plz help me make my assigment more bulletproof

when i compile the program, the avg is displaying a garbage value (-1.#J) because i did 0/0 which is an error. So my question is how can i fix this. Also, when i want to input a string character how can i make the program to read the whole string character. For example if i type in (ghjk) it should be not valid. But instead its reading (g). Also, my program is reading a negative value how can i stop that it should say "inproper input".

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Firstly, don't use fflush(stdin).
cpwiki.sf.net/fflush
http://faq.cprogramming.com/cgi-bin/...&id=1043284351

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while(time!='q'&& time!='Q');

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That's the same as

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while(tolower(time) != 'q');

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if you have <ctype.h> included. And time() is a standard function, so calling a variable that is not the best idea. It works, however, at least until you try to call time(). :)

tolower()/toupper() would make your switch statement a great deal smaller. You should look into it. http://www.cprogramming.com/fod/tolower.html

Also, instead of having all of those variables (a, b, c, d, ...), consider looking into arrays. http://www.cprogramming.com/tutorial/c/lesson8.html

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#define    A      "smarties"
#define    A_P    4.55
#define    B      "Flour  "
#define    B_P    1.5

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printf() can add spaces for you. &#37;10s pads the string with spaces to be at least 10 characters long, and %-10s will left align it, printing the spaces on the right. (%10s will give you " one", %-10s will give you "one ".) For example:

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printf("%-10s something\n%-10s else\n", "one", "two";

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prints

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one        something
two        else

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Now for your real questions. :)

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when i compile the program, the avg is displaying a garbage value (-1.#J) because i did 0/0 which is an error. So my question is how can i fix this.

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Whenever you do division, check to see if you're dividing by zero. For example:

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if(y == 0) puts("Division by zero");
else printf("= %f\n", x / y);

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Also, when i want to input a string character how can i make the program to read the whole string character. For example if i type in (ghjk) it should be not valid. But instead its reading (g).

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http://faq.cprogramming.com/cgi-bin/...&id=1043284385

In essence, you need to declare variables as arrays:

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char data[10];  /* a string with a maximum length of 9 (add one for the NULL) */

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Then read them with, say, fgets():

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fgets(data, 10, stdin);

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Then, if you use fgets(), remove the newline from the end of the string:

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char *p;
p = strchr(data, "\n");
if(p) *p = 0;

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Then compare the string with strcmp,

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if(strcmp(data, "yes") == 0) {
    puts("You entered \"yes\".");
}

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or, if you like, examine the first character with data[0].

> p = strchr(data, "\n");
dwks, means

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p = strchr(data, '\n');

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...
printf("\n\n\tA\tSmarties\t%3.2f\t%8.2f\t$%8.2f",A_P,a,sub1=a*A_P);
...
printf("\n\n\n\ttotal pounds =\t%8.2f\tSUBTOTAL\t$%8.2f",
          i=a+b+c+d+e+f+g+h,run=sub1+sub2+sub3+sub4+sub5+sub6+sub7+sub8);

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Excuse me while I go away and puke.

This printf is unreadable enough without the assignment inside it. Do at least this:

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...
sub1=a*A_P;
printf("\n\n\tA\tSmarties\t%3.2f\t%8.2f\t$%8.2f",A_P,a,sub1);
...
run=sub1+sub2+sub3+sub4+sub5+sub6+sub7+sub8;
i=a+b+c+d+e+f+g+h;
printf("\n\n\n\ttotal pounds =\t%8.2f\tSUBTOTAL\t$%8.2f", i, run);

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Using single letter variable names is probably not the greatest idea.

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Mats

What a mess. Adding some spaces between your operators would also make the code much easier to read. And you really need to simplify some of your statements because they are very difficult to follow. It's ugly not to mention highly error prone.

Also are you working with floats or doubles? Floats would work just fine.