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Putting it together

  • C course
  • Intermediate
  • Lesson 69/116
  • 6 min

Combine the library modules with a menu.

Putting it together with a menu

In the final step you combine all modules under a menu. The menu_run(Library *lib, int choice) function acts on choice: 1 lists all books, 2 checks out, 3 searches.

A switch (choice) branches the flow. Each case calls the relevant function. This structure is the skeleton of a real console app. In main we call the menu with fixed choices to test the output; in a real app you'd read the choice with scanf. In this final lesson all pieces come together: model, collection, checkout and search.

menu_run implementation

The void menu_run(Library *lib, int choice) function branches with switch. case 1: loop and print_book for all books. case 2: call checkout(&lib->books[0]). case 3: use find_by_title to search.

In main start with Library lib;, add a book, then call menu_run(&lib, 1);. This runs the menu's listing option. All modules meet here: print_book, library_add, checkout and find_by_title. The five-lesson project is complete; you have the skeleton of a real C console app.

Practice Integrate with menu_run

Add void menu_run(Library *lib, int choice) to the existing code. With switch (choice) add case 1: for (int i = 0; i < lib->count; i++) print_book(&lib->books[i]); and break;. In main add a book and call menu_run(&lib, 1);.

Starter code

main.c
#include <stdio.h>
#include <string.h>

typedef struct {
    char title[64];
    int year;
    int borrowed;
} Book;

typedef struct {
    char name[64];
    int id;
} Member;

typedef struct {
    Book books[10];
    int count;
} Library;

void library_init(Library *lib) {
    lib->count = 0;
}

void library_add(Library *lib, Book b) {
    lib->books[lib->count++] = b;
}

void print_book(Book *b) {
    printf("Book: %s (%d)\n", b->title, b->year);
}

int checkout(Book *b) {
    if (b->borrowed) return 0;
    b->borrowed = 1;
    return 1;
}

int return_book(Book *b) {
    if (!b->borrowed) return 0;
    b->borrowed = 0;
    return 1;
}

Book *find_by_title(Library *lib, const char *title) {
    for (int i = 0; i < lib->count; i++) {
        if (strcmp(lib->books[i].title, title) == 0) return &lib->books[i];
    }
    return NULL;
}

int main(void) {
    Library lib;
    library_init(&lib);
    Book b1 = {"C Tutorial", 2024, 0};
    library_add(&lib, b1);
    Book *found = find_by_title(&lib, "C Tutorial");
    if (found) print_book(found);
    return 0;
}

// Write menu_run function: switch with case 1 listing
// In main: call the menu with choice 1

Sample solution

main.c
#include <stdio.h>
#include <string.h>

typedef struct {
    char title[64];
    int year;
    int borrowed;
} Book;

typedef struct {
    char name[64];
    int id;
} Member;

typedef struct {
    Book books[10];
    int count;
} Library;

void library_init(Library *lib) {
    lib->count = 0;
}

void library_add(Library *lib, Book b) {
    lib->books[lib->count++] = b;
}

void print_book(Book *b) {
    printf("Book: %s (%d)\n", b->title, b->year);
}

int checkout(Book *b) {
    if (b->borrowed) return 0;
    b->borrowed = 1;
    return 1;
}

int return_book(Book *b) {
    if (!b->borrowed) return 0;
    b->borrowed = 0;
    return 1;
}

Book *find_by_title(Library *lib, const char *title) {
    for (int i = 0; i < lib->count; i++) {
        if (strcmp(lib->books[i].title, title) == 0) return &lib->books[i];
    }
    return NULL;
}

void menu_run(Library *lib, int choice) {
    switch (choice) {
        case 1:
            for (int i = 0; i < lib->count; i++) print_book(&lib->books[i]);
            break;
    }
}

int main(void) {
    Library lib;
    library_init(&lib);
    Book b1 = {"C Tutorial", 2024, 0};
    library_add(&lib, b1);
    menu_run(&lib, 1);
    return 0;
}

Expected output

Book: C Tutorial (2024)

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What does menu option 1 do?

