ChrB Function

Returns a String containing the character associated with the specified ANSI character code. The "B" suffix indicates this is the byte (ANSI) version of the Chr function.

Syntax

ChrB(charcode)

Parameters

• charcode: Required. Long. A numeric expression that identifies a character in the ANSI character set. Valid values are 0-255.

Returns

Returns a String containing a single byte character corresponding to the specified ANSI code.

Remarks

• ChrB is used to return ANSI characters (single-byte characters).
• The B suffix stands for "Byte", distinguishing it from the Unicode ChrW function.
• Numbers from 0 to 31 are standard, non-printable ASCII codes. For example, ChrB(10) returns a linefeed character.
• Numbers from 32 to 127 are standard printable ASCII characters.
• Numbers from 128 to 255 are extended ANSI characters (varies by code page).
• If charcode is outside the range 0-255, a runtime error occurs (Error 5: Invalid procedure call or argument).
• ChrB is particularly useful when working with byte arrays or legacy ANSI text.
• For Unicode characters, use ChrW instead of ChrB.

Typical Uses

1. Building strings with specific byte values - Construct ANSI strings byte-by-byte
2. Creating control characters - Generate line feeds, carriage returns, tabs, etc.
3. Low-level text manipulation - Work with binary data or legacy file formats
4. ANSI text generation - Create strings for systems expecting ANSI encoding
5. Byte array operations - Convert byte values to string representations
6. Legacy protocol support - Work with older communication protocols using ANSI

Basic Examples

' Example 1: Simple character conversion
Dim ch As String
ch = ChrB(65)  ' Returns "A"

' Example 2: Creating control characters
Dim newline As String
newline = ChrB(13) & ChrB(10)  ' CR+LF

' Example 3: Building a string from byte codes
Dim text As String
text = ChrB(72) & ChrB(101) & ChrB(108) & ChrB(108) & ChrB(111)  ' "Hello"

' Example 4: Display a character
MsgBox ChrB(65)  ' Displays "A"

Common Patterns

' Pattern 1: Creating line breaks
Dim CRLF As String
CRLF = ChrB(13) & ChrB(10)
text = "Line 1" & CRLF & "Line 2"

' Pattern 2: Tab-separated values
Dim TAB As String
TAB = ChrB(9)
data = "Name" & TAB & "Age" & TAB & "City"

' Pattern 3: Building ANSI strings from byte array
Dim i As Integer
Dim result As String
Dim bytes() As Byte
bytes = Array(72, 101, 108, 108, 111)
For i = LBound(bytes) To UBound(bytes)
result = result & ChrB(bytes(i))
Next i

' Pattern 4: Creating null-terminated strings
Dim nullTerm As String
nullTerm = "Hello" & ChrB(0)

' Pattern 5: Character range generation
Dim alphabet As String
Dim i As Integer
For i = 65 To 90
alphabet = alphabet & ChrB(i)
Next i  ' "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

' Pattern 6: Control character constants
Const NULL_CHAR As String = ChrB(0)
Const BELL_CHAR As String = ChrB(7)
Const BACKSPACE As String = ChrB(8)
Const TAB_CHAR As String = ChrB(9)
Const LF_CHAR As String = ChrB(10)
Const CR_CHAR As String = ChrB(13)

' Pattern 7: Escape special characters
Dim quote As String
quote = ChrB(34)  ' Double quote character
result = quote & "Hello" & quote  ' "Hello"

' Pattern 8: Binary data to string conversion
Function BytesToString(bytes() As Byte) As String
Dim i As Long
Dim result As String
For i = LBound(bytes) To UBound(bytes)
result = result & ChrB(bytes(i))
Next i
BytesToString = result
End Function

' Pattern 9: Creating delimited strings
Dim PIPE As String
PIPE = ChrB(124)  ' "|" character
data = "Field1" & PIPE & "Field2" & PIPE & "Field3"

' Pattern 10: ASCII art or special symbols
Dim box As String
box = ChrB(218) & String(10, ChrB(196)) & ChrB(191)  ' Top of box

