fptr in c code example

Example 1: fseek function in c

FILE* fp;
// if file is 50 bytes long:
fseek(fp, /* from the end */ 23, SEEK_END); // <- at 50 - 23 so 27
fseek(fp, /* from the start */ 23, SEEK_SET); // 23
fseek(fp, /* from the the current (see ftell) */ 10, SEEK_CUR); // 33

Example 2: what is -> in c

arrow operator ( -> ) in C is used to access a member of a 
struct which is referenced by the pointer in question