Unit categorization

Unit categorization of units provided in the Free Pascal Runtime Library is based on different criteria into several groups.

Criteria used below include different programming models (procedural, Turbo Pascal/Borland Pascal style OOP, Delphi style OOP), whether ansistrings (or more generally, reference counted types) are used or not (ansistrings are by default on with -Mdelphi/$MODE DELPHI or $H+), whether the units are cross-platform or platform specific units (with information about their availability/useability for different targets). Furthermore, basic information about type of functionality to be found in individual units should hopefully help especially new users to understand better where to search for particular routines. Finally, availability of individual units in other Pascal compilers (at least whether they are available with TP/BP, Delphi or whether they are FPC specific) are mentioned.

Procedural programming, short strings, cross-platform

System

Basic type definition, execution control, parameter processing, string handling, type conversions, mathematic operations, memory management, basic routines for console and disk I/O, constants and variables describing the particular platform and/or current environment (available in TP/BP and Delphi)

Strings

Operations with PChar strings (available in TP/BP)

Matrix

Vector and matrix routines (FPC specific)

UComplex

Operations with complex numbers (FPC specific)

GetOpts

Routines for more advanced access to program parameters

Keyboard

Low-level access to keyboard (FPC specific)

Mouse

Mouse support (FPC specific)

Video

Routines for low-level access to screen (FPC specific)

Printer

Very basic access to printer (available in TP/BP)

Sockets

Basic support for TCP/IP socket communication (FPC specific)

CMem

Replacement memory manager based on C run-time library to allow easier integration with some code written in C (FPC specific)

CTypes

Definition of C language types for easier integration with routines written in C (FPC specific)

InitC

Some functions required for linking of some libraries written in C

MacPas

Special unit supporting constructs formerly available in some Pascal compilers for Mac OS platform (ThinkPascal, Metrowerks etc.); available for all platforms with FPC to support -Mmacpas/$MODE MACPAS (FPC specific)

HeapTrc

Debugging support unit for tracing of incorrect memory allocation (more or less FPC specific, at least not available with TP/BP and probably Delphi either)

LineInfo

Debugging support unit to allow displaying of location (line) in source files in case of an error based on debug information linked to executable file (FPC specific)

Crt

More advanced console (keyboard and screen) routines (TP/BP compatibility unit plus some FPC specific functions)

Dos

More advanced disk I/O, execution flow (including running of other programs), date and time handling and access to environment variables, plus some compatibility routines only available/making sense for DOS platform (TP/BP compatibility unit plus some FPC specific functions; some of the functions were provided in WinDos unit in older Delphi versions)

Graph

Simple graphics support (TP/BP compatibility unit)

Procedural programming, ansistrings, cross-platform

SysUtils

More advanced disk I/O, execution control (including exception handling and running of other programs), access to environment variables, string routines (support of ansistrings and widestrings), conversion routines (strings, numbers, date/time), internationalization support (Delphi compatibility plus some FPC specific functions)

StrUtils

Various more advanced string routines (Delphi compatibility)

DateUtils

Date/time handling routines (Delphi compatibility)

ConvUtils

Conversion between different units of measurement (Delphi compatibility)

SysConst

Resource texts for SysUtils (Delphi compatibility?)

RTLConst

Resource texts for other RTL libraries (especially unit Classes)

DynLibs

On-demand (run time) loading of dynamic libraries

Math

More complex mathematic and statistic routines; no ansistrings really used here directly, although it loads unit SysUtils and thus installs its exception handler (Delphi compatibility with FPC specific additions)

FreeBIDI

Helper routines for bidirectional text output (FPC specific)

Utf8BIDI

Helper routines for conversion of UTF-8 encoded text supporting bidirectional output (FPC specific)

ObjPas

Basic support for -Mobjfpc and -Mdelphi including some type redefinitions and resource string support; unit used automatically for those modes, no need to add it manually (FPC specific, although the provided routines are compatible to routines available System unit with Delphi)

