Cookie Thief
well its just for the start of my morse code program, I want the user to select a bunch of options for exampleOriginally Posted by pkt-zer0
Morse code conversion program
write text to be converted: 1
select a text file to be converted: 2
and so on and so on, and any other option would simply yield a the same prompt if you know what I mean.
Disciple of Zerthimon
That's what the code I put there does. Just add a few more cases, one for every menu option you need, and add a function that does that, and launch it there. I was unclear again, I'm afraid, so here's a part of a small, simplified database-management proggy.
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Cookie Thief
Thanks. I'm not trying to get you to do my assessment for me, I'm just trying to understand a few functions that I think I can't understand. Here is my one if I can remember correctlyThat's what the code I put there does. Just add a few more cases, one for every menu option you need, and add a function that does that, and launch it there. I was unclear again, I'm afraid, so here's a part of a small, simplified database-management proggy.
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Links are hidden from guests. Please register to be able to view these links. hmm, I'll have to look a bit more at my notes, I might show you my binary conversion program just to get a few critisms from you
Disciple of Zerthimon
Just a few corrections.
int main(int argc, char* argv[])
The latter is an array of strings, used to pass arguments to the program from the command line. You won't be using it that much, however.
getchar()
As I've pointed out, getchar is a function, returning the last input character, so you'll have to store its return value in a variable. Correct usage would be c = getchar();
if(getchar == 1)
Very, very wrong.
Cookie Thief
Hmm. Don't want to interrupt, but how about this...
//removed the code
Last edited by MegaVolt; 22nd-December-2005 at 19:13.
Cookie Thief
Hmm okies, thanks Pkt and megavolt, I'll note these.
Cookie Thief
Sorry I couldn't wrote it earlier because of sudden OS crash,
but although my code works...somehow...almost like it should
I think you'll do better if you stick
with what pkt-zer0 wrote...well yeah it's the best way.
Cookie Thief
I got it working now. the program has a basic selection thingy that selects 4 options (based on 1,2,3,4 being pressed) I included a thing that said
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Links are hidden from guests. Please register to be able to view these links. After I finish the rest of the program, I'm going to try and fix that so it will merely prompt it again, now I need to understand how to get arrays and pointers workingI have a basic idea, but theory and practice are two different things
'ajqa'QItty
That they are, and learning is a concept that comes from combing both. In other words, try it and see what happens. Also, (not reading back yet) if you're using C/C++ your printf will give you.... Alot of problems....
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Links are hidden from guests. Please register to be able to view these links. Format, being a const char array, is easily fixed with "SOMETHING HERE" and you use "%[flag]" for where you want your variables, then place them in appearance order. Where variabes are, you seperate them with a comma.
FLAGS(the "percent codes"):
i = int
c = char
s = string
wc = wide char
ws = wide string
I forget what the others are, but you'd probably only ever need float other than that.
ADDITION:
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Links are hidden from guests. Please register to be able to view these links. Same as above, only you need to make things into longs or shorts, there is a hard way to do this, and there is an easy way to do this. The hard way is probably what you're guessing as reading this. Easy way is to put the L infront of a constant array.
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Links are hidden from guests. Please register to be able to view these links. Now there are ways of getting input. (In wide, i don't know what non wide equivalent of _getws is so i'll use wide examples, i stress on wide anyway, because international characters are slower but less biased!)
scanf (wide: wscanf) is just like printf (wprintf) only that for arrays you must include widths... now, i forget how to do that so bear with me... lol the alternative route is the fallowing...
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Links are hidden from guests. Please register to be able to view these links. variable, being an array, it's just like getline only you don't have to specify size and stuff. And i'm not about to go into file streams, go to msdn if you want that. lol
As for arrays! Well, won't take you long to get used to them... Pointers... on the other hand are annoying... I don't like pointers. Sometimes pointers can be unpredictable if you want to use them to store data. [u]never use them to store large amounts of data.[/b] Sometimes when i use pointers for dynamic allocation, i find the program crashing... Don't know if that's my fault, or if it's the fact that pointers without referances are unpredictable.
And a trick:
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Last edited by kohlrak; 24th-December-2005 at 19:56.
Cookie Thief
hmm, I see, I'll have to get figure something out for that when I get to it, my next problem is reading arrays, at the moment I have 2 arrays, the alphabet, and the morsecode all laid out in order, what I need to do is to get it so that for every letter typed, 4 characters of morsecode is printed. so I'll probably spend tomorrow figuring that out, I have a decent idea of how to go about it, but I've had this day off because I really can't be arsed with it today
'ajqa'QItty
i made an edit while you posted, just read up on it.
As for your problem... Might help to use string...
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Links are hidden from guests. Please register to be able to view these links. Then do all the cases... And for each letter, you make the morse code letter appear in the string with something like Download Links:
Links are hidden from guests. Please register to be able to view these links. Might be an easier way to go at that, but that's how i'd take that one on. lol Now getting the string into a char array, ask PKT or someone for that. I always had trouble with that. Just take all the values and put them in a dynamically made array like below....
