The River Exe ( /ˈɛks/ EKS) in England rises near the village of Simonsbath, on Exmoor in Somerset, near the Bristol Channel coast, but flows more or less directly due south, so that most of its length lies in Devon. It reaches the sea at a substantial ria, the Exe Estuary, on the south (English Channel) coast of Devon. Historically, its lowest bridging point was at Exeter, though there is now a viaduct for the M5 motorway about 3 kilometres (2 mi) south of the city centre.

The river's name derives from the Celtic word Isca meaning, simply, water. The river gives its name to the city of Exeter and many other settlements along its course,^{[citation needed]} including Exford, Up Exe, Nether Exe, Exwick, Exton, Exminster, and Exebridge, where it is joined by the River Barle. The seaside town of Exmouth is at the east side of the estuary mouth, and Dawlish Warren is at the west, with its long sand spit extending across the mouth.

The river fuelled Exeter's growth and relative importance in medieval times, and the city's first industrial area was developed at Exe Island, created by a series of leats to the west of the city. The island was home to numerous watermills producing paper and textiles; it also created valuable land through drainage of the marshlands.

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, tributary and rill. There are no official definitions for generic terms, such as river, as applied to geographic features, although in some countries or communities a stream may be defined by its size. Many names for small rivers are specific to geographic location; one example is "burn" in Scotland and northeast England. Sometimes a river is said to be larger than a creek, but this is not always the case, because of vagueness in the language.

Rivers are part of the hydrological cycle. Water within a river is generally collected from precipitation through a drainage basin from surface runoff and other sources such as groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (e.g., from glaciers). Potamology is the scientific study of rivers.

EXE is the common filename extension denoting an executable file (a program) in the DOS, OpenVMS, Microsoft Windows, Symbian, and OS/2 operating systems. Besides the executable program, many EXE files contain other components called resources, such as bitmaps and icons which the executable program may use for its graphical user interface.

There are several main executable file formats:

Besides these, there are also many custom EXE formats, such as W3 (a collection of LE files, only used in WIN386.EXE), W4 (a compressed collection of LE files, only used in VMM32.VXD), DL, MP, P2, P3 (last three used by Phar Lap extenders), and probably more^{[citation needed]}.

When a 16-bit or 32-bit Windows executable is run by Windows, execution starts at either the NE or the PE, and ignores the MZ code. On the other hand, DOS cannot execute these files (except using HX DOS Extender, which supports PE files only). To prevent DOS from crashing, all Windows executable files should and usually do start with a "working" DOS program called a stub., simply displaying the message "This program cannot be run in DOS mode" (or similar) before exiting cleanly. A few dual-mode programs (MZ-NE or MZ-PE) (such as regedit and some older WinZIP self extractors^{[citation needed]}) include a more functional DOS section.