Reusability and maintenance - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Modular Function Calls

What is the output of this C program that uses a reusable function to calculate the square of a number?

C

#include <stdio.h>

int square(int x) {
    return x * x;
}

int main() {
    int a = 3, b = 4;
    printf("%d %d\n", square(a), square(b));
    return 0;
}

A 9 16

B 3 4

C 6 8

D 12 16

💡 Hint

Remember the function returns the square of the input.

The function square multiplies the input by itself. So square(3) is 9 and square(4) is 16.

❓ Predict Output

intermediate

Output of Code Using Header File Inclusion

Given the following files, what will be the output when compiled and run?

math_ops.h
int add(int x, int y);

math_ops.c
int add(int x, int y) { return x + y; }

main.c
#include
#include "math_ops.h"
int main() {
printf("%d\n", add(5, 7));
return 0;
}

A Runtime error

B 57

C 12

D Compiler error due to missing function definition

💡 Hint

Check if the function is properly declared and defined.

The function add is declared in the header and defined in math_ops.c. When linked properly, it returns 5 + 7 = 12.

🔧 Debug

advanced

Identify the Cause of Unexpected Output

What causes the unexpected output in this C program that tries to reuse a function to increment a value?

#include <stdio.h>

void increment(int x) {
    x = x + 1;
}

int main() {
    int a = 5;
    increment(a);
    printf("%d\n", a);
    return 0;
}

A The printf statement has wrong format specifier

B The function is missing a return statement

C The variable 'a' is not initialized

D The function increments a copy of the variable, not the original

💡 Hint

Think about how arguments are passed to functions in C.

In C, function arguments are passed by value, so increment changes only a copy of a. The original a remains unchanged.

📝 Syntax

advanced

Identify the Syntax Error in Modular Code

Which option contains the syntax error that prevents this modular C code from compiling?

#include <stdio.h>

int multiply(int x, int y) {
    return x * y
}

int main() {
    printf("%d\n", multiply(3, 4));
    return 0;
}

A Missing semicolon after return statement in multiply function

B Missing return type for multiply function

C Missing parentheses in printf call

D Missing main function return statement

💡 Hint

Check punctuation carefully in function bodies.

The return statement in multiply lacks a semicolon, causing a syntax error.

🚀 Application

expert

Number of Functions in a Modular Program

Consider a C program split into three files: main.c, utils.c, and math.c. utils.c has 4 functions, math.c has 3 functions, and main.c has 2 functions. How many functions are available for reuse across the entire program after linking?

A 3

B 9

C 7

D 2

💡 Hint

Count all functions defined in all files.

All 4 + 3 + 2 functions are compiled and linked, so 9 functions are available for reuse.