Advanced Examples

' Example 1: Complete ANSI string builder
Function BuildANSIString(byteCodes() As Integer) As String
Dim i As Integer
Dim result As String

For i = LBound(byteCodes) To UBound(byteCodes)
If byteCodes(i) >= 0 And byteCodes(i) <= 255 Then
result = result & ChrB(byteCodes(i))
Else
Err.Raise 5, , "Invalid byte code: " & byteCodes(i)
End If
Next i

BuildANSIString = result
End Function

' Example 2: Legacy file format writer
Sub WriteLegacyFormat(filename As String, data As String)
Dim f As Integer
Dim i As Integer
Dim checksum As Byte

f = FreeFile
Open filename For Binary As #f

' Write header with STX (Start of Text)
Put #f, , ChrB(2)

' Write data
Put #f, , data

' Calculate and write checksum
checksum = 0
For i = 1 To Len(data)
checksum = checksum Xor Asc(Mid(data, i, 1))
Next i
Put #f, , ChrB(checksum)

' Write ETX (End of Text)
Put #f, , ChrB(3)

Close #f
End Sub

' Example 3: Character encoding converter
Function ConvertToANSI(text As String) As String
Dim i As Integer
Dim result As String
Dim charCode As Integer

For i = 1 To Len(text)
charCode = Asc(Mid(text, i, 1))
If charCode <= 255 Then
result = result & ChrB(charCode)
Else
result = result & ChrB(63)  ' "?" for unmappable chars
End If
Next i

ConvertToANSI = result
End Function

' Example 4: Binary protocol message builder
Function CreateProtocolMessage(msgType As Byte, payload As String) As String
Dim msg As String
Dim length As Integer

length = Len(payload)

' SOH (Start of Header)
msg = ChrB(1)

' Message type
msg = msg & ChrB(msgType)

' Length (2 bytes, little-endian)
msg = msg & ChrB(length Mod 256)
msg = msg & ChrB(length \ 256)

' STX (Start of Text)
msg = msg & ChrB(2)

' Payload
msg = msg & payload

' ETX (End of Text)
msg = msg & ChrB(3)

CreateProtocolMessage = msg
End Function

Error Handling

Function SafeChrB(charcode As Long) As String
On Error GoTo ErrorHandler

If charcode < 0 Or charcode > 255 Then
Err.Raise 5, , "Character code must be between 0 and 255"
End If

SafeChrB = ChrB(charcode)
Exit Function

ErrorHandler:
SafeChrB = ""
MsgBox "Error converting character code " & charcode & ": " & Err.Description
End Function

Performance Notes

• ChrB is very fast for single-byte character operations.
• When building large strings, consider using a byte array and converting once at the end.
• String concatenation in a loop can be slow; use StringBuilder pattern if available.
• ChrB(0) through ChrB(31) are control characters and may not display visibly.

Best Practices

1. Use named constants for common control characters instead of magic numbers
2. Validate character codes are in the range 0-255 before calling ChrB
3. Use ChrB for ANSI/byte operations, ChrW for Unicode operations
4. Document when using non-printable characters (codes 0-31)
5. Consider code page issues when working with extended ANSI (128-255)
6. Use vbCrLf constant instead of ChrB(13) & ChrB(10) when possible

Comparison with Related Functions

Platform Notes

• ChrB behavior is consistent across Windows platforms.
• Extended ANSI characters (128-255) may vary by system code page.
• In VB6, strings are internally Unicode but ChrB returns ANSI byte values.
• ChrB is primarily for backward compatibility with older code.

Common Character Codes

• 0: Null character
• 7: Bell/beep
• 8: Backspace
• 9: Tab
• 10: Line feed (LF)
• 13: Carriage return (CR)
• 32: Space
• 34: Double quote
• 39: Single quote/apostrophe
• 65-90: Uppercase A-Z
• 97-122: Lowercase a-z
• 48-57: Digits 0-9

Limitations

• Only supports ANSI character codes (0-255).
• Cannot represent Unicode characters beyond the ANSI range.
• Code page dependent for values 128-255.
• Runtime error if charcode is outside valid range.