TP/BP style OOP, shortstrings, cross-platform

Objects

Base of the object hierarchy, disk I/O and memory operations for OOP programs - streams, resources, lists and collections (TP/BP compatibility)

FV (Free Vision) units

Complete framework for writing TP/BP-style OOP programs with text-mode windowing user interface (TP/BP compatibility - more or less compatible to Turbo Vision)

Delphi style OOP, ansistrings, cross-platform

Classes

Base of the class hierarchy, disk I/O, execution control and memory operations for OOP programs - streams, resources, lists, collections, threads, components, actions, interfaces, data modules etc. (Delphi compatibility)

VarUtils

Variant support routines (Delphi compatibility?)

FCL units

Non-visual classes for OOP programming (partly similar to Delphi VCL, but only non-visual parts are provided here; visual/GUI classes are provided with Lazarus)

Procedural programming, shortstrings

Ansistrings may be used/supported in some cases too, platform-specific.

This group is fairly extensive, only information about availability for individual platforms is given here. See the description of individual units for more information. In general, these units are FPC specific except for the Windows, WinCrt and WinSock units available with Delphi, and unit LibC available with Kylix.

Various units available for more than one platform

Ports

Support of port access construct provided with TP/BP on x86 platforms

CPU and MMX

Support of some low-level CPU-specific functions on x86 platforms

UnixType, BaseUnix, Unix, UnixUtil, SysCall, IPC

Unix platforms (Linux, *BSD including Mac OS X, Solaris, NetwLibC, plus possibly BeOS and QNX again in the future)

GPM

Unix platforms that support this library (Linux). It is less broadly supported than previous units.

x86

Unix platforms running on x86

Windows, WinMouse, WinEvent, WinSysUt, WinCrt (plus package WinUnits provided outside of RTL in "Packages")

MS Windows platforms (Win32, Win64, WinCE)

WinSock

MS Windows, OS/2 and Netware

Linux specific units

Linux

As the names implies, contains routines and symbols specific to Linux.

Libc

is Linux/x86 only, see libc_unit for more information

GO32v2 specific units

Go32, Emu387, DpmiExcp, DxeType, DxeLoad

Classic Mac OS specific units

MacOS, MacUtils

MorphOS specific units

Exec, Timer, DosLib, Utility, Hardware, InputEvent, Graphics, Layers, Intuition, Clipboard, ASL, AHI and Get9

Netware specific units

Netware, NWCalls, NWNit, NWPre, NWProt, NWServ, NWSNUt

OS/2 specific units

OS2Def

Definition of common types and constants

DosCalls

So-called "Control Program functions" - execution control (including running of other programs, threading, exceptions and error management, critical sections and semaphores), memory management, system and environment information (including environment variables, program and system parameters and national language support), disk I/O, date/time handling, inter-process communication (pipes), low-level system functions (IOCTL and communication with device drivers)

KbdCalls

Low-level access to keyboard (primarily for non-PM applications)

MouCalls

Low-level mouse support (primarily for non-PM applications)

VioCalls

Low-level video (screen) functions (non-PM)

MonCalls

Support for character device monitors (non-PM applications)

PMWin

Primary interface for GUI windowing functions provided by Presentation Manager (PM) environment

PMGpi

Support for graphical operations (PM)

PMStdDlg

Standard dialogs plus drag and drop support (PM)

PMBitmap

Bitmap picture operations (PM)

PMBidi

Support for bidirection text output (PM)

PMHelp

Interface unit for help feature (PM)

PMSpl

Access to printer spooler (PM)

PMShl

Operations with desktop including access to system ini files (PM)

PMWP

Operations with WorkPlace Shell classes (PM)

PMWSock

Support for OS/2 socket library with interface modelled after Winsock 1.1

PMDev

Support for different output devices and their capabilities (PM)

(plus package OS2Units provided outside of RTL in "Packages")

(Free)BSD specific units

Some of these may apply to other BSDs too.

Console

general "syscons" header.

sysctl

general sysctl header. Note that many other unices support sysctl, but the MIB names will probably be different on the detail level. (darwin also supports this one)