help about fread and fwrite
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hello guys, Im trying to understand how fread and fwrite works. My teacher said that these functions can store/output binaries and texts in files. I know how to do it with string. Im confused with floats and integers.
I tried to make a program for it but Im getting errors. I can't run my program. Can anyone tell me whats wrong? Here is my code.
I tried to make a program for it but Im getting errors. I can't run my program. Can anyone tell me whats wrong? Here is my code.
int save(float d)
{
FILE *fp;
char fn[50];
printf("What is the filename? ");
flushall();
gets(fn);
if((fp = fopen(fn, "wb")) == NULL)
{
printf("Cannot save file");
return 0;
}
fwrite(d, sizeof(float), 1, fp);
printf("\nFile saved");
fclose(fp);
return 0;
}
int load()
{
FILE *fp;
float b;
char fn[50];
printf("What is the filename? ");
flushall();
gets(fn);
fp = fopen(fn, "rb");
fread(b, sizeof(float), 1, fp);
fclose(fp);
printf("%.2f", b);
return 0;
}
Is it so hard job to correct obvious errors: you get compiler messages on wrong function arguments: fread and fwrite want POINTERS to target/source data areas (&d - not d, &b - not b))!
Use code tag properly:
[code=c]
source
[/code]
Never use dangerous gets function: it does not check target buffer size. Use fgets instead of gets:
With gets you program crashed if the file name length is greater than 49.
Don't forget to append carriage return:
Avoid using of non-standard function flushall().
Use code tag properly:
[code=c]
source
[/code]
Never use dangerous gets function: it does not check target buffer size. Use fgets instead of gets:
c Syntax (Toggle Plain Text)
Don't forget to append carriage return:
c Syntax (Toggle Plain Text)
Avoid using of non-standard function flushall().
Last edited by ArkM : Nov 23rd, 2008 at 9:45 am.
I'm more of a newb but feeling cocky as always:
Don't AVOID compiler specific functions, but be sure to find a cross-compiler way to do it as well, as in: find it, use it a couple of time, memorize it.
However, I think it's a definite plus if you also know compiler specific tweaks.
Don't AVOID compiler specific functions, but be sure to find a cross-compiler way to do it as well, as in: find it, use it a couple of time, memorize it.
However, I think it's a definite plus if you also know compiler specific tweaks.
Last edited by Clockowl : Nov 23rd, 2008 at 1:26 pm.
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Originally Posted by Clockowl 
I'm more of a newb but feeling cocky as always:
Don't AVOID compiler specific functions, but be sure to find a cross-compiler way to do it as well, as in: find it, use it a couple of time, memorize it.
However, I think it's a definite plus if you also know compiler specific tweaks.
Well, repeat your admonitions when you will port 500000 LOC with compiler-specific calls in the new environment
... Nah I just meant to say that if you're sure that you'll only use it on your system, why not use those compiler specific functions? I think it's overkill to make basically everything you create cross platform, but if you're coding for your job then you should I guess... I'm a hobby coder. 
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Originally Posted by ArkM
Is it so hard job to correct obvious errors: you get compiler messages on wrong function arguments: fread and fwrite want POINTERS to target/source data areas (&d - not d, &b - not b))!
Use code tag properly:
[code=c]
source
[/code]
Never use dangerous gets function: it does not check target buffer size. Use fgets instead of gets:
With gets you program crashed if the file name length is greater than 49.c Syntax (Toggle Plain Text)
Don't forget to append carriage return:
c Syntax (Toggle Plain Text)
Avoid using of non-standard function flushall().
Last edited by Whilliam : Nov 24th, 2008 at 6:19 am.
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