Well, we pulled a fast one on you all last month. We were testing you and noone wrote and said that we left out the second column in James Brezina’s review of MACHINE CODE TUTOR!
Actually, it was a mistake on our part. Somewhere between pasting the issue up and printing it, the paste-up column fell off revealing part of May’s article “Tape Makes a Difference” and obviously it does because this “tape” didn’t stick!
Here is the column that is missing. We suggest that you take this page and copy it and cut out the missing column and use good tape and stick it in its proper place in last month’s article. Our apologies go out to all of our readers and to Mr. Brezina for messing up his article.
The Missing Column:
line appears. From then on, you can use any key to step through the program. The action explained does not occur until you key to the next step, then the registers specified by the instruction show numbers. It is interesting to see how the Program Counter steps through the program, especially with calls and jumps. Here I encountered one of the things I find wrong with the program. As an example, a line will contain the following mnemonic: LD DE,8740. The DE pair at the bottom will show the number in that register pair and will show the HL register pair as containing 243 although that register pair has not been stepped to in the program. There is no explanation of this in the program.
After the ML program is completed, you are given the choice of RUNing it again, editing it, or returning to the menu. If you key enter, you are given the choice of loading another set of lessons or going to the assembler. Once you enter the assembler, you can no longer return to the lessons loaded in. The assembler can be entered directly from the first section without loading in any lessons. You can enter your own programs in the assembler.
You can enter a label of up to six characters or you can hit the space key and jump 7 spaces to where you can enter mnemonics and numbers. I only tried decimal numbers. There is a way to switch the display between decimal and hexadecimal. After entering a line, pressing ENTER advances you so you can enter the next line. After you have entered all the lines of your program, you key STOP and it will assemble your program and show the same screen as in the lesson examples. You can then run the program in the same way as the lesson’s examples.
There are a number of things that I don’t like about this program. In a program entered through other assemblers, you can specify addresses for jumps or offsets for relative jumps. In this one you cannot. You must label lines to be jumped to and use that label in the jump. You are limited to only 15 lines for the program. You are limited to addresses 16384 to 23295 and 32000 to 32192 for your