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Any program, whether written for business or pleasure, is the better lor good presentation and, there are often times when it would be useful to be able to vary the size of the lettering on the computer screen; to make bold headlines. etc.
Here are three short programs which will enable you to print messages on the screen in letters two. four, or eight times the normal size. Another one makes the letters appear on their sides, so that you can print a message reading from top to
The routines, inevitably, are written in machine code but I have incorporated each one in a Basic program which will place it in Ihe computer's RAM, at any address you choose. Once entered, you can save the machine code by itself, using Save name, B, < start address >, < code length> for use in your own programs.
Type in the program listings and run them. If you have made a mistake in the code, the computer should spot this and allow you to correct it. Each program gives particulars of Call addresses, number of bytes involved etc.
The routines are a little longer that they might be. as I have made them not only print the characters on Ihe screen, but also set the correct print position for the next character However, the extra finger jabs are worth it lor the ease of operation they give! I have suggested addresses for the code: if you use them, each routine will follow directly after the previous one. so Ihat you can save Ihe whole lot in one block of 310 bytes, for later use. Remember to do, Memory 36863 (one less than the point at which you want the first block to start) before running the first program, so as to make a safe area to store the code.
To use one of the routines, you must do a Call from Basic, which includes the number of the character you want printed, in the form, Call < routine address > ,< character >. This will pass the character to the program for printing (known as. "passing parameters'. in the trade). The example shows how you can deal with a message within a string, in a Basic program Program Notes Double-Sized letters
This routine uses the first four User-Graphic characters as locations to hold the big character, so if you have your own User-Graphics, you'll have to make four more spaces, by doing, Symbol After < existing number > -4, before you start - or else, you will lose your characters.
4 x Letters & 8 x Letters
Neither of these uses any special workspace, so the User-Graphics are unaffected.
This routine uses the first two graphic positions to deal with the new letters. So. if you haven't already provided extra space, for Program 1, you will have to do, Symbol After < existing number > - 2, to provide the workspace.
By altering just two Bytes in the machine code, you can make the letters face in different directions, so that a message will read from top to bottom, or from bottom to top. The two Bytes are circled in the printed program: here is what they do:
Finally, you will see that in each of the programs, three Bytes are underlined. If you change these, to make them. CD 18 BB, the program will print to screen any character you enter from the keyboard. In effect, you get a kind of Jumbo typewriter for each letter, you have to do a separate CALL, since the parameters are going to be passed from the keyboard
You just enter. Call < address > by itself, without any additional number.
If anybody who is interested in copies of the assembler listings. I'd be glad to let them have them. They should send an SAE to. J Durst. Coltscombe Barn. Swerford