How do we cast an argv[]

This is a discussion on How do we cast an argv[] within the C Programming forums, part of the General Programming Boards category; Hi everyone, I would like to know how do we cast an argv[] if I want to check whether it ...

  1. #1
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    How do we cast an argv[]

    Hi everyone,

    I would like to know how do we cast an argv[] if I want to check
    whether it is equal to some integer number or decimal in C ?

    another question what is the difference between unsigned char and char ?

  2. #2
    Registered User sean345's Avatar
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    To turn a string like argv[0] or argv[x] into a integer you can use atoi(String). Use atof if you want to convert a string to a float.

    - Sean
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  3. #3
    Im back! shaik786's Avatar
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    A variable declared as char is capable of storing any integer between the values: -128 to +127
    While, a variable declared as unsigned char is capable of storing any integer between the values: 0 to 255
    This kind of working is due to the fact that a 'char' consists of 8 BITS (1 BYTE), the Most Significant Bit (MSB) of which is used to represent it's sign (+ or -).
    In the case of a 'char', when this bit is set to '1', the number is assumed to be a negative number, and when '0', is assumed to be a positive number.
    But in the case of 'unsigned char', the MSB is not used for terming the number a -ve or a +ve, instead, the number is presumed always to be a +ve integer.

  4. #4
    End Of Line Hammer's Avatar
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    Originally posted by sean345
    To turn a string like argv[0] or argv[x] into a integer you can use atoi(String). Use atof if you want to convert a string to a float.
    Just to be pedantic , it's pretty unlikely that you'll want to convert argv[0] to an int, as it's the program name, not an argument.
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  5. #5
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    >I would like to know how do we cast an argv[] if I want to check
    >whether it is equal to some integer number or decimal in C ?

    Note that argv is the array containing commands on the argument line and the program name. The elements of argv are strings, so I assume you want to convert the strings to int. For that you use atoi().

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    A char variable can be either unsigned or signed depending on the compiler. So if it's signed the range is
    -128 to 127 but if unsigned the range is 0-255.

  7. #7
    Confused Magos's Avatar
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    Originally posted by shaik786
    A variable declared as char is capable of storing any integer between the values: -128 to +127
    A char is usually defined as unsigned by default, so it's range will be 0-255.
    MagosX.com

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    No, a char can be either signed or unsigned. With both compilers I use, gcc and borland, and the char is signed. You can test by running
    Code:
    #include <stdio.h>
    
    int main(void)
    {
            char c = 128;
            unsigned char uc = 128;
            signed char sc = 128;
    
            printf("c = %d\n", c);
            printf("uc = %d\n", uc);
            printf("sc = %d\n", sc);
    
            return 0;
    }
    Since just about all machines are 2 complement, if the char is signed then the 128 overflows and you get an output of c = -128.

  9. #9
    End Of Line Hammer's Avatar
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    K&R says a char being signed or unsigned is machine-dependant. I tend to believe it
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  10. #10
    Confused Magos's Avatar
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    Originally posted by Nick
    No, a char can be either signed or unsigned. With both compilers I use, gcc and borland, and the char is signed. You can test by running
    I know that. I said that a char (notice no prefix) is usually defined as unsigned, if no predefiner is specified. I didn't say that you cannot define signed char's.
    Might be me being too unclear in my post though .
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  11. #11
    Im back! shaik786's Avatar
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    char without any prefix being signed or unsigned will be defined by the compiler. Here, in my compiler, by default it is signed!

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