| .CHAIN Statement Details. |
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| CHAIN Statement Details |
|
| Syntax |
| CHAIN filespec |
| |
| The filespec is a string expression that identifies the program to |
| which control is passed. The filespec may include a path |
| specification. |
| ž Programs running within the QuickBASIC environment assume |
| a .BAS extension (if no extension is given) and cannot chain |
| to executable files (files with a .COM or .EXE extension). |
| ž Programs running outside the QuickBASIC environment assume |
| an .EXE extension and cannot chain to QuickBASIC source files |
| (files with a .BAS extension). |
| |
| You can pass variables between programs using the COMMON statement |
| to set up a blank COMMON block. See the entry for COMMON. |
| |
| If you are compiling a program outside the QuickBASIC environment, |
| note that the BCOM45.LIB library does not support COMMON. There |
| are two ways to use COMMON with chained programs outside the |
| environment. |
| ž Use the default (BRUN45.EXE) by compiling the programs using the |
| option in the Make EXE dialog box called EXE Requiring BRUN45.EXE. |
| ž Use BRUN45.LIB by compiling from the command line without the /O |
| option. |
| |
| The behavior of CHAIN and RUN is almost identical. The principal |
| differences are that RUN closes all open files and does not support |
| COMMON data blocks. |
| |
| Note: When programs use BRUN45.LIB, files are left open during |
| chaining unless they are explicitly closed with a CLOSE |
| statement. |
| |
| Difference from BASICA |
| |
| BASICA assumes the extension .BAS. QuickBASIC assumes an extension |
| of either .BAS or .EXE, depending on whether the program is run within |
| the environment or compiled and run outside the environment. If you |
| omit the file extension, CHAIN works the same in both QuickBASIC |
| and BASICA. |
| |
| BASIC does not support the ALL, MERGE, or DELETE options available in |
| BASICA, nor does it allow you to specify a line number. |
| |
| Without the line-number option, execution always starts at the |
| beginning of the chained-to program. Thus, a chained-to program that |
| chains back to a carelessly written chaining program can cause an |
| endless loop. |
