It’s common to pass a pointer to a function. Within the function, you can manipulate the data the pointer references without having to return that data from the function. This aspect of a pointer is what makes C a powerful — and scary — programming language. But what about when you need to manipulate the pointer’s address in the function?
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It took me a while to figure out what was wrong with this month’s Exercise file. It became an obsession! Of course, I was working with a more complex version — the original code. In that code, the information is written several times to the file, and it becomes very obvious that something is wrong. But when the data is written only once, it’s tough to know whether a problem exists.
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Logic can be frustrating, especially for non-Vulcans. The computer is kind of a Vulcan, so logic comes naturally to the machine. Programming languages are packed with logical expressions. A programmer’s duty is to convert human thoughts into the raw, powerful logic the computer understands — and end up with the desired result.
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This month’s Exercise was originally how to create a structure pointer, fill it with data, and write that data to a file. It’s a procedure fraught with traps and peril. What’s even more challenging is when you’re presented with this type of code and it doesn’t work, but it’s your job to fix it.
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In last week’s Lesson, I showed a program that translates a string of hex values into ASCII text. This code was to sate the nerd in me so that when another nerd writes 48 65 6c 6c 6f 2c 20 66 65 6c 6c 6f 77 20 6e 65 72 64 21, I can respond accordingly. But to respond in hex, a second program is required, one that translates ASCII text into a string of hex values.
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Do you speak hex? As a programmer, do you look at 0xF and see 1111 in binary? Do you see 15 decimal? What about the ASCII code? Do you know the letter for code 0x41? Are you that good?
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Pulling in all the stack items mentioned in last week’s Lesson, I present to you a C program that emulates stack storage. I’m certain this presentation will be one of the highlights of your programming career.
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To simulate stack storage in a C program, you need to emulate the four basic parts of a stack:
Further, you need to implement controls that prevent a stack overflow or underflow. And you can get real fancy, but those four items are the basics.
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This month’s Exercise is to create an array of six players, assign each a random score (1 to 100), then display the player’s scores by rank. The first problem you most likely encountered was how to keep the player’s number and score together.
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Whether you simulate a stack in your C code or just ignore the concept altogether, your program constantly uses the processor’s stack. Specifically, if the code contains a function, it uses this stack not only to call and return from the function, but to pass and return arguments as well.
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