|
Address Constant
{{short description, Assembly language data type In IBM System/360 through present day z/Architecture, an address constant or "adcon" is an assembly language data type which contains the address of a location in computer memory. An address constant can be one, two, three or four bytes long, although an adcon of less than four bytes is conventionally used to hold an expression for a small integer such as a length, a relative address, or an index value, and does not represent an address at all. Address constants are defined using an assembler language "DC" statement. Other computer systems have similar facilities, although different names may be used. Types of address constants A adcons normally store a four byte relocatable address, however it is possible to specify the length of the constant. For example, AL1(stuff) defines a one-byte adcon, useful mainly for small constants with relocatable values. Other adcon types can similarly have length specification. V type adcons store a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM System/360
The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applications and a complete range of applications from small to large. The design distinguished between architecture and implementation, allowing IBM to release a suite of compatible designs at different prices. All but the only partially compatible Model 44 and the most expensive systems use microcode to implement the instruction set, featuring 8-bit byte addressing and fixed-point binary, fixed-point decimal and hexadecimal floating-point calculations. The System/360 family introduced IBM's Solid Logic Technology (SLT), which packed more transistors onto a circuit card, allowing more powerful but smaller computers. System/360's chief architect was Gene Amdahl, and the project was managed by Fred Brooks, responsible to Chairman Thomas J. Wat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Position-independent Code
In computing, position-independent code (PIC) or position-independent executable (PIE) is a body of machine code that executes properly regardless of its memory address. PIC is commonly used for shared libraries, so that the same library code can be loaded at a location in each program's address space where it does not overlap with other memory in use by, for example, other shared libraries. PIC was also used on older computer systems that lacked an MMU, so that the operating system could keep applications away from each other even within the single address space of an MMU-less system. Position-independent code can be executed at any memory address without modification. This differs from absolute code, which must be loaded at a specific location to function correctly, and load-time locatable (LTL) code, in which a linker or program loader modifies a program before execution, so it can be run only from a particular memory location. The latter terms are sometimes referred to as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primitive Types
In computer science, primitive data types are a set of basic data types from which all other data types are constructed. Specifically it often refers to the limited set of data representations in use by a particular processor, which all compiled programs must use. Most processors support a similar set of primitive data types, although the specific representations vary. More generally, ''primitive data types'' may refer to the standard data types built into a programming language (built-in types). Data types which are not primitive are referred to as ''derived'' or ''composite''. Primitive types are almost always value types, but composite types may also be value types. Common primitive data types The most common primitive types are those used and supported by computer hardware, such as integers of various sizes, floating-point numbers, and Boolean logical values. Operations on such types are usually quite efficient. Primitive data types which are native to the processor have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Types
In computer science and computer programming, a data type (or simply type) is a collection or grouping of data values, usually specified by a set of possible values, a set of allowed operations on these values, and/or a representation of these values as machine types. A data type specification in a program constrains the possible values that an expression, such as a variable or a function call, might take. On literal data, it tells the compiler or interpreter how the programmer intends to use the data. Most programming languages support basic data types of integer numbers (of varying sizes), floating-point numbers (which approximate real numbers), characters and Booleans. Concept A data type may be specified for many reasons: similarity, convenience, or to focus the attention. It is frequently a matter of good organization that aids the understanding of complex definitions. Almost all programming languages explicitly include the notion of data type, though the possible da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pointer (computer Programming)
In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer ''references'' a location in memory, and obtaining the value stored at that location is known as ''dereferencing'' the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture. Using pointers significantly improves performance for repetitive operations, like traversing iterable data structures (e.g. strings, lookup tables, control tables, linked lists, and tree structures). In particular, it is often much cheaper in time and space to copy and deref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relocation (computing)
In software development, relocation is the process of assigning load addresses for position-dependent code and data of a program and adjusting the code and data to reflect the assigned addresses. A linker usually performs relocation in conjunction with ''symbol resolution'', the process of searching files and libraries to replace symbolic references or names of libraries with actual usable addresses in memory before running a program. Relocation is typically done by the linker at link time, but it can also be done at load time by a relocating loader, or at run time by the running program itself. Segmentation Object files are typically segmented into various memory segment or section types. Example segment types include code segment (.text), initialized data segment (.data), uninitialized data segment (.bss), or others as established by the programmer, such as common segments, or named static segments. Relocation table The relocation table is a list of address ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM System Z
