A.13.5 Between Versions 4 and 5
44 completely new built-in objects have been added, some of whose names may conflict with names already being used.
Precision and Accuracy now return exact measures of uncertainty in numbers, not just estimates of integer numbers of digits.
Precision now returns the symbol MachinePrecision for machine numbers, rather than the numerical value $MachinePrecision.
N[expr, MachinePrecision] is now used for numerical evaluation with machine numbers; N[expr, $MachinePrecision] generates arbitrary-precision numbers.
ConstrainedMin and ConstrainedMax have been superseded by Minimize, Maximize, NMinimize and NMaximize.
SingularValues has been superseded by SingularValueList and SingularValueDecomposition. SingularValueDecomposition uses a different and more complete definition.
FindRoot[f, x, , ] is now used to specify a starting vector value for x, rather than a pair of values. The same is true for FindMinimum.
DSolveConstants has been superseded by the more general option GeneratedParameters.
TensorRank has been replaced by ArrayDepth.
$TopDirectory has been superseded by $InstallationDirectory and $BaseDirectory.
The default setting for the MathLink LinkProtocol option when connecting different computer systems is now "TCPIP" rather than "TCP".