$SystemID is a short string that identifies the type of computer system on which Mathematica is being run.

$TimeZone gives the current time zone to assume for dates and times.

The general principle that Mathematica follows in evaluating expressions is to go on applying transformation rules until the expressions no longer change. This means, for ...

Solving linear first-order ODEs is straightforward and only requires the use of a suitable integrating factor. In sharp contrast, there are a large number of methods ...

Systems of ODEs are important in various fields of science, such as the study of electricity and population biology. Like single ODEs, systems of ODEs can classified as ...

The following is a linear first-order ODE because both y[x] and y^ ′[x] occur in it with power 1 and y^′[x] is the highest derivative. Note that the solution contains the ...

The function Flatten allows you to explicitly flatten out all sublists. FlattenAt lets you specify at what positions you want sublists flattened. Sequence objects ...

When you define a complicated function, you will often want to let some of the arguments of the function be "optional". If you do not give those arguments explicitly, you ...

Many large-scale applications of linear algebra involve matrices that have many elements, but comparatively few that are nonzero. You can represent such sparse matrices ...

Expressions corresponding to cells. Here is a notebook containing a text cell and a Mathematica input cell. Here are the expressions corresponding to these cells.