Ambient pressure concept of pressure becomes irrelevant, and it is undefined at a gravitational singularity. The SI unit of pressure is the pascal (Pa), which is a very small unit relative to atmospheric pressure on Earth, so kilopascals (kPa) are more commonly used in this context. The ambient atmospheric pressure at sea level is not constant: it varies with the weather, but averages around 100 kPa. In fields such as meteorology and underwater diving, it is common to see ambient pressure expressed in bar or millibar. One bar is 100 kPa or approximately ambient pressure at sea level. Ambient pressure may in
Pascal (programming language) R. Hoare. Pascal programs start with the program keyword with a list of external file descriptors as parameters<ref name="iso/iec 7185:1990 6.10">Pascal ISO 7185:1990 6.10</ref> (not required in Turbo Pascal etc.); then follows the main block bracketed by the begin and end keywords. Semicolons separate statements, and the full stop (i.e., a period) ends the whole program (or "unit"). Letter case is ignored in Pascal source. Here is an example of the source code in use for a very simple "Hello world" program: A type in Pascal, and in several other popular programming languages, defines a variable in such a way