help on declarations

**robasc** · 03-05-2005

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.

**Stack Overflow** · 03-05-2005

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

**robasc** · 03-05-2005

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

**InvariantLoop** · 03-05-2005

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;

**robasc** · 03-05-2005

Code:

So I could develope this

typedef unsigned char u_char
int main(){
u_char = '255';
}

**Yasir_Malik** · 03-05-2005

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

**robasc** · 03-05-2005

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

**InvariantLoop** · 03-05-2005

yes, now you can use u_char to declare variables as unsigned char

**robasc** · 03-05-2005

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?

**quzah** · 03-05-2005

Deja Vu!

Quzah.

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