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USR

Implementation Note

⚠️ Not Implemented: This feature calls machine language (assembly) routines and is not implemented in this Python-based interpreter.

Behavior: Always returns 0

Why: Cannot execute machine code from a Python interpreter. USR was designed to call hand-written assembly language subroutines for performance-critical operations or hardware access.

Alternative: Use DEF FN to define custom functions in BASIC, or implement performance-critical operations using BASIC's built-in functions.

Historical Reference: The documentation below is preserved from the original MBASIC 5.21 manual for historical reference.

Description

Calls the user's assembly language subroutine with the argument X. is allowed in the Extended and Disk versions only. is in the range 0 to 9 and corresponds to the digit supplied with the DEF USR statement for that routine. If is omitted, USR0 is assumed.

Example

40 B = T*SIN (Y)
 50 C = USR (B/2)
 60 D = USR(B/3)

See Also

  • FRE - Arguments to FRE are dummy arguments
  • HELP SET - Display help for a specific setting
  • INKEY$ - Returns either a one-character string containing a character read from the terminal or a null string if no character is pending at the terminal
  • INP - Returns the byte read from port I
  • LIMITS - Display resource usage and interpreter limits
  • NULL - To set the number of nulls to be printed at the end of each line
  • PEEK - Returns the byte (decimal integer in the range 0 to 255) read from memory location I
  • RANDOMIZE - To reseed the random number generator
  • REM - To allow explanatory remarks to be inserted in a program
  • SET (setting) - Configure interpreter settings at runtime
  • SHOW SETTINGS - Display current interpreter settings
  • TRON/TROFF - To trace the execution of program statements
  • VARPTR - Returns the memory address of a variable
  • WIDTH - To set the printed line width in number of characters for the terminal or line printer