Below is a quick summary of the functions available in the system unit.
abs Calculate absolute value AbstractError Generate an abstract error. AcquireExceptionObject Obtain a reference to the current exception object AddExitProc Add an exit procedure to the exit procedure chain. Addr Return address of a variable Align Return aligned version of an address AllocMem Allocate and clear memory. AnsiToUtf8 Convert ansi string to UTF-8 string Append Open a file in append mode arctan Calculate inverse tangent ArrayStringToPPchar Concert an array of string to an array of null-terminated strings Assert Check validity of a given condition. Assign Assign a name to a file Assigned Check if a pointer is valid BasicEventCreate Obsolete. Don't use basiceventdestroy Obsolete. Don't use basiceventResetEvent Obsolete. Don't use basiceventSetEvent Obsolete. Don't use basiceventWaitFor Obsolete. Don't use BeginThread Start a new thread. BEtoN Convert Big Endian-ordered integer to Native-ordered integer binStr Convert integer to string with binary representation. BlockRead Read data from an untyped file into memory BlockWrite Write data from memory to an untyped file Break Exit current loop construct. chdir Change current working directory. chr Convert byte value to character value Close Close a file CompareByte Compare 2 memory buffers byte per byte CompareChar ompare 2 memory buffers character per character CompareChar0 Compare two buffers character by character till a null-character is reached. CompareDWord Compare 2 memory buffers DWord per DWord CompareWord Compare 2 memory buffers word per word Concat Append one string to another. Continue Continue with next loop cycle. cos Calculate cosine of angle Cseg Return code segment Dec Decrease value of variable DefaultAnsi2WideMove Standard implementation of Ansi to Widestring conversion routine DefaultWide2AnsiMove Standard implementation of Widestring to Ansi conversion routine Delete Delete part of a string. Dispose Free dynamically allocated memory DoneCriticalsection Clean up a critical section. Dseg Return data segment Dump_Stack Dump stack to the given text file. DynArraySetLength Set the length of a dynamic array EndThread End the current thread. EnterCriticalsection Enter a critical section EOF Check for end of file EOLn Check for end of line Erase Delete a file from disk Error 32-bit signed integer. Exclude Exlude element from a set if it is present. Exit Exit current subroutine. exp Exponentiate FilePos Get position in file FileSize Size of file FillByte Fill memory region with 8-bit pattern FillChar Fill memory region with certain character FillDWord Fill memory region with 32-bit pattern FillWord Fill memory region with 16-bit pattern FindResource Locate a resource and return a handle to it. float_raise Raise floating point exception Flush Write file buffers to disk FlushThread Flush all standard files frac Return fractional part of floating point value. Freemem Release allocated memory Freememory Alias for FreeMem FreeResource Free a loaded resource GetCurrentThreadId Return the id of the currently running thread. getdir Return the current directory GetFPCHeapStatus Return FPC heap manager status information GetHeapStatus Return the memory manager heap status. GetMem Allocate new memory on the heap GetMemory Alias for GetMem GetMemoryManager Return current memory manager GetProcessID Get the current process ID GetThreadID Get the current Thread ID. GetThreadManager Return the current thread manager GetVariantManager Return the current variant manager. GetWideStringManager Return a copy of the currently active widestring manager. get_caller_addr Return the address of the caller. get_caller_frame Return the frame pointer of the caller get_frame Return the current frame halt Stop program execution. hexStr Convert integer value to string with hexadecimal representation. hi Return high byte/word of value. High Return highest index of open array or enumerated HINSTANCE Windows compatibility type for use in resources Inc Increase value of integer variable Include Include element in set if it was not yet present. IndexByte Search for a byte in a memory range. IndexChar Search for a character in a memory range. IndexChar0 Return index of a character in null-terminated array of char. IndexDWord Search for a DWord value in a memory range. Indexword Search for a WORD value in a memory range. InitCriticalSection Initialize a critical section InitThread Initialize a thread InitThreadVars Initialize threadvars Insert Insert one string in another. int Calculate integer part of floating point value. InterlockedCompareExchange Conditional exchange InterLockedDecrement Thread-safe decrement InterLockedExchange Exchange 2 integers in a thread-safe way InterLockedExchangeAdd Thread-safe add and exchange of 2 values InterLockedIncrement Thread-safe increment IOResult Return result of last file IO operation IsMemoryManagerSet Is the memory manager set KillThread Kill a running thread LeaveCriticalsection Leave a critical section LEtoN Convert Little Endian-ordered integer to Native-ordered integer ln Calculate logarithm lo Return low byte/word of value. LoadResource Load a resource for use LockResource