One of my first programming obsessions was online communications. I wrote several modem programs for the TRS-80 (in Z80 Assembly) and then moved to the IBM PC/MS-DOS where I coded communications programs in both Assembly and C. I learned a few things.
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The final (and merciful) update to my Grid of Random Stars program involves two major changes. First, because I call the update_grid() function only once, it can be incorporated into the main() function, no program. Second, I remove pointer notation.
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The program may output what I want, but the code isn’t done yet. Continuing from last week’s Lesson, I’d like the program to output a single grid showing a summary of all the rectangles found. This update requires more changes to the existing code.
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The two problems I recognized in the code from last week’s Lesson were that scan_column() and find_right() don’t need to be separate functions. Also, the code fails to find all the rectangles in the grid, which is bad. Time to fix the code!
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I was so excited with last week’s code that I didn’t bother to confirm that it worked properly. No, I was eager to see graphic output of the found rectangles.
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The next update to my pattern-finding program is to hunt down and find a clutch of asterisks in the grid that form a rectangle. Figure 1 illustrates what I’m after.
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To count all possible rectangles in a random grid requires a lot of scanning. My first thought was that the process would involve recursion. I wasn’t 100 percent certain, but I wanted to prep the code for such a possibility.
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Ever since I was a little boy and coded my first nested loop, I’ve enjoyed messing with grids in C. I’ve done monthly calendars in grids, rotated grids, manipulated grids mathematically — all sorts of fun girddy stuff. But I’m not done yet.
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Array notation involves the array’s name followed by a set of square brackets. Within these brackets is a reference to the array element’s number. It’s important to remember that the first element is zero. But the subscript need not always be a constant integer.
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I’m always mindful of the beginner when I write code for this blog. Even with my own code, I often go to pains to write things “the long way” just because I’m in the habit. Not every coder is so thoughtful. The reason is that C tends toward obfuscation. We must revel in this capability.
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