Explain about Formatted Input in detail with the prototype of ‘scanf’’ function in C programming

scanf() function

v The scanf() function id formatted input function it depends on Format specifiers.

v The scanf() function is used to read multiple data values of different data types from the keyboard.

v The scanf() function is built-in function defined in a header file called "stdio.h". When we want to use scanf() function in our program, we need to include the respective header file (stdio.h) using #include statement.

Syntax:

scanf("format strings",&variableNames);

Format string: %d, %c, %f, %s has been use as format string.

Variable list: Name of variable followed by address operator where input though keyboard been transferred.
Example

scanf(%d”,&a);---------->Integer input

scanf(“%c”,&a);---------> character input

scanf(“%f”,&a);---------> float input

scanf(“%s”,&a);---------> string input

Space will not be accept through keyboard

Scanf("%d%d%s", &a, &b, &c);

Example Program

#include<stdio.h>

int main()

{

int i;

printf("\nEnter any integer value: ");

scanf("%d",&i);

printf("\nYou have entered %d number",i);

return 0;

}

Output:

1. Constants and types of constants with examples

Definition:

A constant is a named memory location which holds only one value throughout the program execution.

Types of Constants:

1. Integer constants

2. Floating Point constants

3. Character Constants

4. String Constants

Integer constants

v An integer constant can be a decimal integer or octal integer or hexadecimal integer.

v A decimal integer value is specified as direct integer value whereas octal integer value is prefixed with 'o' and hexadecimal value is prefixed with 'OX'.

Floating Point constants

v A floating-point constant must contain both integer and decimal parts.

v Some times it may also contain the exponent part. When a floating-point constant is represented in exponent form, the value must be suffixed with 'e' or 'E'.

Example

Float f=3.14

The floating-point value 3.14 is represented as 3E-14 in exponent form.

Character Constants

A character constant is a symbol enclosed in single quotation. A character constant has a maximum length of one character.

Example

char ch='A';

char b='2';

char c='m';

String Constants

A string constant is a collection of characters, digits, special symbols and escape sequences that are enclosed in double quotations.

Example:

Char name [30] =”Hi How r u?”

Explain the precedence and associativity rules of operators help in executing a ‘C’ expression with an example.

C Operator Precedence and Associativity

Operator Precedence:

Operator precedence is used to determine the order of operators evaluated in an expression. In c programming language every operator has precedence (priority). When there is more than one operator in an expression the operator with higher precedence is evaluated first and the operator with the least precedence is evaluated last.

Example:

10 + 4 * 3 / 2

In the above expression, there are three operators +, * and /. Among these three operators, both multiplication and division have the same higher precedence and addition has lower precedence. So, according to the operator precedence both multiplication and division are evaluated first and then the addition is evaluated. As multiplication and division have the same precedence they are evaluated based on the associativity. Here, the associativity of multiplication and division is left to right. So, multiplication is performed first, then division and finally addition. So, the above expression is evaluated in the order of * / and +. It is evaluated as follows...

4 * 3 ====> 12
12 / 2 ===> 6
10 + 6 ===> 16
the expression is evaluated to 16.

Operator Associativity:

Operator associativity is used to determine the order of operators with equal precedence evaluated in an expression. In the c programming language, when an expression contains multiple operators with equal precedence, we use associativity to determine the order of evaluation of those operators.

Let us try to evaluate an arithmetic expression as shown below:

x = a-b/3+c*2-1

Let a = 9, b =12, and c=3. Then our expression becomes:

x = 9-12/3+3*2-1

From the above table, we can see that the * and / operators are having higher precedence than + and – operators. Also, the * and / operators are at the same level of precedence, so we have to apply the associativity rules. Since the associativity rule is left-to-right, we apply the / operator first and the expression evaluates to:

x = 9-4+3*2-1

Next, we apply the * operator and the expression becomes:

x = 9-4+6-1

Next, we apply the first – operator as the – and + operators are at the same level and the associativity rule is from left to right. The expression becomes:

x = 5+6-1

Now, we apply the + operator and the expression become:

x = 11-1

Finally, we apply the – operator and the result is:

x = 10