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FreeBASIC string functions are inherited from QuickBASIC + a few modern additions.

String functions

DIM s AS STRING
s = "hello world"

LEN(s)                 ' 11
UCASE(s)                ' "HELLO WORLD"
LCASE(s)                ' "hello world"

LEFT(s, 5)              ' "hello"
RIGHT(s, 5)             ' "world"
MID(s, 7, 5)            ' "world" (start, length — 1-indexed!)
MID(s, 7)               ' "world" (to end)

LTRIM(s)                ' strip leading whitespace
RTRIM(s)                ' strip trailing whitespace
TRIM(s)                 ' both

INSTR(s, "world")        ' 7 (1-indexed position)
INSTR(8, s, "l")         ' 10 (search starting from 8)
INSTR(s, "xyz")          ' 0 (not found)

Note: positions are 1-indexed in BASIC string functions — historic legacy.

Concatenation

DIM full AS STRING
full = "Hello, " & "World!"
' or:
full = "Hello, " + "World!"   ' also works for strings

Use & for clarity — + is ambiguous (could mean numeric add).

Character / number conversion

ASC("A")                ' 65 (ASCII code)
CHR(65)                 ' "A"
CHR(13)                  ' carriage return

STR(42)                  ' "42" (no leading space in FreeBASIC)
VAL("42 hello")          ' 42 (parse leading number)
VAL("abc")              ' 0 (no number found)

Old QBASIC's STR$ put a leading space before positive numbers; FreeBASIC's STR does not — STR(42) is exactly "42", and negatives keep their - sign. (The $-suffixed names like STR$/CHR$ are QB-dialect only and will not compile here.)

PRINT formatting

Comma — column zones (every 14 chars):

PRINT "a", "b", "c"
' a             b             c

Semicolon — no spacing (concat):

PRINT "a";"b";"c"
' abc

Mixing:

DIM person AS STRING = "Ada"
DIM age AS INTEGER = 36
PRINT person; " is "; age; " years old"
' Ada is 36 years old

Note: FreeBASIC's PRINT does NOT add spaces around numbers joined with ; (old QBASIC did) — put the spaces in your strings, as " is " and " years old" do above.

PRINT USING — formatted output

PRINT USING "###.##"; 3.14159     ' "  3.14"
PRINT USING "$$#,##0.00"; 1234.5   ' "$1,234.50"
PRINT USING "\     \"; "hi"        ' left-pad to backslash gap

The template chars:

• # — digit position
• 0 — required digit (zero pad)
• . — decimal point
• , — thousands separator
• $ — currency
• \...\ — string field of N chars
• +/- — sign

Closest BASIC has to printf.

sprintf-style with FORMAT

FreeBASIC has a FORMAT function (put #include "string.bi" at the top of your file):

#include "string.bi"

DIM s AS STRING
s = FORMAT(3.14159, "0.00")     ' "3.14"
s = FORMAT(99.5, "0.0\%")        ' "99.5%"

For more complex formatting, build with & and helper functions.

Multi-line strings

No triple-quote literals. Use CHR(10) for newlines:

DIM block AS STRING
block = "line 1" & CHR(10) & "line 2" & CHR(10) & "line 3"
PRINT block