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Dynamic environment variables (also named internal variables or system information variables under DOS) are pseudo-environment variables supported by CMD.EXE when command-line extensions are enabled, and they expand to various discrete values whenever queried, that is, their values can change when queried multiple times even within the same ...
command.com running in a Windows console on Windows 95 (MS-DOS Prompt) COMMAND.COM is the default command-line interpreter for MS-DOS, Windows 95, Windows 98 and Windows Me. In the case of DOS, it is the default user interface as well. It has an additional role as the usual first program run after boot (init process).
Environment variables are a facility provided by some operating systems.Within the OS's shell (ksh in Unix, bash in Linux, COMMAND.COM in DOS and CMD.EXE in Windows) they are a kind of variable: for instance, in unix and related systems an ordinary variable becomes an environment variable when the export keyword is used.
In most computer file systems, every directory has an entry (usually named ".") which points to the directory itself.In most DOS and UNIX command shells, as well as in the Microsoft Windows command line interpreters cmd.exe and Windows PowerShell, the working directory can be changed by using the CD or CHDIR commands.
In the DOS era, it was customary to add a PATH {program directory}; %PATH% or SET PATH = {program directory}; %PATH% line to AUTOEXEC.BAT. When a command is entered in a command shell or a system call is made by a program to execute a program, the system first searches the current working directory and then searches the path, examining each ...
The initial design is encouraged to use the most restrictive visibility possible, in order of local (or method) variables, private variables (in object oriented programming), and global (or public) variables, and only be expanded when and as much as necessary. This prevents changes to visibility from invalidating existing code. [45]
Non-local variables are the primary reason it is difficult to support nested, anonymous, higher-order and thereby first-class functions in a programming language. If the nested function or functions are (mutually) recursive, it becomes hard for the compiler to know exactly where on the call stack the non-local variable was allocated, as the frame pointer only points to the local variable of ...
In Python, non-innermost-local and not-declared-global accessible names are all aliases. Among dynamically-typed languages, Python is moderately type-checked. Implicit conversion is defined for numeric types (as well as booleans), so one may validly multiply a complex number by an integer (for instance) without explicit casting.