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Written By A. J. Hynd

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Visual Recall

A. J. Hynd, Hayling Island, Hampshire

This program allows the contents of memory to be displayed and examined. I have used this on my BBC Model A to recover programs, which have become corrupted when saved or loaded, by examining the line numbers and line lengths in the stored Basic program. Errors can be calculated and then corrected by Poking new data into the appropriate addresses.

The start addresses can be entered in either decimal or hexadecimal form, but all displayed values are in hex. Lines 20 and 30 set page mode and print format, and line 130 resets these on Escape.

The input procedure first checks to see if the entry is a hex number otherwise it checks for valid decimal inputs.

I found the EVAL function very useful for converting the string input to a hex number. The Shift key is used to give further pages of display, and the Escape key to exit.

The program has to be entered so as not to overwrite the memory contents you wish to examine. First Load the program to be examined but do not Run, then enter:

PAGE = TOP+&100

Then Load this program which can be RUN without affecting your first program; to reset enter:

PAGE = &E00

which is where Basic programs are normally stored for conventional purposes.