Comparison of Pascal and Delphi on arvau

Wikipedia / Comparison of Pascal and Delphi

Pascal is a programming language devised by Niklaus Wirth in the late 1960s and early 1970s. Originally produced by Borland Software Corporation, 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 mod operator whereas Delphi uses a truncated definition.

Nested comments

Standard Pascal requires that the comment delimiters and the bigram , 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.

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 goto

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 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. However, Delphi allows a class, object, or record to be declared as "packed", which minimizes the space they use.

Missing default write 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.

Peculiar implementation characteristics

Standard write width

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