Comparison of Pascal and Delphi

Devised by Niklaus Wirth in the late 1960s and early 1970s, Pascal is a programming language. Originally produced by Borland Software Corporation, Embarcadero Delphi is composed of an IDE, set of standard libraries, and a Pascal-based language commonly called either Object Pascal, Delphi Pascal, or simply 'Delphi' (Embarcadero's current documentation refers to it as 'the Delphi language (Object Pascal)' ). Since first released, it has become the most popular commercial Pascal implementation.

While developing Pascal, Wirth employed a bootstrapping procedure in which each newer version of the Pascal compiler was written and compiled with its predecessor. Thus, the 'P2' compiler was written in the dialect compilable by 'P1', 'P3' in turn was written in 'P2' and so on, all the way till 'P5'. The 'P5' compiler implemented Pascal in its final state as defined by Wirth, and subsequently became standardised as 'ISO 7185 Pascal'.

The Borland dialect, like the popular UCSD Pascal before it, took the 'P4' version of the language as its basis, rather than Wirth's final revision. After much evolution independent of Standard Pascal, the Borland variant became the basis for Delphi. This page goes over the differences between Delphi and Standard Pascal. It does not go into Delphi-specific extensions to the language, which are numerous and still increasing.

Exclusive features
Following features are mutually exclusive. The Standard Pascal implementation is not accepted by Delphi and vice versa, the Delphi code is not acceptable in Standard Pascal.

Modulo with negative dividend
Standard Pascal has a Euclidean-like definition of the  operator whereas Delphi uses a truncated definition.

Nested comments
Standard Pascal requires that the comment delimiters  and the bigramm , as well as   and   are synonymous to each other. In Delphi, however, a block comment started by  must be closed with a. The bigramm  will only close any comment that started with. This scheme allows for nested comments at the expense of compiler complexity.

Procedural data types
The way procedures and functions can be passed as parameters differs: Delphi requires explicit procedural types to be declared where Standard Pascal does not.

Conversion of newline characters
Various computer systems show a wide variety how to indicate a newline. This affects the internal representation of  files which are composed of a series of “lines”. In order to relieve the programmer from any associated headaches, Standard Pascal mandates that reading an “end-of-line character” returns a single space character. To distinguish such an “end-of-line” space character from a space character that is actually genuine payload of the line,  becomes.

Delphi does not show this behavior. Reading a newline will return whatever character sequence represents a newline on the current host system, for example two  values   (carriage return) plus   (line feed).

Additional or missing features
Following features are present or missing in either language.

Global
Standard Pascal permits a  to any   defined in scope. In Delphi a  must be within the current routine, i. e. may not leave the -frame.

Buffer variables
Delphi does not support buffer variables and associated standard routines  and.

Discriminated variant record allocation
In Standard Pascal allocating memory for a variant  may indicate a specific variant. This allows implementations to allocate the least amount of really necessary memory. Delphi does not support this.

Temporary files
In Delphi any file must be backed by a file in the file system. That means any  needs to be associated with a file name with Delphi's   procedure. In contrast, Standard Pascal is usable without file names. The following will produce a run-time error with Delphi.

Packing
Delphi does not implement the standard procedures  and. Regardless, transferring data between packed and unpacked data types is an easy feat, although the implementation might not be as efficient as a compiler vendor supplied implementation would be.

Missing default width
Delphi does not associate the data type  with a default width if specified as  /  parameters. Delphi demonstrates the behavior as usual for character-strings.

Overloading
Delphi permits overloading routines. In Standard Pascal identifiers must be unique in every block.

Default parameter values
Delphi permits default parameters.

Standard width
In Pascal, if the destination file is a  file, the parameters to  /  have an implemention-defined default total width. In Delphi, for  values this is simply. That means always the least amount of space is occupied. Other compilers have shown default widths of, for example,  allowing for a fine tabular look at no cost of extra code.