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CHAIN

Syntax

CHAIN [MERGE] <filename>[,[<line number exp>][,ALL][,DELETE<range>]]

Versions: Disk

Purpose

To call a program and pass variables to it from the current program.

Remarks

The CHAIN statement loads and runs another BASIC program, optionally passing variables to it.

Parameters:

  • MERGE - Merges the new program with the current one instead of replacing it
  • filename - Name of the program to chain to. If no extension is provided, .BAS is assumed
  • line number exp - Optional starting line number in the chained program
  • ALL - Pass all variables to the chained program (requires COMMON statement)
  • DELETE range - Delete specified lines before chaining (e.g., DELETE 1000-2000)

Variable Passing:

Variables are only passed to the chained program if they are declared in a COMMON statement. Without ALL, only COMMON variables are passed. With ALL, all variables are passed.

Memory:

The current program is removed from memory unless MERGE is specified. Open files remain open across the chain operation.

Example

10 REM Program 1 - PROG1.BAS
20 COMMON A, B$, C()
30 A = 100
40 B$ = "Hello from PROG1"
50 DIM C(10)
60 C(1) = 42
70 CHAIN "PROG2.BAS", 100

100 REM Program 2 - PROG2.BAS
110 COMMON A, B$, C()
120 PRINT "Value of A:"; A
130 PRINT "Value of B$:"; B$
140 PRINT "Value of C(1):"; C(1)

Output when running PROG1.BAS: 

Value of A: 100
Value of B$: Hello from PROG1
Value of C(1): 42

See Also

  • CLEAR - To set all numeric variables to zero and all string variables to null; and, optionally, to set the end of memory and the amount of stack space
  • COMMON - To pass variables to a CHAINed program
  • CONT - To continue program execution after a Control-C has been typed, or a STOP or END statement has been executed
  • END - To terminate program execution, close all files and return to command level
  • NEW - To delete the program currently in memory and clear all variables
  • RUN - Executes the current program or loads and runs a program from disk
  • STOP - To terminate program execution and return to command level (does not close files)
  • SYSTEM - Exits MBASIC and returns to the operating system