Function

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To create a function in C, define it with a return type, name, parameters, and body.

Project 1

#include <stdio.h>
void swap(int a, int b)
{
    int tmp;
    tmp = a;
    a = b;
    b = tmp;
    printf("In swap : A = %d, B = %d\n", a, b);
}
int main()
{
    int a = 5, b = 10;
    printf("Before swap A = %d, B = %d\n", a, b);
    swap(a, b);
    printf("After swap A = %d, B = %d\n", a, b);
}

Output :

Before swap A = 5, B = 10
In swap : A = 10, B = 5
After swap A = 5, B = 10

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Project 2

#include <stdio.h>
int myFactorial(int);

int main()
{
    int myNumber = 10;
    printf("%d ! is %d\n", myNumber, myFactorial(myNumber));
}
int myFactorial(int n)
{
    int result = 1, i;
    for (i = 1; i <= n; i++)
    {
        result *= i;
    }
    return result;
}

Output :

10 ! is 3628800

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Project 3

#include <stdio.h>

void myCal(int x){
    if(x < 0){
        printf("f(%d) = 0 \n",x);
    }else{
        printf("f(%d) = %d\n",x,(x*x+2*x+1));
    }
}
int main(){
    int number;
    printf("Enter x : ");
    scanf("%d",&number);
    myCal(number);
}

Output :

Enter x : 10
f(10) = 121

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Project 4

#include <stdio.h>

int maxinum(int arr[]){
    int max = arr[0];
    for (int i = 1; i < 8; i++) {
        if (arr[i] > max) {
            max = arr[i];
        }
    }
    return max;
}
int main(){
    int arr[8] = {8,4,-3,3,17,-1,-5,10};
    int max_value = maxinum(arr);
    printf("Maximum value is %d\n", max_value);
    return 0;
}

Output :

Maximum value is 17

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Project 5

#include <stdio.h>

float average(int a, float x[]) {
    float avg, sum = 0;
    for (int i = 0; i < a; i++) {
        sum += x[i];
    }
    avg = sum / a;
    return avg;
}
int main() {
    int count;
    printf("Number of students N = ");
    scanf("%d", &count);
    float arr[count], averageNum;
    for (int i = 0; i < count; i++) {
        printf("Enter score %d : ", i + 1);
        scanf("%f", &arr[i]); 
    }
    averageNum = average(count, arr);
    printf("Average score is %.2f\n", averageNum);
    return 0;
}

Output :

Number of students N = 3
Enter score 1 : 10
Enter score 2 : 20
Enter score 3 : 30
Average score is 20.00

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Project 6

#include <stdio.h>
int i = 0;
void disp(int i);
void show();
int main()
{
    int i = 9;
    printf("i in main function = %d\n", i);
    disp(3);
    show();
}
void disp(int i)
{
    i = 5;
    printf("i in function disp = %d\n", i);
}
void show()
{
    printf("i in function show = %d\n", i);
}

Output :

i in main function = 9
i in function disp = 5
i in function show = 0

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Project 7

#include <stdio.h>

int a = 20;
int sum(int b);
int main()
{
    int a = 10;
    int b = 20;
    int c = 0;
    printf("value of a in main() = %d\n", a);
    c = sum(b);
    printf("value of c in main() = %d\n", c);
}
int sum(int b)
{
    printf("value of a in sum() = %d\n", a);
    printf("value of b in sum() = %d\n", b);
    return a + b;
}

Output :

value of a in main() = 10
value of a in sum() = 20
value of b in sum() = 20
value of c in main() = 40