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Links are hidden from guests. Please register to be able to view these links. Note strings dont' directly convert to char array or chars. So.... Like i said, ask for that one, but don't ask me. lol
Cookie Thief
hmm. You see I think they want me to use a strcpy fucntion, and they don't want it done that I put 1 value for 1 value if you know what I mean, I think they want me to be able to take a value from a array and point it to another value from another value, I'll try and post it later
Disciple of Zerthimon
Kohlrak, you're giving terribly wrong advice in some places, so let me elaborate.
First, the declaration of printf is incorrect, because it uses a variable length argument list. Doesn't matter much, though.
printf(a); // Prints a 1 on the screen (or should)
As you yourself have written, the first argument is a pointer to a character constant. 'a' having the value of 1, you'd be printing out garbage data.
A short explanation of how data is handled in computers.
You've got a little amount of space in the CPU itself for variable storage, so you won't be able to process larger amounts of data simply by whacking it in the registers. That's why you have... RAM! That little rascal simply does one thing: you tell it where the piece of data you want is located, and it tells you what it is, in return.
So, usually data you'll be using will be referred to by an 'offset' or 'memory address'.
In C, this goes the following way: when you declare a variable, (int a), the compiler allocates memory for it, and remembers its memory address. Afterwards, you'll be able to refer to this data in memory simply by the variable name. This is clear so far, at least I hope so.
In short: you'll be working with memory addresses, that are automatically derefered, or in case of bigger data structures, you'll have to handle that as well.
Arrays in C are simply pointers that have a fixed value, and point to a contiguous area of memory. (The term 'pointer' is equivalent to a variable holding a memory address, in most cases)
printf("%c", a); // It's an int, but it's set as c so it's like using a cast, it'll be displayed as a char.
Casting is an entirely different matter. This works this way simple due to how variable length argument lists are handled in C. They supplement NO information on the type of the argument, only its value. So, whatever might stand there, is interpreted as a character, as the format string ("%c") indicates. In C++, there's typeof, and operator overloading, getting around this problem.
File streams: You've already gone into them, whether you noticed it, or not.
The thing is, that functions like scanf, printf, and the like use the so called 'standard input/output', AKA stdin and stdout. Guess what, these are handled as files, too. You have functions like fscanf and fprintf, that do the same as their simple cousins, only that they let you specify the file you want to use, and not defaulting to stdin/stdout.
Sometimes pointers can be unpredictable if you want to use them to store data. never use them to store large amounts of data. Sometimes when i use pointers for dynamic allocation, i find the program crashing... Don't know if that's my fault, or if it's the fact that pointers without referances are unpredictable.
There is no random factor in programming, get used to it. Programs don't crash without a reason. What I'm getting to is that for basically any kind of program, you'll need to use pointers. For the simple reason that they let you handle data in a fast and efficient way, and also allow for neat data constructs like linked lists or binary trees. If you're going to have a database, you'll be needing them. Also, pointers are the only way to manage large amounts of data.
b="333"; // too small, compilation error.
Compiles correctly.
Also, I believe that Theo's currently learning C, so including operator overloading would be pretty freaky.
Morse coding could be most easily implemented with a binary tree, by the way, but an associative array could work as well.
The former is a dynamic data structure that should be familiar to you (I believe Java already has that premade), the latter is simply the concept of having a 256 element array, each containing a morse string, and ASCII codes would designate the proper string in the array. So that morse['c'] would point to the string that contains the morse code of 'c'.
Last edited by pkt-zer0; 24th-December-2005 at 20:49.
'ajqa'QItty
Well yea.. But things crash when i use pointers as variables. It won't auto allocate... But wait... Are you saying i could read byte 0 in the ram by declaring a pointer that equals 1? (please do elaborate on this cause if so this would solve a few problems i've had in the past.)Kohlrak, you're giving terribly wrong advice in some places, so let me elaborate.
First, the declaration of printf is incorrect, because it uses a variable length argument list. Doesn't matter much, though.
printf(a); // Prints a 1 on the screen (or should)
As you yourself have written, the first argument is a pointer to a character constant. 'a' having the value of 1, you'd be printing out garbage data.
A short explanation of how data is handled in computers.
You've got a little amount of space in the CPU itself for variable storage, so you won't be able to process larger amounts of data simply by whacking it in the registers. That's why you have... RAM! That little rascal simply does one thing: you tell it where the piece of data you want is located, and it tells you what it is, in return.
So, usually data you'll be using will be referred to by an 'offset' or 'memory address'.
In C, this goes the following way: when you declare a variable, (int a), the compiler allocates memory for it, and remembers its memory address. Afterwards, you'll be able to refer to this data in memory simply by the variable name. This is clear so far, at least I hope so.
In short: you'll be working with memory addresses, that are automatically derefered, or in case of bigger data structures, you'll have to handle that as well.
Keyword: Like, but thanks for pointing that out.Arrays in C are simply pointers that have a fixed value, and point to a contiguous area of memory. (The term 'pointer' is equivalent to a variable holding a memory address, in most cases)
printf("%c", a); // It's an int, but it's set as c so it's like using a cast, it'll be displayed as a char.
