Boolean and Static in C Programming With Examples ( Full Guide )

Boolean and Static in C: An Overview

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Boolean in C

The bool data type is one of the fundamental data types in C. It is used to hold only two values i.e. true or false. The C program returns boolean values as integers, 0 and 1. The boolean meaning of these integers are:

• 0 indicates a false value
• 1 (or any other number not equal to 0) indicates true value.

As they return boolean values, we need to use the format specifier, “%d” to print the boolean values.

Syntax

bool variable_name;

The “bool” keyword is used to declare boolean variables.

Example

#include <stdio.h> 
#include <stdbool.h> 
int main() 
{ 
 bool x=false, y=true; // variable initialization.
 printf("%d\n",x);
 printf("%d\n",y); 
 return 0; 
} 

In the above code in the C Compiler, the boolean variables, x, and y are initialized with the value, “false” and “true” respectively. The code prints the boolean values as integers.

Output

0
1

Read More - Top 50 Mostly Asked C Interview Questions

How to use a boolean in C?

1. Boolean variables: the user can declare Boolean variables to store Boolean values. For example:

   #include <stdbool.h>
   bool isSunny = true;
   bool isRaining = false;
   

2. Boolean expressions: the user can use Boolean expressions to evaluate conditions and make decisions in their code. For example:

   if (isSunny && !isRaining) {
    printf("It's a perfect day for a picnic!\n");
   }

   The above code uses an if statement to check the condition. The test expression uses the logical operator, && to evaluate the condition. If the test expression results in the boolean value, “true”; the if statement will be executed. The use of booleans in decision-making and looping statements will be seen in the upcoming sections.

3. Boolean functions: The developer can write boolean functions that return true or false depending on some condition. For example:

   bool isEven(int num) {
    return (num % 2 == 0);
   }
   

   In the above code, the function isEven() returns a boolean value in C. You will get more clarity on functions in the section, Functions in C.

4. Boolean arrays: the user can use boolean arrays to store a collection of boolean values in C. For example:

   bool weekdays[7] = { true, true, true, true, true, false, false };
   

   The above code declares an array of size 7. The array stores 7 boolean values, “true” and “false”. We use the for loop and indexing to access these values. When we will study arrays in the section Arrays in C, you will get more ideas regarding this example.

What is Static in C?

Static in C is a keyword to indicate a particular memory location that remains occupied during the program’s lifetime. In essence, defining something as static makes it available throughout the entire program, which is particularly useful when wanting to keep values persistent between function calls.

Static variables enable data to remain after the function has been executed and returned; this allows the function to remember a value from a previous call, making them both efficient and powerful.

How to use static keywords in C?

The static keyword can be used with both variables and functions.

1. Static variable

Syntax

static data_type variable_name;

• Static Global Variable

Example

#include <stdio.h>
static char c;
static int i;
static float f;
static char s[100];
int main ()
{
printf("%c %d %f %s",c,i,f,s); // the default values of c, i, f, and s will be printed.
return 0;
}

Output

0 0 0.000000 (null)

• Static Local Variable

Example

#include <stdio.h>
int main()
{ printf("%d",function());
 printf("\n%d",function());
 return 0;
}
int function()
{ static int count=0;
 count++;
 return count;
}

In the above code, the count variable is a static variable. When the function, “function()” is called first time, the value of count increments to 1, and during the next function call, the value of the count variable becomes 2.

Output

1 
2

• Static member variables

2. Static Function

Example

#include<stdio.h>

static void function() 
{ 
 printf("Welcome to the ScholarHat"); 
}

int main() {
 function(); 
 return 0;
}

The above code in the C Editor creates a static function named function(). This function() is called by the main function.

Output

Welcome to the ScholarHat

3. The Static Method

The member function of a class declared with a static keyword is known as a static method. It is accessible to all the instances of a class and not only to a specific instance.

Summary