Below is the program in C Language that will take decimal number as input. It will then call a function that will calculate the binary equivalent of the input decimal number.

#include
#include

int i = 0;
int b[10];

void main()
{
    int dec;
    int* DecimalToBinary(int n);
    int *p, j;
    
    printf("Enter a decimal integer = ");
    scanf("%d", &dec);
    
    p = DecimalToBinary(dec);
    
    printf("Binary of given decimal integer = ");
    for (j=i; j>=0; j--)
    	printf("%d", p[j]);
    
    printf("\n");
    
    getch();
}
    
int* DecimalToBinary(int n)
    {
    while (n != 1)
    {
        b[i] = n % 2;
        n = n / 2;
        i++;
    }
    
    if (n == 1)
    {
    	b[i] = 1;
    }
    else
    {
    	b[i] = 0;
    }
    
    return b;
}