Module design
- C course
- Intermediate
- Lesson 13/116
- 6 min
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.
Practice 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.
Starter code
#include <stdio.h>
// helpers.h bildirimleri:
// str_len, str_is_empty, num_abs, num_sign, arr_max, arr_sum
// main: "Modül hazır" yazdırSample 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;
}Expected output
Modül hazır
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 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 Correct answer
Explanation: Declarations go in .h headers; definitions in .c sources.
2 Complete the str_len prototype
int str_len(const char ____);int str_len(const char *s);Explanation: const char *s is a pointer to an immutable string.
3 Match helpers to purpose
| Term | Meaning |
|---|---|
str_len |
String length |
num_abs |
Absolute value |
arr_max |
Largest element |
arr_sum |
Array sum |