Review C: C for Python programmers

Problem C1.1

What distinguishes a compiler from an interpreter?

Problem C1.2

C is called a procedural language. Why is procedural an apt adjective? (Saying basically that C is not object-oriented is not an adequate answer.)

Problem C2.1

Complete the below C function so that it returns the nth harmonic number for a parameter n. The nth harmonic number is the sum

∑_i = 1ⁿ (1 / i) = 1/1 + 1/2 + 1/3 + … + 1/(n − 1) + 1/n double harmonic(int n) {

Problem C2.2

The following series computes the value of π.

π = ∑_n = 0^∞ 8 / [(4 n + 1) (4 n + 3)] = 8 / (1 ⋅ 3) + 8 / (5 ⋅ 7) + 8 / (9 ⋅ 11) + 8 / (13 ⋅ 15) + ….

Complete the C program below to display the result of adding as many terms of the series as requested by the user. For example, given the input 1, the program should display 2.6667 ≈ 8/3; given 2, it should display 2.8952 ≈ 8/3 + 8/35; given 3, it should display 2.9760 ≈ 8/3 + 8/35 + 8/99.

int main() {
    int terms;
    double pi;


    printf("Number of terms: ");
    scanf("%d", &terms);




    printf("%6.1f", pi);
    return 0;
}

Problem C2.3

Write a C function count_common_factors that given two integer parameters m and n returns the number of integers that are factors both of m and n. For example, count_common_factors(70, 28) should return 4 since there are four distinct integers dividing into both (1, 2, 7, 14). The below code illustrates how this might be done using Python.

def count_common_factors(m, n):
    count = 0
    for i in range(1, m + 1):
        if m % i == 0 and n % i == 0:
            count += 1
    return count

Problem C2.4

The hailstone sequence is defined by the following loop.

while n ≠ 1:
    if n is odd:
        n ← 3 n + 1
    else:
        n ← n / 2

Starting with 7, this loop iterates n through a sequence of 17 numbers:

7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1.

If we started with 5, the sequence would contain just six numbers — 5, 16, 8, 4, 2, 1.

Complete the following function so that it returns how many numbers are in the hailstone sequence starting from its parameter; thus, hailstone(7) should return 17 while hailstone(5) returns 6.

int hailstone(int start) {

Problem C2.5

The following program has already been written to populate its data array with 100 values entered by the user. Complete the program so that it displays all positive numbers in the array in reverse order (skipping over all non-positive numbers), each on its own line. For example, if the array was length 6 rather than 100, and the user entered <4, 3, −1, −2, −6, 5>, your code would display 5, then 3, then 4.

int main() {
    int data[100];
    int i;

    for (i = 0; i < 100; i++) {
        printf("Value %d: ", i + 1);
        scanf("%d", &(data[i]))
    }

Problem C2.6

The following program has already been written to populate its data array with 10 values entered by the user. Using a loop, complete the program so that it displays “palindrome” if the array is the same read backwards as forwards (as in <9, 13, 15, 15, 13, 9>, which reversed is the same) and “no” otherwise.

int main() {
    int data[10];
    int i;

    for (i = 0; i < 10; i++) {
        printf("Value %d: ", i + 1);
        scanf("%d", &(data[i]))
    }

Problem C3.1

Explain the motivation behind using a header file for a C program.