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C-list (computer Security)
In capability-based computer security, a C-list is an array of capabilities, usually associated with a process and maintained by the kernel. The program running in the process does not manipulate capabilities directly, but refers to them via C-list indexes—integers indexing into the C-list. The file descriptor table in Unix is an example of a C-list. Unix processes do not manipulate file descriptors directly, but refer to them via file descriptor numbers, which are C-list indexes. In the KeyKOS and EROS operating systems, a process's capability registers constitute a C-list. See also * Access-control list In computer security, an access-control list (ACL) is a list of permissions associated with a system resource (object or facility). An ACL specifies which users or system processes are granted access to resources, as well as what operations are al ... References {{Object-capability security Arrays Operating system security ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object-capability Model
The object-capability model is a computer security model. A capability describes a transferable right to perform one (or more) operations on a given object. It can be obtained by the following combination: :* An unforgeable reference (in the sense of object references or protected pointers) that can be sent in messages. :* A message that specifies the operation to be performed. The security model relies on not being able to forge references. :* Objects can interact only by sending messages on references. :* A reference can be obtained by: ::# Initial conditions: In the initial state of the computational world being described, object A may already have a reference to object B. ::# Parenthood: If A creates B, at that moment A obtains the only reference to the newly created B. ::# Endowment: If A creates B, B is born with that subset of A's references with which A chose to endow it. ::# Introduction: If A has references to both B and C, A can send to B a message containing a refer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Array (data Structure)
In computer science, an array is a data structure consisting of a collection of ''elements'' (value (computer science), values or variable (programming), variables), of same memory size, each identified by at least one ''array index'' or ''key'', a collection of which may be a tuple, known as an index tuple. An array is stored such that the position (memory address) of each element can be computed from its index tuple by a mathematical formula. The simplest type of data structure is a linear array, also called a one-dimensional array. For example, an array of ten 32-bit (4-byte) integer variables, with indices 0 through 9, may be stored as ten Word (data type), words at memory addresses 2000, 2004, 2008, ..., 2036, (in hexadecimal: 0x7D0, 0x7D4, 0x7D8, ..., 0x7F4) so that the element with index ''i'' has the address 2000 + (''i'' × 4). The memory address of the first element of an array is called first address, foundation address, or base address. Because the mathematical conc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Process (computing)
In computing, a process is the Instance (computer science), instance of a computer program that is being executed by one or many thread (computing), threads. There are many different process models, some of which are light weight, but almost all processes (even entire virtual machines) are rooted in an operating system (OS) process which comprises the program code, assigned system resources, physical and logical access permissions, and data structures to initiate, control and coordinate execution activity. Depending on the OS, a process may be made up of multiple threads of execution that execute instructions Concurrency (computer science), concurrently. While a computer program is a passive collection of Instruction set, instructions typically stored in a file on disk, a process is the execution of those instructions after being loaded from the disk into memory. Several processes may be associated with the same program; for example, opening up several instances of the same progra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kernel (operating System)
A kernel is a computer program at the core of a computer's operating system that always has complete control over everything in the system. The kernel is also responsible for preventing and mitigating conflicts between different processes. It is the portion of the operating system code that is always resident in memory and facilitates interactions between hardware and software components. A full kernel controls all hardware resources (e.g. I/O, memory, cryptography) via device drivers, arbitrates conflicts between processes concerning such resources, and optimizes the use of common resources, such as CPU, cache, file systems, and network sockets. On most systems, the kernel is one of the first programs loaded on startup (after the bootloader). It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit. The critical code of the kernel is usua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File Descriptor
In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typically have non-negative integer values, with negative values being reserved to indicate "no value" or error conditions. File descriptors are a part of the POSIX API. Each Unix process (except perhaps daemons) should have three standard POSIX file descriptors, corresponding to the three standard streams: Overview In the traditional implementation of Unix, file descriptors index into a per-process maintained by the kernel, that in turn indexes into a system-wide table of files opened by all processes, called the . This table records the ''mode'' with which the file (or other resource) has been opened: for reading, writing, appending, and possibly other modes. It also indexes into a third table called the inode table that describes the ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley ( BSD), Microsoft (Xenix), Sun Microsystems ( SunOS/ Solaris), HP/ HPE ( HP-UX), and IBM ( AIX). The early versions of Unix—which are retrospectively referred to as " Research Unix"—ran on computers such as the PDP-11 and VAX; Unix was commonly used on minicomputers and mainframes from the 1970s onwards. It distinguished itself from its predecessors as the first portable operating system: almost the entire operating system is written in the C programming language (in 1973), which allows U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KeyKOS
KeyKOS is a persistent, pure capability-based operating system for the IBM S/370 mainframe computers. It allows emulating the environments of VM, MVS, and Portable Operating System Interface (POSIX). It is a predecessor of the Extremely Reliable Operating System (EROS), and its successor operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...s, CapROS, and Coyotos. KeyKOS is a nanokernel-based operating system. In the mid-1970s, development of KeyKOS began at Tymshare, Inc., under the name GNOSIS. In 1984, McDonnell Douglas (MD) bought Tymshare. A year later MD spun off Key Logic, which bought GNOSIS and renamed it ''KeyKOS''. References External links * , Norman Hardy GNOSIS: A Prototype Operating System for the 1990s a 1979 paper, Tymshare Inc. a 1988 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EROS (microkernel)
Extremely Reliable Operating System (EROS) is an operating system developed starting in 1991 at the University of Pennsylvania, and then Johns Hopkins University, and The EROS Group, LLC. Features include automatic data and process persistence, some preliminary real-time support, and capability-based security. EROS is purely a research operating system, and was never deployed in real world use. , development stopped in favor of a successor system, CapROS. Key concepts The overriding goal of the EROS system (and its relatives) is to provide strong support at the operating system level for the efficient restructuring of critical applications into small communicating components. Each component can communicate with the others only through protected interfaces, and is isolated from the rest of the system. A ''protected interface'', in this context, is one that is enforced by the lowest level part of the operating system, the kernel. That is the only part of the system that can move info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Access-control List
In computer security, an access-control list (ACL) is a list of permissions associated with a system resource (object or facility). An ACL specifies which users or system processes are granted access to resources, as well as what operations are allowed on given resources. Each entry in a typical ACL specifies a subject and an operation. For instance, * If a file object has an ACL that contains, this would give Alice permission to read and write the file and give Bob permission only to read it. * If the Resource Access Control Facility (RACF) profile CONSOLE CLASS(TSOAUTH) has an ACL that contains, this would give ALICE permission to use the TSO CONSOLE command. Implementations Many kinds of operating systems implement ACLs or have a historical implementation; the first implementation of ACLs was in the filesystem of Multics in 1965. Filesystem ACLs A filesystem ACL is a data structure (usually a table) containing entries that specify individual user or group rights to spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arrays
An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the sums of their horizontal segments form a succession of twelve-tone aggregates * Array mbira, a musical instrument * Spiral array model, a music pitch space Science Astronomy A telescope array, also called astronomical interferometer. Biology * Various kinds of multiple biological arrays called microarrays * Visual feature array, a model for the visual cortex Computer science Generally, a collection of same type data items that can be selected by indices computed at run-time, including: * Array (data structure), an arrangement of items at equally spaced addresses in computer memory * Array (data type), used in a programming language to specify a variable that can be indexed * Associative array, an abstract data structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