IBM Z is a family name used by IBM for all of its z/Architecture mainframe computers. In July 2017, with another generation of products, the official family was changed to IBM Z from IBM z Systems; the IBM Z family will soon include the newest model, the IBM z17, as well as the z16, z15, z14, and z13 (released under the IBM z Systems/IBM System z names), the IBM zEnterprise models (in common use the zEC12 and z196), the IBM System z10 models (in common use the z10 EC), the IBM System z9 models (in common use the z9EC) and ''IBM eServer zSeries'' models (in common use refers only to the z900 and z990 generations of mainframe). Architecture The ''zSeries,'' ''zEnterprise,'' ''System z'' and ''IBM Z'' families were named for their availability – ''z'' stands for High availability, zero downtime. The systems are built with spare components capable of hot failovers to ensure continuous operations. The IBM Z family maintains full backward compatibility. In effect, current system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TSS/360
The IBM Time Sharing System TSS/360 is a discontinued early time-sharing operating system designed exclusively for a special model of the System/360 line of mainframes, the Model 67. Made available on a trial basis to a limited set of customers in 1967, it was never officially released as a supported product by IBM. TSS pioneered a number of novel features, some of which later appeared in more popular systems such as MVS. TSS was migrated to System/370 and 303x systems, but despite its many advances and novel capabilities, TSS failed to meet expectations and was eventually canceled. The Resident Supervisor of TSS/370 was used as the basis for a port of UNIX to the IBM mainframe. TSS/360 also inspired the development of the TSS/8 operating system. Novel characteristics TSS/360 was one of the first implementations of tightly coupled symmetric multiprocessing. A pair of Model 67 mainframes shared a common physical memory space, and ran a single copy of the kernel (and applica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BOS/360
Basic Operating System/360 (BOS/360) was an early IBM System/360 operating system. Origin BOS was one of four System/360 Operating System versions developed by the IBM General Products Division (GPD) in Endicott, New York to fill a gap at the low end of the System/360 line when it became apparent that OS/360 was not able to run on the smallest systems. BPS (Basic Programming support) was designed to run on systems with a minimum of 8 KB of main storage and no disk. BOS was intended for disk systems with at least 8 KB and one 2311 disk drive. DOS and TOS were developed from BOS for systems with at least 16 KB and either disks (DOS) or tape drives only (TOS). BOS was released in October 1965, nearly two years before OS/360, thus BOS was the only disk based operating system available at launch for a machine that was marketed as disk based. Components BOS consisted of the following components: * Control programs: ** The supervisor. ** Job control capable of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Z/Architecture
z/Architecture, initially and briefly called ESA Modal Extensions (ESAME), is IBM's 64-bit complex instruction set computer (CISC) instruction set architecture, implemented by its mainframe computers. IBM introduced its first z/Architecture-based system, the z900, in late 2000. Subsequent z/Architecture systems include the IBM z800, z990, z890, System z9, System z10, zEnterprise 196, zEnterprise 114, zEC12, zBC12, z13, z14, z15, z16, and z17. z/Architecture retains backward compatibility with previous 32-bit-data/31-bit-addressing architecture ESA/390 and its predecessors back to the 32-bit-data/24-bit-addressing System/360. The IBM z13 is the last z Systems server to support running an operating system in ESA/390 architecture mode. However, all 24-bit and 31-bit problem-state application programs originally written to run on the ESA/390 architecture will be unaffected by this change. Features z/Architecture includes almost all of the features of ESA/390, and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DOS/360 And Successors
Disk Operating System/360, also DOS/360, or simply DOS, is the discontinued first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966. In its time, DOS/360 was the most widely used operating system in the world. DOS versions BOS/360 The Basic Operating System (BOS) was an early version of DOS and TOS which could provide usable functionality on a system with as little as 8 KB of main storage and one 2311 disk drive. TOS/360 TOS/360 (Tape Operating System/360, not a DOS as such and not so called) was an IBM operating system for the System/360, used in the early days around 1965 to support the System/360 Model 30 and similar platforms. TOS, as per the "Tape" in the name, required a tape drive. It shared most of the code base and some manuals with IBM's DOS/360. TOS went through 14 releases, and was discontinued when disks such as the IBM 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linker (computing)
A linker or link editor is a computer program that combines intermediate software build files such as object file, object and library (computing), library files into a single executable file such as a program or library. A linker is often part of a toolchain that includes a compiler and/or assembler (computing), assembler that generates intermediate files that the linker processes. The linker may be integrated with other toolchain development tool, tools such that the user does not interact with the linker directly. A simpler version that writes its Input/output, output directly to Computer memory, memory is called the ''loader'', though loader (computing), loading is typically considered a separate process. Overview Computer programs typically are composed of several parts or modules; these parts/modules do not need to be contained within a single object file, and in such cases refer to each other using symbol (computing), symbols as addresses into other modules, which are ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