  • Checks out
  • Exits
  • Searches
  • Lists books Correct answer

Explanation: Option 1 lists all books via print_book.

2 Complete the switch case

Question 
switch (choice) {
case 1:
    for (int i = 0; i < lib->count; i++) ____(&lib->books[i]);
    break;
}
Answer 
switch (choice) {
case 1:
    for (int i = 0; i < lib->count; i++) print_book(&lib->books[i]);
    break;
}

Explanation: case 1 prints each book with print_book.

3 Match menu options

Term Meaning
case 1 List books
case 2 Check out
case 3 Search
default Unknown choice

All lessons in Intermediate

1 Advanced pointers

  1. Pointer to pointer
  2. Array of pointers
  3. Function pointers
  4. Function pointer parameter
  5. void pointer
  6. Summary - Advanced pointers

2 Memory management

  1. Dynamic array
  2. Resize with realloc
  3. Memory leaks
  4. Dangling pointers
  5. Allocation patterns
  6. Summary - Memory management

3 Project: Helper library

  1. Module design
  2. String helpers
  3. Number helpers
  4. Array helpers
  5. Putting it together

4 Advanced string handling

  1. Dynamic strings
  2. String concatenation
  3. String search
  4. String conversion
  5. String safety
  6. Summary - Advanced strings

5 Function pointers

  1. Function pointer definition
  2. Calling function pointers
  3. qsort
  4. Callback patterns
  5. Function pointer array
  6. Summary - Function pointers

6 Advanced structs

  1. Structs and pointers
  2. Dynamic struct
  3. Struct and function
  4. Nested structs
  5. Array of structs
  6. Summary - Advanced structs

7 Unions and enums

  1. union
  2. enum
  3. Struct and union
  4. typedef enum
  5. Bit fields
  6. Summary - Unions and enums

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 File I/O

  1. FILE and fopen
  2. fprintf and fscanf
  3. fgets and fputs
  4. fclose
  5. fread and fwrite
  6. Summary - File I/O

10 Error handling

  1. errno
  2. perror
  3. strerror
  4. assert
  5. Error return values
  6. Summary - Error handling

11 Multi-file projects

  1. Headers and sources
  2. extern
  3. static
  4. Makefile basics
  5. Multiple modules
  6. Summary - Multi-file

12 Project: Library app

  1. Model design
  2. Library module
  3. Checking out
  4. Search and filter
  5. Putting it together

13 Dynamic data structures

  1. Linked list
  2. Adding to list
  3. Traversing list
  4. Deleting from list
  5. Stack and queue
  6. Summary - Dynamic data

14 Variable arguments

  1. stdarg.h
  2. va_start and va_end
  3. printf-like function
  4. vsnprintf
  5. Variadic patterns
  6. Summary - Variable arguments

15 Standard library

  1. stdlib.h
  2. string.h
  3. math.h
  4. time.h
  5. ctype.h
  6. Summary - Standard library

16 Command-line arguments

  1. argc and argv
  2. Argument processing
  3. getopt
  4. Argument validation
  5. Exit codes
  6. Summary - Command line

17 Debugging

  1. gdb basics
  2. Breakpoints
  3. Watch and print
  4. valgrind
  5. printf debugging
  6. Summary - Debugging

18 Advanced bitwise

  1. Bit masking
  2. Set and clear bits
  3. Bit shifting
  4. Bit hacks
  5. Pack and unpack
  6. Summary - Advanced bitwise

19 Advanced typedef

  1. typedef and struct
  2. typedef and function pointer
  3. typedef and array
  4. Opaque types
  5. typedef and enum
  6. Summary - Advanced typedef

20 Intermediate final

  1. Project design
  2. Data model
  3. Functional logic
  4. File I/O
  5. Putting it together