what is "b:" ??? (input/output)

This is a discussion on what is "b:" ??? (input/output) within the C Programming forums, part of the General Programming Boards category; i'm following a textbook to learn C, and the following example was used to show how to Program-Controlled Input and ...

  1. #1
    Registered User TheSupremeAbode's Avatar
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    what is "b:" ??? (input/output)

    i'm following a textbook to learn C, and the following example was used to show how to Program-Controlled Input and Output files...

    Code:
    #include <stdio.h>
    #define KMS_PER_MILE 1.609
     
    int
    main(void)
     
    {
     
    double miles, kms;
     
    /* set pointers */
    FILE *inp, *outp;
     
    /* open input/output files */
    inp = fopen("b:input_file.txt", "r"); 
    outp = fopen("b:output_file.txt", "w");
     
    /* get and echo info */
    fscanf(inp, "%1f", miles);
    fprintf(outp, "The distance in miles is %.2f.\n", miles);
     
    /* convert distance to kms */
    kms = KMS_PER_MILE * miles;
     
    /* display distance in kms */
    fprintf(outp, "That equals %.2f kilometers.\n", kms);
     
    /* close files */
    fclose(inp);
    fclose(outp);
     
    return(0);
     
    }
    the trouble is, I run it and it doesn't work.

    I have tried searching for "b:" as it was used here:

    Code:
    /* open input/output files */
    inp = fopen("b:input_file.txt", "r"); 
    outp = fopen("b:output_file.txt", "w");
    in google to find out what it does, but I have found nothing.


    What the heck?

  2. #2
    Gawking at stupidity
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    "b:" is a drive letter, used in the DOS/Windows world. Just consider it part of the path. Try substituting it with "c:\\input_file.txt" (note: you have to double the backslash) or, if you're in a *NIX environment, "/home/tsa/input_file.txt".
    If you understand what you're doing, you're not learning anything.

  3. #3
    msh
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    Or just leave it as "input_file.txt", if the file is in the current working directory.
    Disclaimer: This post shows my ignorance at the time of its making. I claim ownership of but not responsibility for all errors in it. Reference at your own peril.

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    Registered User TheSupremeAbode's Avatar
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    Quote Originally Posted by itsme86 View Post
    "b:" is a drive letter, used in the DOS/Windows world. Just consider it part of the path. Try substituting it with "c:\\input_file.txt" (note: you have to double the backslash) or, if you're in a *NIX environment, "/home/tsa/input_file.txt".
    right, okay.

    I was trying to run the above-mentioned program, as a batch file, from a command prompt.

  5. #5
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    Wait... what? You put the C code in a file, and gave that file a .bat extension, and tried to execute it?

  6. #6
    ATH0 quzah's Avatar
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    Quote Originally Posted by TheSupremeAbode View Post
    I have tried searching for "b:" as it was used here:

    Code:
    /* open input/output files */
    inp = fopen("b:input_file.txt", "r"); 
    outp = fopen("b:output_file.txt", "w");
    in google to find out what it does, but I have found nothing.


    What the heck?
    This post makes me feel old. As stated, b: is a drive indicator. But they're using it wrong, because you have to have a separator after it. You can't just b:foo.txt, you need b:\foo.txt. I guess most people now have never had a b drive.

    Quzah.
    ... is old.
    Hope is the first step on the road to disappointment.

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    msh
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    Ah, the ye olde days, when floppies were all we had. The kids have no idea how good they have it these days!
    Disclaimer: This post shows my ignorance at the time of its making. I claim ownership of but not responsibility for all errors in it. Reference at your own peril.

  8. #8
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    The floopy disks were awesome. A set of 1.2mb and 1.4mb used to store all the games.
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    Is but a dream within a dream." - Poe

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    Registered User TheSupremeAbode's Avatar
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    lol

    I didn't save it as .bat, I compiled it from a .c source file; then tried to run the EXE via command prompt

  10. #10
    Registered User TheSupremeAbode's Avatar
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    when computers were louder than vaccum cleaners, this wee lad played Oregon Trail and learnt very fast not to name your family members after the family members who were crossing ye olde trail during game play.

    http://www.elephantjournal.com/wp-co...egon-trail.jpg

    And hunting? Call of Duty doesn't have s*it on Oregon Trail.

    http://www.nostalgiaholic.com/wp/wp-...on-hunting.gif

  11. #11
    Algorithm Dissector iMalc's Avatar
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    Yeah I remember playing lots of Oregon trail. I stupidly tried to ford rivers 2 metres (6 foot) deep. Then I'd go hunting in winter and catch nothing. Good times...
    My homepage
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  12. #12
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    Quote Originally Posted by quzah View Post
    This post makes me feel old. As stated, b: is a drive indicator. But they're using it wrong, because you have to have a separator after it. You can't just b:foo.txt, you need b:\foo.txt. I guess most people now have never had a b drive.

    Quzah.
    ... is old.
    b:file.txt is valid - it looks for file.txt in the current directory on the B: drive. DOS maintains a current working directory for each drive, and using the letter plus a colon with no slash accesses that current directory so you don't have to retype it in full.

    C:\foo > cd b:\bar REM changes current active dir on B: even though you're in C
    C:\foo > dir b: REM this will display b:\bar since it's the active directory on b:

    Now whether or not that's what's desired in this case is an entirely different matter. Looks dangerous here since you have no idea what you're accessing.

  13. #13
    'Allo, 'Allo, Allo
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    Quote Originally Posted by KCfromNC View Post
    b:file.txt is valid - it looks for file.txt in the current directory on the B: drive. DOS maintains a current working directory for each drive, and using the letter plus a colon with no slash accesses that current directory so you don't have to retype it in full.

    C:\foo > cd b:\bar REM changes current active dir on B: even though you're in C
    C:\foo > dir b: REM this will display b:\bar since it's the active directory on b:
    As you demonstrated, that's now a cmd convention which is faked by environment vars not an OS convention. On NTFS file systems, b:test.txt would be the test.txt alternate data stream of the extensionless file b. But I think we're all agreed it's a copy error, and not some obsequious path convention.
    Last edited by adeyblue; 01-31-2011 at 01:39 PM. Reason: I didn't abide by normal spelling conventions

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