Types, Operators, and Expressions

signed s;
unsigned u;
long l;
long long ll;

short int n;

long int m;

//the word int can be omitted -

short n;

long m;

Octal and Hex constants may be followed by U or L suffix to make them unsigned or long respectively.

0xFUL  // this is a unsigned long hex with value 15 in decimal 

'\0' has an ASCII value of 0.
'0' has an ASCII value of 48 which is unrelated to zero.

'\013' - Octal Number

'\xAF' - Hex Number

A character constant 'a' is not the same as "a", the former has an integer value internally and the latter is delimited by a null character ('\0') character.

#define MAX
int p = MAX + 1;

//These are evaluated at the compile-time.

#include<stdio.h>

int main()
{
	enum my {hs, ho};	//By default, first name in an enum has value = 0, second one has value = 1 and so on...
	printf("%d\t", he);
	printf("%d", ho);
	return 0;
}	

OUTPUT: 0	1

#include<stdio.h>

int main()
{
	enum my {JAN = 23, FEB, MAR, APR, MAY};
	printf("%d\t", JAN);
	printf("%d\t", FEB);
	printf("%d\t", MAR);
	printf("%d\t", APR);
	printf("%d\t", MAY);

	return 0;
}

OUTPUT: 23	23	25	26	27

const int p = 5;
//OR
int func(const ch[]);	 //ch's values cannot be changed by func()

if(!valid)		//if not valid

//OR

if(valid == 0)	//if valid is false

Cast Operators -

(type-name) expression

Ex - 

(float) 4/2;

(unsigned int) 4.3 - 2;

x << 2 	//shifts left by two positions (equivalent to multiplying by 4)

#include<stdio.h>	
int main()
{
	int p = 3;

	printf("%d\n", ~p); 


	return 0;
}

OUTPUT: -4

i = i + 2;

//can be written as

i += 2;			//+= is an assignment operator

#include<stdio.h>	
int main()
{
	char p = 'a';
	int x;
	p += x;
	printf("%d\n", sizeof(p)); 
	return 0;
}

OUTPUT: 1

a > b? max=a : max=b;

//can also be written as - 

max = a > b? a : b;

// assume f is float and n is int

(n > 0)? f : n;

//result will be float no matter if the condition is true or not.

//Be careful in -

if((x & MASK) == 0) ...

x = f() + g();		//not sure which ammong f() or g() is evaluated first

//AND

printf("%sd %d\n", ++n, power(2, n));	//Different compiler, different results, based on what is evaluated first

a[i] = i++;	 //Subscript is the old value of i or new?

//Ans - Compilers can interpret it in different ways and generate different answers based on the interpretation.