Structures can be easily used as a function parameters. It is done similar as with variables.

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1 1. Structures in functions. Structures can be easily used as a function parameters. It is done similar as with variables. #include <string.h> char title[50]; char author[50]; char subject[100]; int book_id; Books; /* function declaration */ void printbook( Books book ); int main(void) Books Book1; /* Declare Book1 of type Books */ Books Book2; /* Declare Book2 of type Books */ /* book 1 specification */ strcpy( Book1.title, "Heaven's Devisl"); strcpy( Book1.author, "William C. Dietz"); strcpy( Book1.subject, "Starcraft novel"); Book1.book_id = ; /* book 2 specification */ strcpy( Book2.title, "Misery"); strcpy( Book2.author, "Stephen King"); strcpy( Book2.subject, "Psychological thriller"); Book2.book_id = ; /* print Book1 info */ printbook( Book1 ); /* Print Book2 info */ printbook( Book2 ); void printbook(books book) printf( "Book title : %s\n", book.title); printf( "Book author : %s\n", book.author); printf( "Book subject : %s\n", book.subject); printf( "Book book_id : %d\n", book.book_id); printf( "\n");

2 2. Structural arrays. Standard C arrays are composed of simple type elements. It is possible to create an array that is more complex. To do so, one can use structures. The main idea of a structural array is to create a parallel set of arrays. int id_nr; float grade; students; int main(void) int i; float avarage; // declaration of the structural array students list[5]= 1001, 5.0, 1002, 4.5, 1003, 2.0, 1004, 3.5, 1005, 5 ; // display of the student data for(i=0; i<5; i++) printf("id Number: %d; Grade: %2.1f;\n\n", list[i].id_nr, list[i].grade); // grades avarage value calculation avarage = 0; // zeroing integrals is very important ;) for(i=0; i<5; i++) avarage += list[i].grade; avarage /= ++i; printf("avarage grade value: %3.2f\n", avarage); As one can see in the example, structure students has two data type definitions. When structural array was declared, it created two arrays: list[].id_number and list[].grade. If a structure had more data type definitions, the amount of the parallel arrays would be relatively larger.

3 3. Pointers to structures. Pointers connected to structures are created very similar as the ones used with variables or arrays. To declare a pointer to structure one should remember an important thing: how the structure was declared. If a structure was declared by typedef the pointer declaration is quicker. Declaration of a pointer to structure: Structure declared by typedef: random_structure_name *structure_pointer; Structure declared classically: struct random_structure_name *struct_pointer; To find the address of a structure variable, place the & operator before the structure's variable name as follows: struct_pointer = &variable_name; To access the members of a structure using a pointer to that structure, you must use the -> operator: struct_pointer->title;

4 #include <string.h> char title[50]; char author[50]; char subject[100]; int book_id; Books; /* function declaration */ void printbook(books *book ); int main(void) Books Book1; /* Declare Book1 of type Books */ Books Book2; /* Declare Book2 of type Books */ /* book 1 specification */ strcpy( Book1.title, "Klamca"); strcpy( Book1.author, "Jakub Cwiek"); strcpy( Book1.subject, "Godly fantasy"); Book1.book_id = ; /* book 2 specification */ strcpy( Book2.title, "Toy Wars"); strcpy( Book2.author, "Andrzej Ziemianski"); strcpy( Book2.subject, "PMC action adventure"); Book2.book_id = ; /* print Book1 info by passing address of Book1 */ printbook( &Book1 ); /* print Book2 info by passing address of Book2 */ printbook( &Book2 ); void printbook(books *book ) printf( "Book title : %s\n", book >title); printf( "Book author : %s\n", book >author); printf( "Book subject : %s\n", book >subject); printf( "Book book_id : %d\n", book >book_id); printf( "\n");

5 4. Bit fields. Bit fields are used for memory savings. It allows for packing data in a structure. It is used when a program has a limited amount of memory that it can use. The name bit field is referring to the function of bit fields. Basically bit fields are shortening the data type size to a number of bits. unsigned int f1:1; unsigned int f2:1; unsigned int f3:1; unsigned int f4:1; unsigned int type:4; unsigned int my_int:9; packed_struct; int main (void) packed_struct pack; pack.f1 = 1; pack.f2 = 2; pack.f3 = 3; pack.f4 = 4; pack.type = 234; pack.my_int = 5678; printf("f1: %d; \n", pack.f1); printf("f2: %d; \n", pack.f2); printf("f3: %d; \n", pack.f3); printf("f4: %d; \n", pack.f4); printf("type: %d; \n", pack.type); printf("my_int: %d; \n", pack.my_int); One can see that some displayed values differ from the declared ones. It is because the declared values are over the size range of a bit field, therefore the maximal value is set.