 Description | This month's program will allow you to print characters in giant format on the screen, enlarged from 4 to 8 times compared to the original size, thus obtaining, in a few moments, full-screen writing clearly visible even from a considerable distance.
The listing consists of a Basic part which, as usual, acts as a loader for the actual routine written in machine language and which remains resident in memory even after having deleted the Basic part. This routine can be incorporated into any program of your own creation to get large-print titles or screenshots.
To do this you have two possibilities: the first, simpler but less efficient, is to add the listing at the end of your program (after changing the line numbers), copying it or, better still, using the published "APPEND" program on no. 9, which allows you not to have to rewrite the entire listing. The second instead consists in saving and, therefore, reloading only the routine in machine language, activating it with the instruction SYS 16000.
To do this, enter Monitor and type:
S"name",1,3E00,3FFF
and press Return: in this way you will save time and memory, but you will have one more file to load. Giant characters are selected by prefixing a control character to the string to be printed:
CHR$(0) normal size
CHR$(1) magnified 4 times in width and height
CHR$(2) magnified 4x in width and 8x in height
CHR$(3) magnified 8x in width and 4x in height
CHR$(4) magnified 8x in width and height
For example, to obtain the writing GEIE magnified 8 times, you will have to use the instruction:
PRINT CHR$(4) "GEIE"
It should be noted that it is possible to use different formats in the same print line, simply by prefixing the relative control characters, and it will also be possible to obtain reverse printing. The Basic part of the listing is very simple: the data line codes are already listed in hexadecimal form, which allows you to occupy less space and make modification easier.
At line 100 the memory top is lowered to prevent the routine from being erased by variables or data.
At 110 the classic FOR-NEXT loop opens, in which the variable I represents, in addition to the loop counter, the address where the relative value will be POKEd.
At 120 the next value in the DATA lines is read, converted to decimal and stored in the corresponding location.
Line 130 closes the FOR-NEXT iterative loop.
At 140 the checksum is checked, ie the checksum of all the values of the DATA lines, to verify their accuracy; in the event of an error, the program stops to allow searching for it.
On line 150 the routine is activated with the instruction SYS 16000, which executes the instructions starting at location $3E00.
The program control codes are then displayed. The STOP instruction, on line 210, can be replaced by a NEW, when you are certain that everything is in order (remember, first, to save the program you just typed!). |
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