Enhanced BASIC, errata. 18th Dec. 2001 By Lee Davison.

Sometimes, when cold starting, the interpreter would either crash totally or give spurious error messages such as "Out of memory error." or "Syntax error." instead of reporting the ammount of free memory. This was more likely the less memory BASIC had available.

The end of array memory pointer hadn't been set at this point and could cause the print string subroutine, which prints the string created from the bytes free value, to think that no memory was available. Also, as the pointers weren't all set yet, the garbage collection routine could then either fail, causing the "Out of memory" error, or crash causing other errors or even a hung machine.

The fix for this is easy, it just entails moving the "NEW" and "CLEAR" call to before you try to print anything.

Just after LAB_2E05 was ..

JSR LAB_CRLF ; print CR/LF LDA Ememl ; get end of mem low byte SEC ; set carry for subtract SBC Smeml ; subtract start of mem low byte TAX ; copy to X LDA Ememh ; get end of mem high byte SBC Smemh ; subtract start of mem high byte JSR LAB_295E ; print XA as unsigned integer (bytes free) LDA #LAB_SMSG ; point to sign-on message (high addr) JSR LAB_18C3 ; print null terminated string from memory JSR LAB_1463 ; do "NEW" and "CLEAR" LDA #LAB_1274 ; warm start vector high byte STA Wrmjpl ; save warm start vector low byte STY Wrmjph ; save warm start vector high byte JMP (Wrmjpl) ; go do warm start

.. and this now becomes ..

JSR LAB_CRLF ; print CR/LF JSR LAB_1463 ; do "NEW" and "CLEAR" LDA Ememl ; get end of mem low byte SEC ; set carry for subtract SBC Smeml ; subtract start of mem low byte TAX ; copy to X LDA Ememh ; get end of mem high byte SBC Smemh ; subtract start of mem high byte JSR LAB_295E ; print XA as unsigned integer (bytes free) LDA #LAB_SMSG ; point to sign-on message (high addr) JSR LAB_18C3 ; print null terminated string from memory LDA #LAB_1274 ; warm start vector high byte STA Wrmjpl ; save warm start vector low byte STY Wrmjph ; save warm start vector high byte JMP (Wrmjpl) ; go do warm start

.. This ensures that the "bytes free." message always prints correctly and is done in version 1.01.

Last page update: 14th July, 2003.

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