Variable size and range

I am having trouble to understanding this combination to store variable. I do not understand which one should be use for specific reason
let's suppose if I want to store integer number then I have 11 ways to store integer value'

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int N;

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signed int N;

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unsigned int N;

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short int N;

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long int N;

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short  int N;

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short signed  int N;

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short unsigned  int N;

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long  int N;

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long signed  int N;

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long unsigned  int N;

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I know the difference between signed and unsigned int. if I want to store positive number I use unsigned int and if I don't know number is positive or negative then i use only int.

I think each statement has its own important. I do not understand what to use and when to use it ?

You repeated short int and long int, and the signed keyword really only matters for signed char since by default the integer types are signed. Then you omitted long long. So I'd put the list as:

Code:

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signed char
unsigned char
short
unsigned short
int
unsigned int
long
unsigned long
long long
unsigned long long

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and then there are width-specific types from <inttypes.h> that are aliases for these types above, along with other aliases like size_t and ptrdiff_t. I omitted char because it's not a good idea to use it as an integer type because whether it is signed or unsigned is implementation defined.

As for what to use: it depends on your requirements, of course. If you are unsure, default to int (or unsigned int if you know you need an unsigned integer) and perhaps use your own typedef so you can easily change it later. If you're working with sizes, consider using size_t.

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Originally Posted by laserlight

You repeated short int and long int, and the signed keyword really only matters for signed char since by default the integer types are signed. Then you omitted long long. So I'd put the list as:
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That information given on this page C syntax - Wikipedia

1. Size qualifiers – short, long
2. Sign qualifiers – signed, unsigned
3. Data types - int, char, float, double

<Sign qualifiers > <Data types>
<Size qualifiers> <Data types>
<Size qualifiers> <Sign qualifiers > <Data types>

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Originally Posted by abhi143

That information given on this page C syntax - Wikipedia

1. Size qualifiers – short, long
2. Sign qualifiers – signed, unsigned
3. Data types - int, char, float, double

[FONT="]<[/FONT][FONT="]Sign qualifiers > <[/FONT]Data types>
[FONT="]<Size qualifiers> [/FONT][FONT="]<[/FONT]Data types>[FONT="]
<Size qualifiers> <[/FONT]Sign qualifiers > <Data types>

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Can't find that on that page. What I did find, under Data structures -> Primitive data types -> Integer types, was the statement that "In many cases, there are multiple equivalent ways to designate the type; for example, signed short int and short are synonymous." and a "Specifications for standard integer types" table that is identical to mine except that it includes _Bool and char.

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Originally Posted by laserlight

Can't find that on that page. What I did find, under Data structures -> Primitive data types -> Integer types,ard integer types" table mine except that it includes _Bool and char.

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What you said in post 2 is given in page integer types" table

suppose we want to store number -32768 to 32767

Code:

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#include<stdio.h> int main(void)
{   
  short a = 32767;
  printf("max number = %d \n", a); 
  printf ("size of a = %d", sizeof (a));   
  return 0;
}

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max number = 32767
size of a = 2

in my example, I am just using qualifier to store data but I haven't used data type

I still don't know what to use and when it should use ?

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Originally Posted by abhi143

in my example, I am just using qualifier to store data but I haven't used data type

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The data type is named short. It is an alias for short int and for signed short int. If you cannot get your head around this, then use my table as the sole truth and forget that you ever heard about short int (unless you do see it in the wild, then just aggressively delete the "int" and move on).

Quote:

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Originally Posted by abhi143

I still don't know what to use and when it should use ?

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I thought you were talking about selecting relevant data types. If your concern is just about the type names and their aliases, then as I said, use my table from post #2 as your sole source of truth concerning the integer type names. If Wikipedia tells you something else that you think is contradictory, forget it as I'm more authoritative than Wikipedia (seeing that I can change Wikipedia by citing the standard).