Casting is an entirely different matter. This works this way simple due to how variable length argument lists are handled in C. They supplement NO information on the type of the argument, only its value. So, whatever might stand there, is interpreted as a character, as the format string ("%c") indicates. In C++, there's typeof, and operator overloading, getting around this problem.
But do people really ever reffer to them as file streams? Even though they are... When you use them you save them to the screen's cache (or somthing along those lines) while STDIN saves it to your RAM as an unnamed file but each value has it's own location in ram. (Like the sectors on the hard drive.)File streams: You've already gone into them, whether you noticed it, or not.
The thing is, that functions like scanf, printf, and the like use the so called 'standard input/output', AKA stdin and stdout. Guess what, these are handled as files, too. You have functions like fscanf and fprintf, that do the same as their simple cousins, only that they let you specify the file you want to use, and not defaulting to stdin/stdout.
I mean as stand alone variables to store large amounts of data. And there is a random factor, the human. which consists of everything run before and after the program.Sometimes pointers can be unpredictable if you want to use them to store data. never use them to store large amounts of data. Sometimes when i use pointers for dynamic allocation, i find the program crashing... Don't know if that's my fault, or if it's the fact that pointers without referances are unpredictable.
There is no random factor in programming, get used to it. Programs don't crash without a reason. What I'm getting to is that for basically any kind of program, you'll need to use pointers. For the simple reason that they let you handle data in a fast and efficient way, and also allow for neat data constructs like linked lists or binary trees. If you're going to have a database, you'll be needing them. Also, pointers are the only way to manage large amounts of data.
Maybe in c... But not C++. Try that one again. lol
b="333"; // too small, compilation error.
Compiles correctly.
Wait, that's theo? Daaaang. lol He keeps changing his name can't tell it's him. Woulda helped to know that before then i woulda revised some of this ahead of time.Also, I believe that Theo's currently learning C, so including operator overloading would be pretty freaky.
Meh... Big problem is though, that you can't add more than one char to 1 char. Therefore, you'd have to directly output to the stream you want to use, but for quick revising, you could print it to variables first rather than editing alot of printfs you could edit just one... But... If they want direct stream printing, better do that. lolMorse coding could be most easily implemented with a binary tree, by the way, but an associative array could work as well.
The former is a dynamic data structure that should be familiar to you (I believe Java already has that premade), the latter is simply the concept of having a 256 element array, each containing a morse string, and ASCII codes would designate the proper string in the array. So that morse['c'] would point to the string that contains the morse code of 'c'.
On a lighter (yet more complicated note), how exactly does a processor get the values of a string to compare? Like in C++ you can compare variable "33A" and "33A" and it'd return true while any unequal would return false. Does it just put them all together and read their binary as one big number? If so, then why can't we make an int or somthing big enough to handle that value? (would make quite the amusement project, don't you think? lol) Then each possible string would have it's own value. Then instead of something like "0x6A, 0x66,0x44" it'd be 0x6A6644 which (luckily, hex is close enough to binary to combine the numbers to make somthing like that, the equivalent in decimal would be much uglier to figure out. But it would be "106, 102, 68" verses "6972996". Which, if you sit and do the math, no other string could possibly have that value. lol)
I autta come up with my own compression aligoritham thinger. lol i have been meaning to do it, and when i do it won't be much of compression. lol And unless you're doing a 1+ gig file or somthing, the compression wouldn't be worth it (accept with text files of course). Probably some one came up with my idea but i'd give me somthing to do. lol
Disciple of Zerthimon
You couldn't read byte zero in the RAM under Windows that easily, since Windows manages memory. But by dereferencing a zero pointer, you're technically trying to read the program's code you're running, thereby causing an access violation. That's why your programs crash, most likely.
And why would pointers auto-allocate?
Yeah, people do. BTW, I believe direct access to any kind of memory is long gone since DOS, so they're absolutely no different from a file, except that they do not get saved to hard disk, but somewhere else. Due to this naming being a bit confusing, under C++ you have IOStream classes, which can just as convieniently be used for reading files or stdin.
Anyhow, if you want to see how much of files they are, you can indeed reassign stdin and stdout, thereby making a program read 'keyboard input' from a file, and outputting it into another file.
Yes, but that doesn't change what the program itself does.
What kind of compiler are you using?
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Links are hidden from guests. Please register to be able to view these links. First part reads a sample file, associating the characters with morse codes. Then it displays those codes appropriate for each keypress. No error checking, memory cleanup, and that sort of stuff, but you get the idea. And yes, kohlrak, it uses... pointers!
It depends on how it's implemented in the standard library. Most common would be to go character-by-character on the two strings, calculate the difference of the characters ASCII codes, and if it's not zero, return it, otherwise continue comparing.
The reason you can't put a string in a single variable to handle it is that C uses zero terminated strings, unlike Pascal, where the first byte of a string was its length. You can have arbitarily long strings in C (as in: possibly a hundred gazillion letters long), but obviously you can't have arbitarily large variables (int, long int, and the like have an implementation defined size)
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