The string handling routines in SysUtils handle both UnicodeString and AnsiString types. Within their functional areas, some routines are used for the same purpose, the differences being whether they use a particular criterion in their calculations. 

The AnsiStrings unit's functions offer the same capabilities as the SysUtils unit's routines. AnsiStrings functions provide better performance for AnsiString than SysUtils functions, because SysUtils functions convert an AnsiString to a UnicodeString. AnsiStrings functions work only with AnsiString, so there is no conversion. 

The following tables list these routines by these functional areas:

• Comparison
• Case conversion
• Modification
• Sub-string

Where appropriate, the tables also provide columns indicating whether a routine satisfies the following criteria.

• Uses case sensitivity: If locale settings are used, it determines the definition of case. If the routine does not use locale settings, analyses are based upon the ordinal values of the characters. If the routine is case-insensitive, there is a logical merging of upper and lower case characters that is determined by a predefined pattern.
• Uses locale settings: Locale settings allow you to customize your application for specific locales, in particular, for Asian language environments. Most locale settings consider lowercase characters to be less than the corresponding uppercase characters. This is in contrast to ASCII order, in which lowercase characters are greater than uppercase characters. Routines that use the system locale are typically prefaced with Ansi (that is, AnsiXXX).
• Supports the multi-byte character set (MBCS): MBCSs are used when writing code for far eastern locales. Multi-byte characters are represented by one or more character codes, so the length in bytes does not necessarily correspond to the length of the string. The routines that support MBCS parse one- and multibyte characters.

ByteType and StrByteType determine whether a particular byte is the lead byte of a multibyte character. Be careful when using multibyte characters not to truncate a string by cutting a character in half. Do not pass characters as a parameter to a function or procedure, since the size of a character cannot be predetermined. Pass, instead, a pointer to a to a character or string. For more information about MBCS, see Enabling Application Code. 

String length routines:

Note that Length and SizeOf give different results for all strings except for short strings. SizeOf equals the number of bytes in a pointer, since non-short strings are pointers. 

String comparison routines:

Case conversion routines:

String modification routines:

Sub-string routines:

String information routines (in System):