On 16-bit processors, a flat memory model yields a maximum combined code/data size of just 64 kibibytes. 32-bit models can access a maximum of 4 gibabytes, while 64-bit processors can theoretically access an address space of 16 exbabytes. Computer programming (often simply programming or coding) is the craft of writing a set of commands or instructions that can later be compiled and/or interpreted and then inherently transformed to an executable that an electronic machine can execute or run. Programming requires mainly logic, but has elements of science... To meet Wikipedias quality standards, this article or section may require cleanup. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... In communications, a code is a rule for converting a piece of information (for example, a letter, word, or phrase) into another form or representation, not necessarily of the same type. ... In general, data consist of propositions that reflect reality. ... The term Harvard architecture originally referred to computer architectures that used physically separate storage and signal pathways for their instructions and data (in contrast to the von Neumann architecture). ... Segmented memory is a methodology employed by computer programmers. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ... The title given to this article is incorrect due to technical limitations. ... Microprocessors, including an Intel 80486DX2 and an Intel 80386 A microprocessor (abbreviated as µP or uP) is an electronic computer central processing unit (CPU) made from miniaturized transistors and other circuit elements on a single semiconductor integrated circuit (IC) (aka microchip or just chip). ... In computer science, 16-bit is an adjective used to describe integers that are at most two bytes wide, or to describe CPU architectures based on registers, address buses, or data buses of that size. ... A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to... 32-bit is a term applied to processors, and computer architectures which manipulate the address and data in 32-bit chunks. ... In computing, a 64-bit component is one in which data are processed or stored in 64-bit units (words). ...

Advantage over Harvard architecture

The flat memory model offers the advantage of programming simplicity over the other models mentioned above. A memory address is always unambiguous in the flat memory model, referring to a well-defined memory location. In contrast, a memory address the Harvard architecture requires an additional qualifier to distinguish a code address from a data address. This means added bookkeeping complexity for the programmer. A programmer or software developer is someone who programs computers, that is, one who writes computer software. ...

Advantage over segmented model

A similar complexity issue exists with the segmented memory model, as implemented on the now ubiquitous Intel 80x86 family of microprocessors. The segmented model divides a large memory address space into smaller chunks (called segments) that can be accessed by giving each chunk a unique number, called a selector. In order to do this, a special segment register is used to select the segment you wish to use, then the selected segment is made to look like a normal flat piece of memory. Using this configuration, a 16-bit microprocessor can access up to 4 gibibytes of memory (65536 segments of 65536 bytes). However, in real mode the arrangement of a Segmented Memory Model is where a 16-bit (64 KiB) addressing space is overlapped every 16 bytes (called a paragraph) in order to create a 1 mebibyte total addressing space. Real mode (also called real address mode in Intels manuals) is an operating mode of 80286 and later x86-compatible CPUs. ... dyn and The_Decryptors retarded way of saying megabyte. ...

In protected mode the lower 3 bits of a selector are NOT part of the index. Instead the first 2 bits are the Requested Privilege Level (RPL) of the selector, and the third bit tells the processor which table to look up. If it is zero, the index is in the GDT and if it is one, it is in the current LDT. The processor first checks the Descriptor Privilege Level (DPL) of the accessed segment against both the Current Privilege Level (CPL) and the selector's RPL and faults on access violations. Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ... The acronym GDT can refer to: Global Descriptor Table, a data structure used in some computer processors manufactured by Intel Global distance test, a metric used in protein structure prediction for judging the similarity of multiple protein structures with the same amino acid sequence Greenwich Daylight Savings Time, the daylight... LDT means Local Descriptor Table Someone to write more about these tables. ... A general protection fault in the Intel x86 architecture is a fault indicating that a currently executing program has in some way violated the rules of the hardware on which it is running. ...

If not, the processor looks it up in whenever table the index it is in for the segment base, and if it is not found, it causes a fault. If it is found, it checks if the current operation done is allowed on the segment. If not it faults. If it is allowed, the processor adds the offset to the segment base to form a 24-bit or 32-bit physical address and performs the operation.

Note: Because the index is 13-bit, even in protected mode using a segmented memory model, if the maximum size of a segment is 64 KiB only 1 GiB of virtual memory can be accessed at one time (512 MiB global, 512 MiB local). According to the International Electrotechnical Commission a kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage. ... The term gib may refer to: a castrated male cat or ferret an abbreviation for gibibyte (GiB) or gibibit (Gib) an abbreviation for Gibraltar an abbreviation for gib board, an alternative term for drywall a soul patch[citation needed] the singular form of gibs, a term in first person shooters... The memory pages of the virtual address space seen by the process, may reside non-contiguously in primary, or even secondary storage. ... The three-letter acronym MIB may refer to any of several concepts: Management information base, a computing information repository used (for example) by SNMP In marbles, any marble, but esp. ...

The advantage of the flat memory model is that applications running in such a model, unlike applications running in a segmented memory model, do not have to switch segments to access additional code or data. Furthermore, manipulating memory and data can be achieved with far fewer internal registers, as shown in the new generation of RISC microprocessors. This drastically simplifies processor architecture from a manufacturing point of view, compiler construction from a tool developer's point of view, and programming complexity from a programmer's point of view. Reduced Instruction Set Computer (RISC), is a microprocessor CPU design philosophy that favors a smaller and simpler set of instructions that all take about the same amount of time to execute. ...

These simple benefits of the flat memory model have enabled microprocessors utilising the model to outperform microprocessors utilising segmented memory models where most other environmental factors (e.g. microprocessor clock speed and memory speed) are considered equal. Put another way, microprocessors utilising a flat memory model have often been shown to achieve equivalent performance of a processor utilising a segmented memory model despite the fact they are running slower clock speeds and have simpler (and cheaper) architectures. In synchronous digital electronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. ...