RAGGED ARRARY

The two-dimensional array character type arrays occupy a fixed amount of memory space for each row that is rarely needed .Therefore , instead of making each row fixed number of characters . We can make it a pointer to a string of varying length.

The character Arrays with the rows of varying length are called "RAGGED ARRAY " and are better handled by pointer . For example :

char *cname[3] = {"india", "nepal" ,"bhutan"}; // is the declaration and intialisation of Ragged Array.

POINTER

BASE ADDRESS AND CONSTANT POINTER :- When an array (any data type ) is declared , the compiler allocate a base address and sufficient amount of storage to contain all the element of the array in contiguous location .The BASE ADDRESS is the location of the first element( index 0) of the array .The compiler also defines the array name as a CONSTANT POINTER to the first element .Example int num = {12 , 5 , 107 , 55 , 291 } -- here an int type array num is declared and "num" is the constant pointer that denotes the base address of &num[0].

SCALE FACTOR

When we increment a pointer , its value is increased by the length of the data type that it points to .this length is called SCALE FACTOR .[i,e.ptr = ptr + 1 or ptr++].The no of bytes used to stored various data types can be found by making use of "SIZE OF" operator . For example , if X is a variable , the size of (X) returns the number of bytes needed for the variable.

SOME C DEFINITION

1.POINTER VALUE : It is the variable address the pointer contains and the VALUE THE POINTER to is the content of that variable whose address stored in the pointer .The "&" operator can be remembered as ADDRESS OF and the indirection operator "*" can be remembered as VALUE AT ADDRESS .We use "%u" format for printing Address values as Memory address are Unsigned Integers.

CALL BY REFENCE.

swapping the two no.

void main()

{

void myudf(int * , int *); //function declaration ....ansi or modern style.....

int nx , ny ;

int *px , *py ;

px = &nx ;

py = &ny ;

printf("ENTER TWO NO.S ") ;

scanf("%d %d" , px ,py);

myudf(px , py); // funtion calling.....................

printf("BACK TO MAIN: THE FISRT NO IS[%d] AT ADDR [u] SECOND IS :[%d] AT ADDR [%u] " , *px , px , *py , py );

getch();

}

//............END OF MAIN............................

void myudf( int *pnx , int *pny)

{

int z ;

z = *pnx ;

*pnx = *pny ;

*pny = z ;

printf("AT UDF : NOW THE FIRST NO. IS:[%d]AT ADDR [%u] THE SECOND NO.[%d] AT ADDR [%u] " ,*pnx , pnx , *pny , pny );

getch();

}

c programing

1. main()

{

char string[]="Hello World";

display(string);

}

void display(char *string)

{

printf("%s",string);

}

Answer:

Compiler Error : Type mismatch in redeclaration of function display

Explanation :

In third line, when the function display is encountered, the compiler doesn't know anything about the function display. It assumes the arguments and return types to be integers, (which is the default type). When it sees the actual function display, the arguments and type contradicts with what it has assumed previously. Hence a compile time error occurs.

2. main()

{

int c=- -2;

printf("c=%d",c);

}

Answer:

c=2;

Explanation:

Here unary minus (or negation) operator is used twice. Same maths rules applies, ie. minus * minus= plus.

Note:

However you cannot give like --2. Because -- operator can only be applied to variables as a decrement operator (eg., i--). 2 is a constant and not a variable.

3. #define int char

main()

{

int i=65;

printf("sizeof(i)=%d",sizeof(i));

}

Answer:

sizeof(i)=1

Explanation:

Since the #define replaces the string int by the macro char

4. main()

{

int i=10;

i=!i>14;

Printf ("i=%d",i);

}

Answer:

i=0

Explanation:

In the expression !i>14 , NOT (!) operator has more precedence than ‘ >’ symbol. ! is a unary logical operator. !i (!10) is 0 (not of true is false). 0>14 is false (zero).

5. #include

main()

{

char s[]={'a','b','c','\n','c','\0'};

char *p,*str,*str1;

p=&s[3];

str=p;

str1=s;

printf("%d",++*p + ++*str1-32);

}

Answer:

77

Explanation:

p is pointing to character '\n'. str1 is pointing to character 'a' ++*p. "p is pointing to '\n' and that is incremented by one." the ASCII value of '\n' is 10, which is then incremented to 11. The value of ++*p is 11. ++*str1, str1 is pointing to 'a' that is incremented by 1 and it becomes 'b'. ASCII value of 'b' is 98.

Now performing (11 + 98 – 32), we get 77("M");

So we get the output 77 :: "M" (Ascii is 77).

6. #include

main()

{

int a[2][2][2] = { {10,2,3,4}, {5,6,7,8} };

int *p,*q;

p=&a[2][2][2];

*q=***a;

printf("%d----%d",*p,*q);

}

Answer:

SomeGarbageValue---1

Explanation:

p=&a[2][2][2] you declare only two 2D arrays, but you are trying to access the third 2D(which you are not declared) it will print garbage values. *q=***a starting address of a is assigned integer pointer. Now q is pointing to starting address of a. If you print *q, it will print first element of 3D array.

7. #include

main()

{

struct xx

{

int x=3;

char name[]="hello";

};

struct xx *s;

printf("%d",s->x);

printf("%s",s->name);

}

Answer:

Compiler Error

Explanation:

You should not initialize variables in declaration

8. #include

main()

{

struct xx

{

int x;

struct yy

{

char s;

struct xx *p;

};

struct yy *q;

};

}

Answer:

Compiler Error

Explanation:

The structure yy is nested within structure xx. Hence, the elements are of yy are to be accessed through the instance of structure xx, which needs an instance of yy to be known. If the instance is created after defining the structure the compiler will not know about the instance relative to xx. Hence for nested structure yy you have to declare member.

9. main()

{

printf("\nab");

printf("\bsi");

printf("\rha");

}

Answer:

hai

Explanation:

\n - newline

\b - backspace

\r - linefeed

10. main()

{

int i=5;

printf("%d%d%d%d%d%d",i++,i--,++i,--i,i);

}

Answer:

45545

Explanation:

The arguments in a function call are pushed into the stack from left to right. The evaluation is by popping out from the stack. and the evaluation is from right to left, hence the result.