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File Format Compatibility

Line Endings (Newlines)

MBASIC saves all program files using LF line endings (Line Feed, \n, Unix-style).

What This Means

  • Loading files: MBASIC automatically handles files with any line ending style:
  • LF (\n, Unix/Linux/Mac)
  • CRLF (\r\n, Windows/CP/M)

  • CR (\r, Classic Mac)

  • Saving files: MBASIC always saves with LF line endings (\n)

Why Unix Line Endings?

  • Cross-platform compatibility: Modern text editors on all platforms (Windows, Mac, Linux) handle LF correctly
  • Modern Windows support: Windows Notepad (since Windows 10 1809), VS Code, Notepad++, and other editors all support LF
  • Web UI consistency: Browser-based editing works the same on all operating systems
  • Git-friendly: Standard for version control systems

Using Files with CP/M Emulators

If you want to transfer saved BASIC files to a CP/M emulator (such as tnylpo), you may need to convert the line endings from LF (\n) to CRLF (\r\n), as CP/M systems expect CRLF line endings.

Converting to CP/M Format

On Linux/Mac: 

# Convert LF to CRLF
unix2dos yourfile.bas

# Or using sed
sed -i 's/$/\r/' yourfile.bas

# Or using Python
python3 -c "import sys; data=open('yourfile.bas','rb').read(); open('yourfile.bas','wb').write(data.replace(b'\n',b'\r\n'))"

On Windows (PowerShell): 

# Using PowerShell to convert
(Get-Content yourfile.bas) | Set-Content yourfile.bas

Using a utility script:

MBASIC includes a utility script for CP/M conversion: 

# Convert a file to CP/M format (CRLF line endings)
python3 utils/convert_to_cpm.py yourfile.bas

Assembly Source Files (.mac)

Note: Assembly source files (.mac) in the docs/history/original_mbasic_src/ directory retain their original CRLF line endings because they are intended for use with the CP/M M80 assembler, which requires CRLF format.

Character Encoding

MBASIC uses UTF-8 encoding for all files. However, when loading files:

  • Parity bits are cleared: High bit (bit 7) is stripped from characters
  • Control characters are filtered: Most control characters are removed (except CR, LF, TAB)
  • CP/M EOF markers removed: Ctrl+Z (\x1a) end-of-file markers are stripped

This ensures compatibility with files created on vintage systems that may have used 7-bit ASCII with parity or included CP/M-specific markers.

File Extensions

MBASIC recognizes these file extensions:

  • .bas - Standard BASIC program files (recommended)
  • .BAS - Uppercase variant (also supported)
  • .txt - Plain text files containing BASIC code

All are treated identically when loading.

Line Number Format

BASIC program lines must start with a line number (1-65535) followed by at least one space:

10 PRINT "HELLO"
20 FOR I=1 TO 10
30 PRINT I
40 NEXT I

Lines without line numbers are ignored when loading files.

Compatibility Notes

From Real MBASIC 5.21

Files created with the original Microsoft MBASIC 5.21 (from CP/M systems) can be loaded directly. MBASIC will: - Convert CRLF line endings to LF automatically - Strip any CP/M EOF markers (^Z) - Clear parity bits if present

To Real MBASIC 5.21

To transfer files TO a real MBASIC 5.21 system or CP/M emulator: 1. Save the file in MBASIC 2. Convert line endings to CRLF (see "Converting to CP/M Format" above) 3. Optionally add CP/M EOF marker: echo -e '\x1a' >> yourfile.bas

Other BASIC Dialects

MBASIC implements the Microsoft MBASIC 5.21 dialect. Files from other BASIC interpreters (GW-BASIC, QBASIC, etc.) may load but could have syntax differences. See the language documentation for specifics.