Question

The program in C language

PQ1. How would you declare the following scalar and non-scalar (vector) variables?

1. counter, an integer
2. sum, a decimal number
3. average, a decimal number
4. grades, an array of 32 decimal numbers

PQ2.

1. How would you initialize the array above with numbers between 0.0 and 4.0 representing the grades of all courses a senior has received in the four years of college?
2. Instead of initializing the array above, how would you, in a loop, accept input from the user for the 32 grades?

PQ3.

1. How would you calculate the sum of all the grades in the array above?
2. How would you average the sum above?

PQ4. The algorithm for checking if a number is a prime is to check if it is divisible by any number less than itself other than 1. (Divisibility implies that if you use the modulus operator, %, the result will be 0). Write a function to check if a number is a prime.

Answer 1

PQ1:

int counter;

This is how you declare an integer variable named counter.

In general to declare an integer by the name variable_name , the syntax is int variable_name;

double sum;

This is how you declare a decimal number named sum.

In general to declare a decimal number by the name variable_name , the syntax is double variable_name;

Similarly for decimal number average we declare it as

double average;

There is another data type that can also be used instead of double namely float but double carries with it the advantage of being 2x more precise in the fractional part as compared to float.

double grades[32];

This is the way to declare an array of 32 decimal numbers , wherein the first grade can be accessed using grades[0], second by grades[1] and so on until the 32nd grade can be accessed by grade[31]. This shows that arrays are 0-indexed in C.

In general to declare an array of decimal numbers of size n , we simply write double array_name[n];

PQ2

To initialize the above grades array we use the following syntax:

double grades[32] = {2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5 };

Simply place 32 decimal numbers inside brackets to initialize the array.

The simplest way to initialize the array.

But most often in practical programs , this is not the case and it is the user who provides the contents of the array.In such cases following is the way to implement it:

for(int i=0;i<32;i++){

          scanf("%lf",&grades[i]);

}

This is how you use a for loop to accept grades from the user and store them in the array.

The program which uses the first approach to initializing arrays and prints the contents of the array:

#include<stdio.h>

int main(){

   double grades[32] = {2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5, 2.0, 3.0, 4.0, 2.5,2.0, 3.0, 4.0, 2.5 };

   for(int i=0;i<32;i++){
       printf("%lf ",grades[i]);
   }
   printf("\n");

   return 0;

}

OUTPUT:

The program which uses the second approach to initializing arrays and prints the contents of the array:

#include<stdio.h>

int main(){

   printf("Please enter 32 grades: ");

   double grades[32];
   for(int i=0;i<32;i++){
      
              scanf("%lf",&grades[i]);

   }
   for(int i=0;i<32;i++){
       printf("%lf ",grades[i]);
   }
   printf("\n");

   return 0;

}

OUTUPUT:

PQ3

To calculate the sum of grades array we can just use a for loop and store the sum of contents of the decimal numbers in a decimal variable sum.

double sum = 0;

for(int i=0;i<32;i++){

       sum = sum+grades[i];

}

After this iteration sum contains the sum of all grades of array.

The program which calculates sum over the grades array and prints the sum:

#include<stdio.h>

int main(){

   printf("Please enter 32 grades: ");

   double grades[32];
   for(int i=0;i<32;i++){
      
              scanf("%lf",&grades[i]);

   }
   double sum = 0;

   for(int i=0;i<32;i++){

           sum = sum+grades[i];

   }

   printf("The sum of the grades is: %lf\n",sum);

   return 0;

}

OUPTUT:

The average can be easily computed using the sum previously calculated and by dividing it simply by 32.0

double average = sum/32.0;

Now average stores the average of grades of the array.

The program which calculates average over the grades array and prints the average:

#include<stdio.h>

int main(){

   printf("Please enter 32 grades: ");

   double grades[32];
   for(int i=0;i<32;i++){
      
              scanf("%lf",&grades[i]);

   }
   double sum = 0;

   for(int i=0;i<32;i++){

           sum = sum+grades[i];

   }

   double average = sum/32.0;
   printf("The average of the grades is: %lf\n",average);

   return 0;

}

OUTPUT:

In PQ2 and PQ3 programs and output have been provided just for understanding purposes.

PQ4

#include<stdio.h>

int isPrime(int n){
    //HANDLING BASE CASE THAT 1 IS NEITHER PRIME NOR COMPOSITE.

    if(n==1)return 0;

   int check = 1;
   //CHECK IF n IS DIVISIBLE BY ANY NUMBER BETWEEN 2 AND N-1(INCLUSIVE)
   //IF SO THEN n IS NOT PRIME AND THUS SET CHECK = 0 AND BREAK
   for(int i=2;i<n;i++){
       if(n%i == 0){
           check = 0;
           break;
       }
   }

   //IF CHECK IS 1 STILL IT MEANS THERE IS NO NUMBER OTHER THAN 1 AND n THEMSELVES
   //WHICH DIVIDE n THUS n IS PRIME ELSE NOT
   return check;
}

int main(){
   int n;
   printf("Enter a number to be checked if it is prime or not:");      
   scanf("%d",&n);
   if(isPrime(n)==1){
       printf("The entered number is prime\n");
   }else{
       printf("The entered number is not prime\n");
   }
   return 0;

}

OUTPUT: