A program is a text, viz. the formulation of some algorithm, expressed in a programming language. This text obeys the syntax of the programming language, and according to that syntax consists of a nested collection of constructs. Among these constructs, three general classes can be distinguished: <#1431#>algorithms<#1431#>, <#1432#>objects<#1432#> and <#1433#>types<#1433#>, which have the distinction that they can be denoted by names. The program text consists of such <#1434#>entities<#1434#>, glued together by control structures, data structures and further composition mechanisms such as expressions and functional application.