What is & and * operators in C?

C Programming Language > Operators and Enums in C Language > Introduction to Operator

Short Question

20646

Answer:

* Operator is used as pointer to a variable. Example: * a where * is pointer to the variable a.
& operator is used to get the address of the variable. Example: &a will give address of a.

Explanation

The "&" operator in C is the "address of" operator. It is used to obtain the memory address of a variable. For example, if you have an integer variable "x" and you want to know its memory address, you would use "&x".

The "*" operator in C is the "dereference" operator. It is used to obtain the value stored at a memory address. For example, if you have a pointer variable "p" that points to an integer and you want to know the value stored at that memory address, you would use "*p". This operator is also used in pointer declaration and function argument.

Practical Example

The address-of operator (&) in C is used to get the memory address of a variable. Here is an example:


#include <stdio.h>

int main() {
    int x = 5;
    printf("The memory address of x is: %p\n", &x);
    return 0;
}

In this example, the variable x is initialized with the value of 5, and the address of x is printed using the address-of operator and the %p format specifier. The output would be something like "The memory address of x is: 0x7ffc6f9a6b24"

The dereference operator * in C is used to get the value stored at a memory address. Here is an example:


#include <stdio.h>

int main() {
    int x = 5;
    int *ptr = &x;
    printf("The value of x is: %d\n", *ptr);
    return 0;
}

In this example, the variable x is initialized with the value of 5, the memory address of x is stored in ptr and finally, the value stored at the memory address of x is printed using the dereference operator * and the %d format specifier. The output would be something like "The value of x is: 5"

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647. What will happen if break statement is not used in switch case in C?

Answer:

Switch case statements are used to execute only specific case statements based on the switch expression.
If we do not use break statement at the end of each case, program will execute all consecutive case statements until it finds next break statement or till the end of switch case block.

If a break statement is not used in a switch case in C, the code will continue to execute the following cases until a break or the end of the switch statement is reached. This can lead to unexpected results, as multiple cases may be executed even if only one case is intended to be executed. It is important to use the break statement in each case to ensure that only the intended case is executed and to avoid fall-through.

Example

If the break statement is not used in a switch case in C, the code will continue to execute the next case statement(s) after a match is found.

For example:


switch (x) {
    case 1: 
        printf("Case 1");
    case 2: 
        printf("Case 2");
    case 3: 
        printf("Case 3");
}

If the value of x is 1, the output will be "Case 1Case 2Case 3". This is because after the first match, the code continues to execute the next case statements, instead of breaking out of the switch statement with the use of the break statement.

To avoid this problem, the break statement should be used at the end of each case block.


switch (x) {
    case 1: 
        printf("Case 1");
        break;
    case 2: 
        printf("Case 2");
        break;
    case 3: 
        printf("Case 3");
        break;
}

This way, when the program reaches the matching case, it will break out of the switch statement and will not execute any other cases.

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648. Why is default statement used in switch case in C?

Answer:

Switch case statements are used to execute only specific case statements based on the switch expression. If switch expression does not match with any case, default statements are executed by the program.

The default statement in a switch case in C is used as a catch-all for any cases that are not explicitly handled by the other case statements. It is typically used to handle unexpected input or to provide a default behavior for the switch statement. The code block associated with the default statement is executed when no other case statement's value matches the expression being evaluated.

Example


int x = 3;

switch (x) {
    case 1:
        printf("x is 1");
        break;
    case 2:
        printf("x is 2");
        break;
    default:
        printf("x is not 1 or 2");
        break;
}

In this example, if x=3 which is not handled by any of the case statement, the default statement will be executed.

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Answer:

goto statement is used to transfer the normal flow of a program to the specified label in the program. Below is the syntax for goto statement in C.


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                  <h5 class="mb-1" style="color:#194757;">650. &nbsp;What value will be assigned to the variable X if a = 10, b = 20, c = 30, d = 40 for the expression X = a/b+c*d-c?</h5>
              </a>
            </div>
                            <div class="card">
                  <div class="card-body">
                     Answer: <ul>
<li>The above arithmetic operation is performed based on the precedence of the operators.</li>
<li>In above mentioned expression, c*d will be performed first. Then, a/b, then (c*d)-c, then (a/b) + ((c*d)-c).</li>
<li>Please check the operator precedence table to know the priority and associativity of the C operators.</li>
<li>Output of the above expression is 1170.</li>
</ul>
<pre class="prettyprint">
<xmp>

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#include <stdio.h>
#include <stdlib.h>
 
int main()
{
   int a = 10, b = 20, c = 30, d = 40, X ;
 
   X = a/b+c*d-c;
   printf(" Value of X = %d\n", X);
   return 0;
}

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651. What is the value assigned to the following variables? int X1 = 13/3; int X2 = 13%3;

Answer:

int X1 = 13/3;
int X2 = 13%3;

The value of X1 is 4
The value of X2 is 1

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652. What is the difference between auto variable and register variable in C?

Answer:

Storage class of all variables are auto by default unless we specify a variable is register or static or extern in C program.

Both auto variable and register variable are local variables. Register variables are stored in register memory. Whereas, auto variables are stored in main CPU memory.
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Answer:

Both auto and static variables are local variables.
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654. Where should type cast function not be used in C?

Answer:

Type cast function should not be used in const and volatile declaration.
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Answer:

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656. What is static function in C?

Answer:

All functions are global by default in a C program/file. But, static keyword makes a function as a local function which can be accessed only by the program/file where it is declared and defined. Other programs/files can’t access these static functions.

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