A structure type is usually defined near to the start of a file using a typedef statement. typedef defines and names a new type, allowing its use throughout the program. typedefs usually occur just after the #define and #include statements in a file.
Here is an example structure definition.
typedef struct {
char name[64];
char course[128];
int age;
int year;
} student;
This defines a new type student variables of type student can be declared as follows.
student st_rec;
Notice how similar this is to declaring an int or float.
The variable name is st_rec, it has members called name, course, age and year.