help on declarations

This is a discussion on help on declarations within the C Programming forums, part of the General Programming Boards category; I am working on trying to declarations and using typedef. this is my assignment Write and compile a program in ...

  1. #1
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    help on declarations

    I am working on trying to declarations and using typedef.
    this is my assignment
    Write and compile a program in C to declare data variables of each of following types: unsigned char, unsigned short, unsigned int, unsigned long int. Use Typedef. Use meaningful names for type definitions. Declare a data variable for each of the type definitions and initialize them with 255, 65535 and 4294967295 respectively. Write the comments for each declaration.

    I have used typedef to remame declarations but now after I declare a variable it will not compile.

    please the my attachment for what I wrote

    I get a compiler log error like this:

    Compiler: Default compiler
    Executing g++.exe...
    g++.exe "C:\Documents and Settings\dustin\My Documents\computer programming class\typedef.cpp" -o "C:\Documents and Settings\dustin\My Documents\computer programming class\typedef.exe" -traditional-cpp -g3 -I"C:\Dev-Cpp\include\c++" -I"C:\Dev-Cpp\include\c++\mingw32" -I"C:\Dev-Cpp\include\c++\backward" -I"C:\Dev-Cpp\include" -L"C:\Dev-Cpp\lib" -g3
    C:/Documents and Settings/dustin/My Documents/computer programming class/typedef.cpp: In
    function `int main()':
    C:/Documents and Settings/dustin/My Documents/computer programming class/typedef.cpp:10: parse
    error before `=' token

    C:/Documents and Settings/dustin/My Documents/computer programming class/typedef.cpp:10:11: warning: multi-character character constant

    Execution terminated

    I have no clue what I am doing wrong can someone point me in the right direction thank you.
    Attached Files Attached Files
    Last edited by robasc; 03-05-2005 at 09:00 AM.

  2. #2
    C Programmer Stack Overflow's Avatar
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    Hello,

    All variables must be declared before use, although certain declarations can be made implicitly by context. A declaration specifies a type, and contains a list of one or more variables of that type as in:
    Code:
    int a, b, c;
    char s, l;
    char m = 'a';
    If this makes sense, then you may find that:
    Code:
    char = 'h';
    Is an invalid declaration.


    - Stack Overflow
    Segmentation Fault: I am an error in which a running program attempts to access memory not allocated to it and core dumps with a segmentation violation error. This is often caused by improper usage of pointers, attempts to access a non-existent or read-only physical memory address, re-use of memory if freed within the same scope, de-referencing a null pointer, or (in C) inadvertently using a non-pointer variable as a pointer.

  3. #3
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    I still do not understand.
    I am very new at this, so perhaps you could simplify this a little more for me to understand.

  4. #4
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    typedef is used to create something like a synonym to the data type.
    Code:
     typedef int num1;
    then you can use num1 to declare variables as int as follows
    Code:
    num1 x, y;
    which is equivalent to
    Code:
    int x, y;
    When no one helps you out. Call google();

  5. #5
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    Code:
    So I could develope this
    
    typedef unsigned char u_char
    int main(){
    u_char = '255';
    }

  6. #6
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    With typedef you are creating a new type, like an int, float, etc.
    You can think of typedef like this:
    whenever you do
    Code:
    u_char a = 'b';
    the compiler will treat it as
    Code:
    unsigned char a = 'b';
    so u_char

  7. #7
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    Wow! This is very confusing

    Ok, I understand that I can use typedef to redefine unsigned char to u_char, intern this is simplifying the term unsigned char, like this
    Code:
     
    typedef unsigned char u_char;
    is this correct?

    now

  8. #8
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    yes, now you can use u_char to declare variables as unsigned char
    When no one helps you out. Call google();

  9. #9
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    Now the next thing I need to do is this

    Use meaningful names for type definitions. Declare a data variable for each of the type definitions and initialize them with 255, 65535 and 4294967295 respectively. Write the comments for each declaration.


    Code:
    typedef unsigned char  u_char;
    /* define unsigned char as u_char */
    typedef unsigned short u_short;
    /* define unsigned short as u_short */
    typedef unsigned int u_int;
    /* define unsigned int as u_int */
    typedef unsigned long int ul_int;
    /* define unsigned long int as ul_int */
    int main(){
        u_char name = 255;
        u_short Squarfeet = 65535;
    
        
        
    
     }
    is this correct?

  10. #10
    ATH0 quzah's Avatar
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    Deja Vu!

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

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