Lock a resource longjmp Jump to address. Low Return lowest index of open array or enumerated lowerCase Return lowercase version of a string. MemSize Return the size of a memory block. mkdir Create a new directory. Move Move data from one location in memory to another MoveChar0 Move data till first zero character New Dynamically allocate memory for variable NtoBE Convert Native-ordered integer to a Big Endian-ordered integer NtoLE Convert Native-ordered integer to a Little Endian-ordered integer Null Null variant OctStr Convert integer to a string with octal representation. odd Is a value odd or even ? Ofs Return offset of a variable. Ord Return ordinal value of an ordinal type. Paramcount Return number of command-line parameters passed to the program. ParamStr Return value of a command-line argument. pi Return the value of PI. Pos Search for substring in a string. Pred Return previous element for an ordinal type. prefetch Prefetch a memory location ptr Combine segment and offset to pointer RaiseList List of currently raised exceptions. Random Generate random number Randomize Initialize random number generator Read Read from a text file into variable ReadLn Read from a text file into variable and goto next line Real2Double Convert Turbo Pascal style real to double. ReAllocMem Re-allocate memory on the heap ReAllocMemory Alias for ReAllocMem ReleaseExceptionObject Decrease the reference count of the current exception object. Rename Rename file on disk Reset Open file for reading ResumeThread Resume a suspended thread. Rewrite Open file for writing rmdir Remove directory when empty. round Round floating point value to nearest integer number. RTLEventCreate Create a new RTL event RTLeventdestroy Destroy a RTL Event RTLeventResetEvent Reset an event RTLeventSetEvent Notify threads of the event. RTLeventsync Obsolete. Don't use RTLeventWaitFor Wait for an event. RunError Generate a run-time error. Seek Set file position SeekEOF Set file position to end of file SeekEOLn Set file position to end of line Seg Return segment Setjmp Save current execution point. SetMemoryManager Set a memory manager SetMemoryMutexManager Procedure to set the mutex manager. SetString Set length of a string and copy buffer. SetTextBuf Set size of text file internal buffer SetTextLineEnding Set the end-of-line character for the given text file. SetThreadManager Set the thread manager, optionally return the current thread manager. SetVariantManager Set the current variant manager. SetWideStringManager Set the widestring manager sin Calculate sine of angle SizeOf Return size of a variable or type. SizeofResource Return the size of a particular resource Space Return a string of spaces Sptr Return current stack pointer sqr Calculate the square of a value. sqrt Calculate the square root of a value Sseg Return stack segment register value. Str Convert a numerical value to a string. StringOfChar Return a string consisting of 1 character repeated N times. StringToPPChar Split string in list of null-terminated strings StringToWideChar Convert a string to an array of widechars. strlen Length of a null-terminated string. strpas Convert a null-terminated string to a shortstring. Succ Return next element of ordinal type. SuspendThread Suspend a running thread. Swap Swap high and low bytes/words of a variable SwapEndian Swap endianness of the argument SysAllocMem System memory manager: Allocate memory SysAssert Standard Assert failure implementation SysBackTraceStr Format an address suitable for inclusion in a backtrace SysFreemem System memory manager free routine. SysFreememSize System memory manager free routine. SysGetFPCHeapStatus Return the status of the FPC heapmanager SysGetHeapStatus System implementation of GetHeapStatus SysGetmem System memory manager memory allocator. SysInitExceptions Initialize exceptions. SysInitStdIO Initialize standard input and output. SysMemSize System memory manager: free size. SysReAllocMem System memory manager: Reallocate memory SysResetFPU Reset the floating point unit. SysTryResizeMem System memory manager: attempt to resize memory. ThreadGetPriority Return the priority of a thread. ThreadSetPriority Set the priority of a thread. ThreadSwitch Signal possibility of thread switch trunc Truncate a floating point value. Truncate Truncate the file at position UCS4StringToWideString Unassigned Unassigned variant. UnicodeToUtf8 UniqueString Make sure reference count of string is 1 UnlockResource Unlock a previously locked resource upCase Convert a string to all uppercase. UTF8Decode UTF8Encode Utf8ToAnsi Utf8ToUnicode Val Calculate numerical value of a string. VarArrayRedim Redimension a variant array VarCast WaitForThreadTerminate Wait for a thread to terminate. WideCharLenToString Convert a length-limited array of widechar to an ansistring WideCharLenToStrVar Convert a length-limited array of widechar to an ansistring WideCharToString Convert a null-terminated array of widechar to an ansistring WideCharToStrVar Convert a null-terminated array of widechar to an ansistring WideStringToUCS4String Convert a widestring to a UCS-4 encoded string. Write Write variable to a text file WriteLn Write variable to a text file and append newline