Module design

Design the skeleton of the helper library module.

Project: Helper library

In this five-lesson project you'll build a helper library. Each lesson adds a piece; by the final lesson you'll have a program that calls every helper.

You'll use what you learned in earlier groups: pointers, dynamic memory and string handling. Throughout the project you'll define six helper functions: str_len, str_is_empty, num_abs, num_sign, arr_max and arr_sum. In this first lesson you'll lay out the module skeleton: header declarations and main.

Header file structure

A header file holds function declarations (prototypes). A declaration is the function signature terminated with a semicolon: int str_len(const char *s);.

Here const char *s says the parameter won't be modified. You can write several declarations one after another; each ends with a semicolon. Declarations tell the compiler the function exists; definitions may live in another file. This split enables modularity in large projects.

Exercise Write the module skeleton

Add prototype declarations for the six helpers: int str_len(const char *s);, int str_is_empty(const char *s);, int num_abs(int n);, int num_sign(int n);, int arr_max(int *a, int n);, int arr_sum(int *a, int n);. Write int main(void) and inside it print "Modül hazır" with printf.

Show example solution

#include <stdio.h>

int str_len(const char *s);
int str_is_empty(const char *s);
int num_abs(int n);
int num_sign(int n);
int arr_max(int *a, int n);
int arr_sum(int *a, int n);

int main(void) {
    printf("Modül hazır\n");
    return 0;
}

Test yourself

Where are function declarations kept in C?
- In a .txt plain file
- In a .c source file
- In a .o object file
- In a .h header file
Show answer

In a .h header file — Declarations go in .h headers; definitions in .c sources.

Complete the str_len prototype

int str_len(const char ____);

Show answer

int str_len(const char *s);

Match helpers to purpose

str_len

String length
num_abs

Absolute value
arr_max

Largest element
arr_sum

Array sum

Next lesson: String helpers

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