Not Implemented Features¶

This document lists features found in other BASIC dialects that are not in MBASIC 5.21.

Graphics (Not in MBASIC 5.21)¶

These graphics commands are from GW-BASIC and QuickBASIC, not MBASIC 5.21:

SCREEN - Set graphics mode
PSET - Plot pixel
LINE - Draw line (GW-BASIC graphics version - not the LINE INPUT statement which IS implemented)
CIRCLE - Draw circle
PAINT - Fill area
DRAW - Draw using string commands
GET/PUT - Graphics block operations (not the file I/O GET/PUT which ARE implemented)
PALETTE - Color palette
VIEW - Set viewport
WINDOW - Set coordinate system

Why not implemented: MBASIC 5.21 predates graphics BASIC. These features were added in GW-BASIC and later versions.

Alternative: Use modern graphics libraries outside BASIC if needed.

Sound (Not in MBASIC 5.21)¶

Sound commands from later BASICs:

SOUND - Generate tone
PLAY - Play music string
BEEP - System beep

Why not implemented: MBASIC 5.21 had no sound support.

Alternative: Use PRINT CHR$(7) for system beep (bell character).

Advanced Control Flow (Not in MBASIC 5.21)¶

These are from QuickBASIC and later:

SELECT CASE - Multi-way branch
DO...LOOP - Flexible looping
EXIT FOR/WHILE - Break out of loop
CONTINUE - Skip to next iteration

Why not implemented: MBASIC 5.21 only has FOR...NEXT, WHILE...WEND, GOTO, GOSUB.

Alternative: - Use IF...THEN for multi-way: 10 IF X=1 THEN GOTO 100: IF X=2 THEN GOTO 200 - Use WHILE...WEND instead of DO...LOOP - Use GOTO to exit loops early

Procedures (Not in MBASIC 5.21)¶

QuickBASIC introduced structured programming:

SUB...END SUB - Subroutines with parameters
FUNCTION...END FUNCTION - Functions with return values
DECLARE - Forward declarations
CALL - Call subroutine by name
STATIC/SHARED - Variable scope keywords
LOCAL - Local variables

Why not implemented: MBASIC 5.21 only has GOSUB for subroutines and DEF FN for simple functions.

Alternative: - Use GOSUB for subroutines (no parameters, global variables) - Use DEF FN for single-expression functions

Advanced Data Types (Not in MBASIC 5.21)¶

Later BASICs added:

LONG - 32-bit integer
CURRENCY - Fixed-point decimal
TYPE...END TYPE - User-defined types/structures
VARIANT - Variable type
CONST - Named constants

Why not implemented: MBASIC 5.21 has only INTEGER, SINGLE, DOUBLE, STRING.

Alternative: Use what's available or define constants as variables.

File Handling Extensions¶

Advanced file features from later versions:

BINARY mode - Binary file access beyond GET/PUT
APPEND mode - Simplified append
ACCESS READ/WRITE - File locking
SHARED - File sharing modes
FILEATTR - File attributes
FREEFILE - Find available file number
DIR$ - Directory listing
CHDIR/MKDIR/RMDIR - Directory operations

Why not implemented: MBASIC 5.21 has basic sequential and random file I/O only.

Available in MBASIC 5.21: - Sequential files (INPUT/OUTPUT mode) - Random access files - OPEN, CLOSE, GET, PUT, FIELD - KILL (delete file) - NAME (rename file)

Event Handling (Not in MBASIC 5.21)¶

Event-driven features from GW-BASIC:

ON TIMER - Timer events
ON KEY - Keyboard events
ON COM/PEN/STRIG - Hardware events
TIMER - System timer

Why not implemented: MBASIC 5.21 is not event-driven.

Alternative: Poll for conditions in a loop.

Memory Management¶

Advanced memory features:

CLEAR (extended) - Set stack/string space
FRE(-1) - Largest free block
FRE(-2) - Stack space
SETMEM - Set memory limits
ERDEV$ - Device error

Available in MBASIC 5.21: - Basic CLEAR (clear variables) - FRE(0) (free memory) - PEEK/POKE (limited in this implementation)

Hardware Access¶

CP/M-specific or hardware features:

INP/OUT/WAIT - I/O ports (not portable)
USR - Machine language calls (not portable)
BLOAD/BSAVE - Binary load/save
DEF SEG - Segment register
CALL ABSOLUTE - Call machine code

Why not implemented: Not portable to modern systems, hardware-specific.

Note: PEEK/POKE are emulated with virtual memory in this implementation.

String Enhancements¶

Later BASIC features:

LCASE $/UCASE$ - Change case (use your own routine)
**LTRIM $/RTRIM$ /TRIM $** - Trim whitespace (use LEFT$ /RIGHT $/MID$ )
REPLACE$ - String replacement
SPLIT - Split string
JOIN - Join strings

Available in MBASIC 5.21: - LEFT $, RIGHT$ , MID$ - Extract substrings - INSTR - Find substring - LEN - String length - STR$/VAL - Number conversion

What IS Available¶

MBASIC 5.21 includes:

✓ All standard statements (FOR, WHILE, IF, GOTO, GOSUB, etc.) ✓ File I/O (sequential and random) ✓ Arrays (multi-dimensional) ✓ String manipulation (LEFT $, RIGHT$ , MID$, INSTR, etc.) ✓ Math functions (SIN, COS, TAN, LOG, EXP, SQR, etc.) ✓ Error handling (ON ERROR GOTO, RESUME, ERR, ERL) ✓ User-defined functions (DEF FN) ✓ Data statements (DATA, READ, RESTORE) ✓ All four data types (INTEGER, SINGLE, DOUBLE, STRING)